IACAPAP Textbook of Child and Adolescent Mental Health

INTRODUCTION

Chapter

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NORMAL DEVELOPMENTINFANCY, CHILDHOOD AND
ADOLESCENCE
Nancy G Guerra, Ariel A Williamson & Beatriz Lucas-Molina

Watoto Wema boys enjoying a game in Kenya(Photo: Dennis Machio-Michezo Afrika)

Nancy G Guerra EdD
Associate Dean for Research,
College of Arts and Sciences;
University of Delaware,
Newark, DE, USA
Conflict of interest: none
declared

Ariel A Williamson MA
University of Delaware,
Newark, DE, USA
Conflict of interest: none
declared

Beatriz Lucas-Molina PhD
La Rioja University, Spain
Conflict of interest: none
declaredThis publication is intended for professionals training or practicing in mental health and not for the general public. The opinions
expressed are those of the authors and do not necessarily represent the views of the Editor or IACAPAP. This publication seeks todescribe the best treatments and practices based on the scientific evidence available at the time of writing as evaluated by the authorsand may change as a result of new research. Readers need to apply this knowledge to patients in accordance with the guidelines andlaws of their country of practice. Some medications may not be available in some countries and readers should consult the specific drug
information since not all dosages and unwanted effects are mentioned. Organizations, publications and websites are cited or linked toillustrate issues or as a source of further information. This does not mean that authors, the Editor or IACAPAP endorse their content or
recommendations, which should be critically assessed by the reader. Websites may also change or cease to exist.
©IACAPAP 2012. This is an open-access publication under the Creative Commons Attribution Non-commercial License. Use,
distribution and reproduction in any medium are allowed without prior permission provided the original work is properly cited andthe use is non-commercial. Send comments about this book or chapter to jmreyATbigpond.net.au
Suggested citation: Guerra NG, Williamson AA, Lucas-Molina B. Normal development: Infancy, childhood, and adolescence. In
Rey JM (ed), IACAPAP e-Textbook of Child and Adolescent Mental Health. Geneva: International Association for Child and Adolescent
Psychiatry and Allied Professions 2012.

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IACAPAP Textbook of Child and Adolescent Mental HealthA

15-year-old girl starts throwing nightly tantrums if she doesn’t get desert
after dinner. Her mother is justifiably concerned and seeks the help of amental health professional. Yet when her three-year-old son does the samething, she sends him to his room, convinced this is a passing phase he will outgrow
in due time. The mother probably is right—the same behavior has very different
meanings for toddlers and teenagers. Without a working knowledge of normal
development the same mother might send the three-year-old to a therapist or the
teenager to her room.
For parents, this knowledge comes from multiple sources including
experience, friends, cultural traditions, magazines and books, support networks,
and more recently electronic sources such as websites and chat rooms. Parents
also rely on guidance counselors, social workers, therapists, and physicians to help
them understand typical and atypical behaviors. Yet health professionals often
are more versed in the language of abnormality and psychopathology than in thelanguage of normal growth and development. For example, the Diagnostic andStatistical Manual for Mental Disorders (DSM-IV-TR) and the International
Statistical Classification of Diseases and Related Health Problems (ICD), provide
clinicians with a compendium of criteria and categories for aberrant psychologicaldevelopment. However, these systems provide little information about normal
development, which is not simply the absence or opposite of psychopathology.
The purpose of this chapter is to give a brief overview of normal childdevelopment, defined as average or “on-time” growth based on the attainment ofspecific physical, cognitive, linguistic, social-emotional, and behavioral milestones
across specific stages. A focus on normal development suggests what is likely basedon population averages, with clear historical, cultural, and international variations
to be expected. A foundational understanding of average development can be
useful to practitioners in many ways, from assisting clinicians in history taking orplanning diagnostic work at intake to augmenting case conceptualization and theselection of developmentally-appropriate treatments (Holmbeck et al, 2010).
This chapter begins with a review of key developmental principles orthemes, including nature versus nurture, developmental timing and plasticity,
critical and sensitive periods, and the role of culture and context. Following thisbrief introductory section, age-specific milestones in cognitive, linguistic, socialemotional, and behavioral development from infancy through adolescence arereviewed. Although it is also important to understand normative milestones in
the area of physical development, this typically is covered in medical and healthpublications and is beyond the scope of this chapter.

UNDERSTANDING NORMAL DEVELOPMENT
Several recurring developmental principles or themes are important tokeep in mind when defining normal development and identifying growth processes
and milestones.
Nature versus nurture: the origins of development
There has been a long history of debate about the influence of nature versus
nurture on development, often referred to as the “nature-nurture debate.” Are weborn a certain way or does our behavior depend on how we are raised? A focus on
nature highlights the role of genes and biology in predetermining developmental

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IACAPAP Textbook of Child and Adolescent Mental Healthoutcomes from conception onward. In contrast, a focus on nurture emphasizes therole of life experiences across different contexts including the family, school, peergroup, community, and culture.
Recent advances in behavior genetics have provided compelling evidence
for the relative contributions of both nature and nurture. In light of these scientificadvances, few current theories of development embody an either/or position inthis debate, but emphasize the interplay of both over time (Berk, 2006). Statedsimply, a key issue is not whether development is due to nature or nurture, but
how much and how each contributes to outcomes across multiple characteristics
and domains. Rather than consider nature versus nurture, it is more accurate toconsider both nature and nurture and how they interact (Plomin et al, 1995).
The empirical evidence on the relative contribution of nature and nurture
comes largely from family, twin, and adoption studies, as well as from more recent
DNA analyses. Much of the research on the genetic roots of behavior has focusedon disorders or problem behaviors, including mental retardation, schizophrenia,
autism, alcoholism, aggression, and criminality. A strong relation between biology
and development has been found for chromosomal and single-gene disorders
such as Trisomy 21 (Down’s Syndrome). The genetic contribution for disorders
involving multiple genes is more complex to determine with estimates varying
widely across studies. For example, heritability estimates for alcoholism have beenfound ranging from 0.32 to 0.98, depending on symptoms (McGue, 1994). In any
case, the influence of environmental factors such as parenting styles, socioeconomic
status, and neighborhood characteristics on mental illness, behavioral disorders,and other individual differences looms large (Meier et al, 2008; Turkheimer et al,
2003; Tuvblad et al, 2006).
What do we know about the role of nature and nurture in children’s normal
development? Much of this work has focused on two areas: temperament andintelligence. Studies of infants and young children have examined temperamental
characteristics such as reactivity, mood, shyness, sociability, emotionality, attention/
persistence, and adaptability. Because temperament is defined as stable and early
appearing individual differences in behavioral tendencies, it is presumed to havestrong biological roots. Clearly identifiable and enduring patterns of behavior suchas shyness have been observed in very young infants, suggesting children are bornwith these tendencies. Twin studies generally confirm this genetic contribution,with heritability estimates ranging from 0.20 to 0.60 (Saudino, 2005). Intelligencealso has a high heritability factor, typically estimated to be about 0.50 (Plomin
et al, 1995); however, this may vary according to environmental differences likesocioeconomic status (Turkheimer et al, 2003).
But findings for both temperament and intelligence also mean that muchof what differentiates individuals is not accounted for by a child’s biological birthcertificate. Some of these environmental influences vary between contexts. For
instance, communities vary in terms of resources and families differ in termsof typical parenting practices. However, it is also important to remember thatenvironmental influences within a given setting may be non-shared. For example,
parents may treat their children differently within the same family—this is called
the “non-shared environment.”
As mental health professionals consider the extent of their child clients’normal or atypical development, it is important to recognize this complex interplayof nature and nurture and how this contributes to the clients’ clinical presentations.
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Additionally, educating youths’ primary caregivers about the biological andenvironmental influences on development may dispel the misconception thatchildren are products of either nature or nurture in isolation. A boy who is “justlike his father” may have been born with some genetic similarities, but he also isequally likely to be modeling his father’s behavior based on what he sees at homeand elsewhere.
Developmental timing and plasticity
A second overarching theme within the developmental literature is thesequencing and variation within normative development. A continuous view ofdevelopment holds that humans grow and change through a gradual process,growing at a relatively even pace and acquiring more complex cognitive, linguistic,social-emotional, and behavioral skills in a linear fashion as they age, much likegradually climbing a hill. Discontinuous theories conceptualize development
in a stage-specific pattern, where individuals experience rapid change whentransitioning from stage to stage, but experience relatively little change during one
developmental period, much like climbing stairs.
Just as the nature versus nurture debate shifted towards a nature and nurture
perspective, theories of development have increasingly blended continuous anddiscontinuous models of development. The end result is that development is seen asa dynamic process that can be characterized as both continuous and discontinuous
in its pattern and rate of change. Accordingly, normal child development occurs on
a continuum, ranging from children whose physical, cognitive, social-emotional,
and behavioral development may lag behind those of their peers, to children who
are precocious, meeting or surpassing developmental milestones before mostchildren their age. Even still, a majority of children who develop slightly earlier orlater than their peers may do so within a “normal” timeframe.
As opposed to either maintaining a steady developmental pace or maturing
through a rapid series of developmental “bursts,” children demonstrate considerable

Imitation: a quick way ofacquiring skills

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IACAPAP Textbook of Child and Adolescent Mental Healthheterogeneity in their rate of development. Such variation occurs within and between
different developmental domains, with varying rates of development in cognitive
versus social-emotional domains, for example, as well as across different periodsof youth development, such as in toddlerhood versus adolescence (Holmbeck etal, 2010). Whereas one child may demonstrate advanced linguistic development
during toddlerhood, he or she may lag behind some children in developing motor
coordination at this time. During adolescence, this same child could have verbal
abilities that are commensurate with peers, while also demonstrating highly
advanced motor coordination compared to others.
It is useful to keep in mind that, barring early mental or physical disorders,lapses in development and deviations from the norm at different points in time
are not necessarily predictive of subsequent developmental deficits or delays.
Instead, children typically continue to grow and change. Traits or skills can bealtered throughout the lifespan although they typically are more malleable earlier
in development. This notion of plasticity is an important characteristic of normalchild development.
Critical and sensitive periods
One of the most famous cases in the developmental literature is abouta child named Genie who was locked in a closet until she was discovered byauthorities at age 13. Although Genie was the subject of intensive intervention,
she was never able to regain normal cognitive, physical or social skills. Studies ofGenie and other feral children, individuals who have lived isolated from humancontact from an early age, have yielded important information about critical
periods for normal development. A critical period is a limited time that begins
and ends abruptly during which a specific function develops. If the conditions fordevelopment are not available during that time, it may be extremely difficult oreven impossible to develop these functions later in life. For example, the first five
years of life are a particularly critical period for language acquisition. The earlyyears are also critical for the development of vision—studies of babies born withcataracts left unrepaired have found that they do not develop normal vision even if
cataracts are removed later in life.
A sensitive period is a time when it is easiest for children to acquire certain
skills. It is similar to a critical period in that it is a time of optimal development,
but it is best understood as a time of maximum sensitivity that begins and ends
more gradually and is more amenable to recovery. For example, second language
learning is easier before age 6, but not impossible at any age (although most older
learners do not speak with a native accent). The difference between critical andsensitive periods has also been the subject of much debate, particularly in the areaof language. It is sometimes blurred, particularly because critical periods have been
defined as times when individuals are most “sensitive” to stimuli. Critical andsensitive periods are best understood as optimal “windows of opportunity” and areimportant for encouraging positive developmental outcomes that are most likely(and possibly can only occur) during certain ages.

Critical period
A critical period is alimited time that begins
and ends abruptly during
which a specific function
develops. If the conditions
for development are notavailable during that time it
may be extremely difficult
or even impossible todevelop these functions
later in life.
Sensitive period
A sensitive period is atime when it is easiest
for children to acquire
certain skills. It is similar
to a critical period in that
it is a time of optimal
development, but it is best
understood as a time of
maximum sensitivity thatbegins and ends more
gradually and is moreamenable to recovery.

The role of culture and context
Normal development can only be understood within the context andculture where it occurs. These factors can influence normal development and may
promote or hinder it. Thus, another important principle of normal development

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IACAPAP Textbook of Child and Adolescent Mental Healthis that average population rates for on- or off-time development may varyconsiderably within and across racial/ethnic and cultural groups. They may also
vary according to other contextual differences including historical era, community,
or socioeconomic status. For example, during the colonial period in the US,
parents considered babies crawling to be something abnormal and to be avoided
at all costs. Doctors at that time even recommended that parents tie their children
to a cradle to prevent crawling as this movement was thought to be reflective of
animal and not human behavior. Now, most American parents are delighted when
they see their children beginning to crawl and try to encourage it.
The nature and timing of some capabilities is less likely to vary acrosscontext, particularly in physical and cognitive domains. Skills and behaviors—such as cooing and babbling, initiation of speech, or the ability to use abstract
reasoning—develop in a more species-specific pattern; they are all capabilities
that are unlikely to differ cross-culturally. For example, children in India, China,
Sweden, and Peru all are likely to begin to talk during the second year of life,
although cultural practices may encourage or discourage the precise timing of
language development. Similarly, if a child grows up in a culture that does notencourage abstract thinking, although this potential develops during adolescence,
it may never translate to actual behavior.
This means that normal development must always be understood within a
specific culture or context that regulates its expression. However, this framework
can also present challenges. For example, immigrant parents often expect theirchildren to conform to standards of normal behavior in their home country whilechildren try to assimilate to their new culture. Children and parents must also
conform to standards that may be considered normal in their home country
that may even be illegal in their new country. For this reason it is important forpractitioners to understand the cultural norms of their clients and how they canbest align with acceptable practices.

Child development isorganized into:••••

Infancy: 0 to 2 years
Toddlerhood andpreschool: 2 to 5
Childhood: 6 to 11
Adolescence: 11 to
18.

STAGES AND DOMAINS OF DEVELOPMENT
The following sections describe age-graded milestones across different
domains of development. Child development is organized into infancy (ageszero to two), toddlerhood and preschool years (ages two to five), childhood (agessix to 11), and adolescence (ages 11 to 18). Although in this chapter we do notdiscuss development during emerging adulthood (ages 19 to 29), in many cultures,
particularly in higher income Western countries, this period is considered to be acontinuation of adolescence as part of an extended transition to adulthood.
Cognitive development focuses on changes and growth in internal mental
processes, such as concrete and abstract thinking and reasoning, problem-solving,
memorizing and recalling, planning, imaging and creating. Cognitive development
also refers to the proliferation of internal cognitive scripts or patterns of thinking
and understanding, as well as larger schemas, or overarching beliefs about theself, others, and how the world works. Milestones that are categorized as part ofthe linguistic development domain reference the child’s communication skills,
developing speech patterns, and sentence structuring, much of which relates to thesequencing of cognitive development.

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The social-emotional domain involves the development of relationships withothers and the learning of social norms and customs, as well as growth in the ability
to identify, understand, express, and modulate one’s feelings. Behavioral milestones
refer broadly to the child’s development of age-appropriate behavior, such as
following rules or regulating deviant behavior. Throughout infancy, toddlerhood,childhood, and adolescence, normally developing youth negotiate certain tasks or
milestones that occur at specific time points, in each of the cognitive, linguistic,social-emotional, and behavioral domains.

NORMAL DEVELOPMENT IN INFANCY AND EARLYTODDLERHOOD:
AGE ZERO TO TWO
From birth to age two, interactions and patterns of attachment between theinfant and the primary caregiver are an important catalyst for cognitive, linguistic,social-emotional, and behavioral development. Noticeable developmental changes
occur rapidly during the infancy period, particularly when comparing thecompletely dependent child at birth to a child at age two who is able to put words
together, walk alone, and navigate the social environment with purpose.
For this reason, milestones within each domain in the following sections
are organized according to the period of birth to six months, seven months to 1
year, 13 months to 18 months, and 19 months to two years, to better reflect thesequencing of change during the infancy and early toddlerhood periods. Recall
that the descriptions and temporal placement of these milestones generally reflectnormal development, but that infants who complete these milestones slightly
before or after their same-age peers can still do so within the bounds of what is
considered to be normal development.
Cognitive and linguistic milestones
Birth to six months
During this period, the infant’s use of sight, sound, taste, touch, and smell
facilitates cognitive and linguistic growth as well as social interaction with primary
caregivers. From birth to six months, infants’ perceptual acuity begins to improve,leading to the increased differentiation of external stimuli, such as patterns, colors
or sounds, as well as the recognition of facial expressions. As they navigate their
new world, babies are attracted to stimuli that help them in this quest—brightly
colored mobiles, clear sounds like bells and whistles and easy to distinguish shapes
and patterns.
These perceptual changes coincide with the infant’s growing preference forfamiliar people and stimuli. At birth, most babies tolerate being held by a numberof different adults without showing too much distress. However, closer to age six
months, babies may cry or whimper more often when held by unfamiliar adults
or family members, developing a particular preference for the face, vocal sounds
and smell of the primary caregiver, typically the mother in most cultures. In somesense, normal developmental processes during infancy suggest it might be easier fora child to start communal care arrangements like day care at a relatively youngerage (earlier than six months) before developing clear preferences for caregivers or
settings.

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IACAPAP Textbook of Child and Adolescent Mental HealthDuring this stage, infants also develop a preference for face-to-faceinteractions and are able to recognize and imitate adult facial expressions. This
recognition and imitation typically is quite pleasing to parents and increases theparent-child bond as reciprocal interactions become possible. The infant’s memory
and attention skills likewise improve, so that the infant can efficiently remember
and attend to certain people, physical locations or objects, such as a bottle or apreferred toy. In essence, during these very early months, the infant is constructing
a blueprint for life—filled with familiar objects, people and experiences.
A common concern for parents during this stage is why their babies cry
so frequently—during the night, multiple times per day and even after being
fed. Yet, without the ability to talk, crying is a normal and primary venue forcommunicating discomfort to caregivers—babies are born crying. Infants cry
primarily to express basic needs, such as hunger, thirst, or the desire for comfort,
as well as to express negative emotional or physical states, such as anger or pain.
Indeed, as parents become more synchronized with their infants, they soon areable to recognize different types of cries, based on the crying pattern, intensity andrhythm. For example, basic crying is a cry that increases in intensity and rhythm
in response to hunger, whereas angry crying and pain crying, are characterized by along cry followed by a period of silence and rapid inhalations, usually beginningsuddenly and in response to physical discomfort (Hetherington et al, 2006).

CryingCrying is a normal
and primary venue forcommunicating discomfort
to caregivers. Infants cry to
express basic needs, suchas hunger, thirst, or thedesire for comfort, as well
as for anger or pain.

Cultural and contextual differences may also impact babies’ crying patterns.
It has been reported that infants from non-Western countries are quieter thantheir counterparts from Western countries (Zeifman, 2001). An examination of
infant caregiving practices in these societies suggests that the greater amount ofphysical contact and the more frequent feedings typical of non-Western parenting
habits may physiologically prevent infants from crying. Contextual stressors, suchas poverty, can impact important child rearing necessities like food and housing,which may influence parental responsiveness and, in turn, babies’ crying. A lackof food, housing, or financial security can make it difficult for parents to provide
sensitive, responsive and stimulating care to their children. Therefore, the extent
to which parents effectively perform their caregiving roles depends not only on
their ability to recognize and respond successfully to their babies’ cries, but also on
stresses and supports they are provided contextually. For this reason, practitioners
and health workers should be especially aware of such stressors in order to support
parents who are learning to respond to crying newborns, so as not to become an
additional source of stress for the family.
To the relief of many parents, by about two months of age babies also begin
cooing, making noises that are characterized by short vowel sounds, and move into
babbling by four months, when consonant sounds are added and speech becomes
repetitive, for example, “babababa.” Although crying does not stop at this time,cooing and babbling noises are pleasant and fun for parents to hear. They also serve
as precursors to language development.
In addition to a preference for the voice of the caregiver, the infant alsoprefers to hear his or her native language and may begin communicating about
the same items or events as the primary caregiver in a process called joint attention(Berk 2006). At the infant’s birth, a new mother may point to an older sibling
and tell the infant, “That’s your brother!” At that early age, the infant typically

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IACAPAP Textbook of Child and Adolescent Mental Healthwould not direct attention towards the brother at that time. When the parent
utters this same sentence when the infant is closer to six months, the infant may
look at the brother and babble or coo, showing interest in the same subject as theprimary caregiver. This joint attention with the caregiver can enhance vocabularydevelopment, and also demonstrates the infant’s growing and related cognitive
abilities. Parents at this time may start pointing out various environmental objects,
people or events, directing the infant’s attention and integrating new vocabulary
words. Although at this stage, the infant will only change visual attention andmake cooing or babbling noises while engaging in joint attention, this process
becomes more established in later months and throughout toddlerhood. This also
points to the importance of social stimulation and interaction as a primary meansfor early development.
Age seven months to one year
Infants continue to use their growing perceptual and sensory capabilities toinform cognitive and linguistic development during this period as they approach
one year of age. At this time, infants’ memory and attention skills continue toimprove, although memory in these early stages is contingent upon the familiarityof the situation or person or the infant’s motivation, for example, to interact withothers or use a toy.
A milestone of this developmental period is object permanence, anunderstanding that objects or people still exist when these items are not readily

Object permanence
Is the understanding that
objects or people still exist
when they are not readily
seen or heard. Object
permanency emerges
around 8 months of age.

Infants need to develop a
relationship with at least one
primary caregiver for socialand emotional development
to occur normally. Proximity
between infants and an
attachment figure facilitates
this process.
Inuit mother and baby

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9IACAPAP Textbook of Child and Adolescent Mental Healthseen or heard, that emerges around eight months (Piaget, 1954). As an example,
imagine that two eager parents are playing with their three-month-old infant on
the floor, using a popular jack-in-the-box toy where the doll figure is hidden in a
box and pops out again to surprise the infant. The parents notice that the infant
acts as if the toy is gone when it is not directly in sight and only seems frightenedwhen the toy pops out. They wonder whether their baby is unable to play with this
toy or even whether something is wrong with their baby. Perplexed, they put the
toy in the closet. They decide to try again when their baby is about eight months
old and are pleased to see that their infant now searches for the jack-in-the-box
doll, babbles excitedly when it pops out and appears to remember the game andwhere the doll went time and time again. This baby will now also engage in turntaking and “peek-a-boo” games with caregivers, and will search for toys or otheritems that are out of sight, for example, when an item or toy is placed under ablanket or cloth.
At this stage, babies use babbling in conjunction with play throughthe manipulations of different sounds when interacting with the parent and incombination with gestural requests for objects. Infants may babble or make noises
to suggest they want something, such as a toy or food, and begin to point at objects
around age 1, as another form of communicating their desires. Some babies will
speak their first word during this period or during the 13 to 18 month stage.
Finally, infants will learn and respond to their own name at this point, which also
reflects social-emotional gains in differentiating the self from those around theinfant, and especially from the primary caregiver, although this process (self-other
differentiation) is more apparent after 13 months of age.
Age 13 months to 18 months
During this time period infants expand their repertoire of earlier cognitive
skills. Most babies not only search for objects hidden from sight—characteristic ofobject permanence—but look for these items in more than one location, such as
under the couch and in other rooms, making organized games like hide-and-seek
possible.

Click on the picture
to access a 2-hourroundtable discussion
about the development of
temperament.

Memory storage and retrieval continues to advance—babies at this age canimitate others with increasing delays between the time of the observed behavior
and the imitation of this behavior in other contexts. For example, at home, a father
may put a toy cup on his head playfully, using it like a hat. Later in the week, at
daycare or at the home or a relative, the 15-month-old infant may do the samething when presented with a toy cup while in a playroom, showing a delayed
imitation of the father’s home behavior. Infants at this age also begin to store priorexperiences in memory and are aware of times when present situations are not inaccordance with prior events or their pre-existing expectations. For example, whilechanging a 13-month-old baby’s diaper, the mother may give the baby a certain
object to keep the infant occupied, like a specific stuffed animal the baby likes tohold and squeeze during diaper change time. If the stuffed toy is unavailable oneday, the infant might still look expectantly at the mother and reach toward her,looking for the toy. The infant became accustomed to this routine and has noticed
that this diaper change is different from their typical routine.
Infants typically say their first word at 12 or 13 months, although theaverage range is between eight and 18 months. Many parents may expect their

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IACAPAP Textbook of Child and Adolescent Mental Healthchild to say “mama” or “dada” first, both of which are similar vowel-consonant
combinations to early babbling. However, infants’ first words may be based oncontext or the repetition of particular words that the caregivers say frequently
throughout the day. One mother wanted to teach her infant daughter to avoid
dangers and repeatedly said “no” during the day. Unfortunately, she was dismayed
when her daughter’s first word was “no” instead of “mama”—in fact, the daughter
started to call her mother “no” for some time.

Click on the pictures below
to watch developmental
theorist Jean Piaget
discuss and illustrate histheory about intellectual
development (in French
and English with subtitles
in English).

After the first word, vocabulary will grow to about 200 words during
this period, although this can vary substantially by the infant’s developmental
environment. Socioeconomic status and cultural background are two importantvariables that can impact language development and content, for example, howmany words children learn and whether these words are predominantly objectbased (referential) or expressive. For example, the infant who learned the word“no” soon went on to learn the parents’ names, calling them “mama” and “dada.”
Whereas referential words primarily are used to name things, expressive language
describes people, feelings or social events. Children of different demographic or
cultural groups may use either more referential or more expressive language during
early development, depending on their external environment in combination withother individual characteristics.

Part 1 (12:25)

Age 19 months to two years
As the infant approaches toddlerhood, cognitive advances continue in theareas of memory, problem solving and attention (executive functioning). Beginningat this stage, infants can develop and carry out action plans, such as building a
specific type of structure with blocks. Whereas 10-month-old children cannot
typically sustain play together—typically sit side by side in a playroom (called
parallel play)—the play of infants at this stage becomes more interactive. When apair of 20-month-old infants plays together, they might engage in pretend or makebelieve play. A common theme for make-believe play is engaging in everyday tasks
that the infants have observed others perform, such as eating, cooking, sleeping,or feeding household pets. This type of pretend play is also indicative of moreadvanced working memory and imitative skills—and perhaps another venue forconstructing a blueprint for life.
Cultural differences in children’s play themes have been well documented(Rogoff, 2003). Although most children will engage in ordinary chores likesweeping or food preparation cross-culturally, North American toddlers tend
to participate more frequently in make-believe play that includes managing
household machines such as vacuum cleaners and dishwashers, or using a mobile
cell phone. In contrast, Mayan children from Guatemala have less involvementwith machines but many have roles in adult activities, such as running errands to acorner store or weaving household items. The differences in themes of play acrosscultures highlight the fact that cultures and communities may vary considerably
in the skills that are considered important or a normal part of one’s household.
Likewise, practitioners should note that parents who are more informed about thebenefits of pretend play may take a more active role in introducing complexity anddiversity into play themes. Other parents may either be uninformed about play or
it may not be culturally relevant to be involved in children’s play activities. Overall,
the themes of play and the degree to which parents are involved in play differ

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Part 2 (13:05)

Part 3 (11:30)

Part 4 (4:49)

11

IACAPAP Textbook of Child and Adolescent Mental Healthacross cultures, and should be taken into account before making assumptions
about “normal” pretend play.
Along with the cognitive gains at this stage, this period brings several
advances in linguistic skills. Infants at this age start combining two or more words,
like “no mom!” or “want that,” and the infant’s vocabulary also grows noticeably.
Because children at this stage are learning and practicing word pronunciation, theyoften replace certain parts of a word with vowels of consonants that are easier to say
or leave off the end of words. During his first day of daycare, one infant constantly
asked for “ju” during lunchtime and became upset when the preschool teachers
tried to ask what this meant. When this infant’s father picked him up from daycarethat afternoon, he was able to explain to the teachers that this meant “juice,”reflecting the infant’s routine at home, where he got juice every day with his lunch.
In a Spanish-speaking country, such as Mexico, an infant might initially say “meloetá” instead of “caramelo está” in Spanish (“the candy is there,” in English) to her
granddad as she is trying to find the candy her granddad has playfully hidden awayfrom her. This infant has mispronounced part of the words and left off several
sounds. Although parents may express concern that their infant cannot form fullwords, this type of word replacement or shortening is typical for infants at thisstage.
Social-emotional and behavioral milestones
Just as infants depend primarily on caregivers to facilitate their explorationof the external environment and, by extension, their cognitive and linguistic
development, much of the infant’s social-emotional and behavioral milestones arenegotiated in the context of the infant’s relationship with the primary caregiver.
A critical milestone during this period is the development of the attachment
relationship, or the infant’s emotional bond to the primary caregiver (Ainsworth,1979). The strength of this bond indicates the extent to which the infant can use
the caregiver as a secure base from which to explore the world, return to during
times of distress, and use as a framework for social-emotional development.

Is it OK for parents andchildren to sleep together?
How long should they sharea bed?

Birth to six months
At this early stage, infants are learning to regulate their emotions andbehavior, although they may not seem to be very good at it. Part of self-regulation
includes the formulation of regular behavioral patterns in the areas of eating
and sleeping, for example, as these behaviors can also impact the infant’s level of
emotional arousal and degree of affect regulation. Although most babies will not
sleep through the night until they reach their first birthday, infant sleep cycles
become more predictable by the age of eight weeks, when infants are sleeping for
longer periods at night than during the day. It is important during this period
for parents to establish regular activities and routines—it is easier to learn to wait
for something that comes at the same time each day than for something that is
random.
Sleeping routines are often difficult for parents to establish and mayvary considerably by culture. Is it OK for parents and children to sleep together?
How long should they share a bed? Although the majority of American infants
typically sleep separately from caregivers in a crib, other cultures prefer co-sleeping
arrangements, where the infant sleeps with one or more caregivers in the same
bed, often with other siblings as well. For some cultures, co-sleeping is seen as

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IACAPAP Textbook of Child and Adolescent Mental Healthan important indication of the infant-caregiver bond and is presumed to have
health benefits over sleeping separately. These cultural variations are likely to be
reinforced in other practices—the important thing to remember is that infants
need routines, and that appropriate routines do vary cross-culturally.
Regardless of the varying sleep and wake cycles or patterns in a particular
culture, infants at this stage will begin to exhibit more predictable sleeping habits
and cycles. Similarly, eating schedules will become more predictable, with theinfant transitioning from feeding five to eight times per day in the first coupleof months after birth, to feeding three to five times per day, at relatively equalintervals, by the sixth month of life.
Just as routines are important for babies, infants can easily become
overwhelmed by new experiences, taxing their emerging self-regulation skills. For
example, imagine that a caregiver is dangling a brightly colored mobile over her
three-month-old infants’ face, making whooshing noises as she moves the mobile
parts above and around the infant’s head. After cooing and smiling for a few
seconds, the infant suddenly looks away, disengaging from the caregiver’s play.
Should the caregiver be upset? Did she do something wrong? Is there something
wrong with the infant?
Such behavior is normal at this stage of development. It is called gazeaversion, and is a normal reaction to overstimulation and arousal. In this case,the infant will look away from the stimuli—for example, turning away fromthe mother’s play with the mobile—as a method to regulate arousal. Over time,through appropriate and sensitive interactions with caregivers, infants’ tolerance
for emotional arousal and regulation of this arousal will increase. After becoming
habituated to the caregiver’s play with the mobile, this infant may begin to track themobile and coo at the caregiver for a longer period of time, eventually maintaining
this play.

Gaze aversion
Gaze aversion, looking
away from a stimulus,
is a normal reaction to
overstimulation and arousal
and is an infant’s attempt toregulate arousal.

The infant’s range of emotions increases during this period from thedichotomous states of either pleasure (relaxation) or pain (discomfort) to thedifferentiation of various feeling states within these broad categories. Emotional
expression becomes more varied, organized and specific to the infant’s external
environment and/or internal feeling state. During these months, the infant also
begins to match the caregiver’s feelings during face-to-face interactions. By theage of six weeks, the infant develops a social smile in response to human faces andparticularly the face of the primary caregiver. At three or four months, the infantalso begins to laugh, especially in response to the laughter of other adults or the
surprise at discovering a fun, novel situation, such as the caregivers making funny
faces at the infant. Frustration and the closely related emotional state of anger
become more distinguishable by about six months, at which point the distinct
state of sadness also emerges. Infants will typically withdraw when feeling sad,although crying and its distinct patterning can accompany a range of negative
emotional states. In truth, the multiple emotions infants display only six months
after birth are striking!
Parents often are surprised to learn that infants (and people) vary greatly
in temperament, defined as a biological predisposition to patterns of behavior andinteraction (Wachs, 2006). Imagine that several new mothers are sitting together
at a weekly playgroup with their six-month-old infants when one mother brings

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IACAPAP Textbook of Child and Adolescent Mental HealthPhoto: Linda Croninup several eating and sleeping issues she has been having with her baby. Her baby
has yet to develop routine sleeping and eating patterns and often cries in responseto new toys or situations that he is exposed too. Another mother mentions that she
has not had this experience at all, that her infant sleeps through the night and loves
exploring new objects and meeting new people. A third mother comments that she
is not sure whether her baby will be a social child later in life because the motherremembers being told that she was shy when she was a baby.

Temperament is a biologicalpredisposition to patterns of
behaving and interacting.

The three mothers wonder which of these babies is the most “normal”.
They all are! They are normal, just different. The first baby would be classified ashaving a difficult temperament, the second as easy, and the third as slow-to-warm
up. Babies who exhibit difficult temperament are those who are highly reactive
to external stimuli, expressing more negative emotions, such as anger, fear, or
anxiety, and are less likely to effectively manage or regulate those emotional states.
Irregular sleeping and eating habits are also associated with this category (Thomas& Chess, 1977). Easy infants are thought to have more regular eating and sleeping
habits and to adapt well to new situations or people; these infants are also lessemotionally reactive and express and regulate emotions and arousal states without
a predominance of negative emotionality. Finally, slow-to-warm-up infants may
initially appear more withdrawn than others, with mildly negative responses tonovel situations, but eventually exhibit positive and adaptable characteristics andpatterns of social responding to others.
Although temperament is thought to be a relatively stable and biologicallyinfluenced trait that can predict later social-emotional development, only 60% of
infants can be classified into a temperament category, and infant traits may changeover time. Indeed, temperament style has been found to interact with elements ofthe external environment, such as maternal responsiveness or family chaos, making

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IACAPAP Textbook of Child and Adolescent Mental Healthit difficult to reliably predict how temperament styles in infancy and toddlerhood
relate to later social-emotional development (Essex et al, 2011; Rubin et al, 2002).
Remember, the settings where children grow up will influence how they turnout—nature and nurture join forces to make us who we are and who we become.
Additionally, cross-cultural studies have shown differences in infant
temperament when comparing Western and non-Western populations (Ahadi &Rothbart, 1993). For example, North American infants typically score higher on
measures of activity level (intensity and frequency of motor movements), approachtendencies (degree to which a child accepts new people, objects or situations),
and positive mood (extent to which a child expresses positive emotions) whencompared to Chinese infants. Conversely, this line of research has shown that
Chinese infants are, on average, more easily consoled during a crying episode thantheir North American counterparts.
Age seven months to one year
The most apparent social-emotional and behavioral milestones during thisperiod are the development of the attachment relationship, and the occurrence of
stranger wariness and separation anxiety. Infant-caregiver attachment refers to theinfant’s bond with the primary caregiver, and the extent to which the infant can use
the caregiver as a secure base for exploration and for comfort. Researchers initiallyclassified attachment styles through a series of interactions called the “Strange
Situation task”, involving short separations from the primary caregiver andexposure to another adult in the context of an unfamiliar playroom (Ainsworth,1979).
Secure attachment refers to infants who cry when the primary caregiveris absent, but allow themselves to be comforted upon the caregiver’s return; these
infants also use their caregiver as a secure base which they periodically “check in
with,” by physically toddling back to or visually glancing over at the caregiver,during their exploration of new environments or situations. Separation anxiety canbe an overt sign of secure attachment, although not all infants evidence this typeof behavior and it may occur regardless of attachment classification (Berk, 2006).
Many primary caregivers express concern that at this age their children cannot
tolerate minor separations and begin crying inconsolably when the caregiver leaves,whether parents are leaving their child with unfamiliar adults in a new daycare
setting or in the care of familiar family members. This anxious behavior peaks
around one year of age, along with stranger wariness, in which the infant displays
discomfort in the presence of unfamiliar people. Although separation anxiety may
persist even after the infant develops a regular routine of separations from theprimary caregiver, for example, attending daycare five days per week, this behavior
is normal up until toddlerhood.
Insecurely attached infants fall into several categories, all of which reflectdisruptions in the infant-caregiver bond. Avoidant attachment characterizes infants
who do not become distressed when the caregiver leaves the room and react
to both strangers and the caregiver in a similarly unresponsive fashion. Infants
who exhibit resistant attachment are hesitant to explore an unfamiliar playroom
while the caregiver is present, become upset when she leaves and are angry andsometimes aggressive with the caregiver when she returns, showing some resistanceto being comforted. Disorganized attachment, a category created after several years

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Insecure attachment
Disruptions in the infantcaregiver bond can result in
insecurely attached infants.
This can manifest in:•
Avoidant attachment,
when infants do not
become distressed
when the caregiver
leaves the room andreact to both strangers
and the caregiver in asimilarly unresponsive
fashion.
•Resistant attachment,
which is characterisedby hesitancy to
explore an unfamiliar
playroom while thecaregiver is present,
become upset when
she leaves and are
angry and sometimes
aggressive with the
caregiver when she
returns, showing
some resistance tobeing comforted.
•
Disorganizedattachment,
when infants
appear confused,
contradictory or
emotionally labilein their behavior,
with some of these
infants showing signsof disassociation(frozen facial
expression and total
unresponsiveness).

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IACAPAP Textbook of Child and Adolescent Mental Healthof initial attachment research, represents infants who are confused, contradictory,or emotionally labile in their behavior, with some of these infants showing signs ofdisassociation (frozen facial expression and total unresponsiveness); this categoryreflects the most severe form of insecure attachment.
Although a healthy infant-caregiver relational bond is important,the attachment relationship and its influence on later development depend on
multiple individual and contextual factors. These include maternal sensitivity andresponsiveness, infant temperament, home environment, socio-economic status,
racial/ethnic background, and other influences in the infant’s life (Seifer et al,
1996; Wong et al, 2009).
The biological mother also is not necessarily the primary attachment figure;the infant may bond with other important adults, including fathers, extended family
members and foster parents. Attachment classifications also depend a great deal on
the infant’s cultural context. Attachment classifications and the Strange Situation
task are culture-bound phenomena, and may not adequately describe infantcaregiver attachment in other cultures. For example, suppose a Japanese infant andhis mother are placed in a Strange Situation task and the infant does not appear to
be distressed when his mother leaves the room. When a stranger comes in to playwith the infant, the infant is somewhat non-responsive and continues playing on
his own. This pattern persists when his mother returns to the room. Should thisinfant be classified as having an avoidant attachment pattern? Not necessarily;
infants in non-Western societies may display behavior that North Americans
would characterize as avoidant, but in reality these patterns are normative in othercultural groups (Marcus & Kitayama, 1991). Finally, attachment patterns, like
temperament, are not always stable over time and can change according to changes
in the infant’s temperament, home life, and environmental context.
Social referencing, another social-emotional milestone, also begins during
this period. Imagine a baby at this age falls down while playing with siblings
and the parent in the grass at the park. The infant has fallen on a relatively soft
surface and is not hurt. The infant appears surprised at the fall, but looks quickly
at the caregiver, who smiles and tells the infant, “Oops! You fell down.” The infant
smiles in return and continues to play. This interaction is indicative of socialreferencing, which occurs when the infant looks to either the primary caregiver orother important adults before reacting to ambiguous or novel situations. Anotherexample of this situation would be if an unfamiliar dog approached the infant,siblings, and caregiver while they were playing in the park. When the infant sees
his sibling and parent petting the dog and guiding the infant in interacting withthe dog, the infant will use these behavioral and emotional responses to appraise
the nature of the situation and respond accordingly. Although infants will be waryof strangers or new animals, they are more likely to respond positively if they view
their caregiver exhibiting positive emotions in response to the stranger’s or the
animal’s presence.

Social referencing
Social referencing is theterm used to describe
the way that infants taketheir cues from others indeciding what emotions andactions are appropriate in a
specific situation.

Social referencing can also give children opportunities to discover andimitate how to react to aspects of their social environment—in other words, socialreferencing provides a basis for acquiring knowledge about culture-bound social
nuances. For example, in a context where different castes co-exist, an infant froma lower caste may witness, and subsequently learn to imitate, submissiveness inNormal development

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IACAPAP Textbook of Child and Adolescent Mental Healththe presence of high-caste persons from watching interactions between primary
caregivers and high-caste individuals. Additionally, if this toddler grew up in
India, he might learn through social referencing at an early age to only use hisright hand for eating—in India, the right hand is the “clean” hand while the left
is the “dirty” hand, used for cleaning oneself after defecation. This prematureright-hand dominance might then lead the child to an earlier knowledge of left
and right compared to children his age in other countries, showing how socialreferencing can promote the learning of culture-bound social nuances and can leadto additional cultural differences.
Social referencing continues to develop throughout toddlerhood andbeyond, as individuals take cues from others to learn how to appropriately
respond to different emotionally stimulating situations or use others’ responses incomparison with their own emotional states and preferences. This milestone also
indicates that the infant is becoming aware of the difference between the self andothers, as well as of the desires and feelings of others. Corresponding with thisgrowing realization, another important milestone during this period is the infant’s
ability to follow simple directions given by others, which appears at nine to ten
months of age and continues to advance later in infancy. In this case, the infant
playing with the dog may be able to follow the mother’s command to give the dog
a stick to play with, and the infant will most likely be able to comply, following thedirections of the primary caregiver.
Age 13 months to 18 months
During this stage, more concrete signs of self-awareness develop. Infants now
are aware that their body, emotions and behaviors are separate entities from thoseof their primary caregiver and from others. Infants at this stage begin to recognize
themselves, a critically important step in development. A compelling example ofthis self-awareness is illustrated by an infant’s first look in the mirror. Althoughinitially surprised, most infants quickly learn that they are looking at themselvesand not someone else. Importantly, cross-cultural studies have shown that there
are significant differences in the responses of Western and non-Western infants
when looking at their reflection in a mirror (Broeschet al, 2010). While mirror
recognition may be a marker of growing self-concept in Western infants, this is
not necessarily the case for non-Western infants. As such, the consideration of themirror self-recognition as an index of self-awareness in children’s development is
influenced by the cultural context in which the child is embedded.
The changes during this period also show advances in emotional
development, as infants are now able to play with peers through imitation ormutual play tasks and can also demonstrate empathy towards others. Empathy is thecapacity to reflect and feel the emotions demonstrated by another person. Wheninfants see displays of emotion in their caregiver, particularly negative emotionality,
infants may show their own personal distress or comfort the caregiver, although
the latter empathic response typically occurs around the age of two. At this stage,
infants continue to differentiate their emotional experiences from others as theirsense of self-awareness grows, but also show signs of prosocial behavior.
Age 19 months to two years
As toddlerhood approaches, the infant becomes aware of the names forvarious emotional states and starts to use language and other behaviors to regulate

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IACAPAP Textbook of Child and Adolescent Mental Health

Table A.2.1 Summary of developmental milestones from zero to two years
Social-emotional and behavioral
milestones:
Attachment relationships

Cognitive and linguistic milestones:
Social stimulation and interaction

Birth to six months

•
•
•
•
•
•

•
•
•

•
•
•

19 months to two years•

Growing perceptual and sensory capabilities.
Improvement of memory and attention skills:
Dependent on the familiarity of the situation,
person, or infant’s motivation
Object permanence (eight months): Objects andpeople still exist although not seen or heard
Emergent language skills: Babbling wheninteracting with the caregiver, some will speak
their first word at 12 months or in the next stage
Can point to an object (e.g., a toy) around one
year
Will learn and respond to own name.

••

Expansion of their repertoire of earlier cognitive
skills:− Object permanence: Will look for the hidden
item in more than one location− Memory and retrieval: Increasing delays
between the observed behavior and its
imitation in other contexts− After the first word (eight-18 months):
Vocabulary grows to about 200 words.

•

Cognitive advances in memory, problem solving,
and attention:− Development and execution of action plans(e.g., building a structure)− Pretend or make-believe play (20 months)
and daily life play themes
Advanced linguistic skills:− Combining two or more words− Replacement of parts of a word with vowels
or consonants that are easier to say− Vocabulary growth.

13 months to 18
monthsSeven months to one year•

Better differentiation of external stimuli (sounds,
colors, etc.)
Recognition of facial expression
Preference for familiar people, stimuli and face-toface interactions.
Improvement of memory and attention skills(infants can remember and attend to certain
people, physical locations or objects)
Use of crying to express basic needs (hunger,
thirst, comfort, etc.)
Emergence of language precursors: Cooing (2months) and babbling (4 months)
Joint attention: Caregiver and baby take turns
exchanging facial expressions and noises.

•

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•
•
•

•
•

•
•

•

•

•
•
•
•
•
•

Early behavioral and emotional self-regulation
based on establishment of regular activities androutines (e.g., eating, sleeping, etc.)
Sleep cycles become more predictable by theage of eight weeks
Gaze aversion: Normal reaction to
overstimulation and arousal
Social smile: As a response to familiar humanfaces (6 weeks) and as initiated by the baby (3 or
4 months).
Multiple displays of emotions by age six months(e.g., frustration, anger, sadness, etc.)
Individual and contextual differences intemperament

Development of attachment relationships:
Infant’s bond with the primary caregiver
Separation anxiety: Displays anxiety when the
caregiver leaves
Social referencing:− How to react to ambiguous or novel
situations− Facilitates acquisition of culture-boundsocial nuances− Differentiation between self and others.

Self-awareness: Recognition of oneself
First demonstrations of empathy: Capacity toreflect and feel the emotions demonstrated byanother person (e.g., when infants see displaysof negative emotionality in their caregiver, they
may show their own personal distress or attempt
to comfort the caregiver).

Use of language and other behaviors to regulateemotional experience
Growing awareness of others
Emergence of more complex emotions (e.g.,
embarrassment, guilt, shame, etc.)
Lower intensity of separation anxiety
First signs of self-control: Able to delay
engagement in an enjoyable task
Play: Imitation of others, use of language andplay choices based on gender stereotypes.

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IACAPAP Textbook of Child and Adolescent Mental Healthhis or her emotional experience. For example, the infant may be able to name aninternal feeling state and tell the caregiver about it (“I’m mad!”) or offer the sadcaregiver a hug, showing an increasing capacity for empathy. Consistent with thegrowing awareness of others during these later stages of infancy, the more complex
emotions emerge at this time, such as embarrassment, guilt, and shame, all ofwhich are emotional responses to others’ perspectives of the child’s behavior. For
example, when one family’s two-year-old was caught with her hands in the cookie
jar, she appeared to respond with embarrassment to her mother’s scolding andstarted to cry when she realized that this action was not allowed. In earlier stages,
this same infant may have only cried out of surprise and anger when her mothertook the cookies.
Behaviors indicative of separation anxiety decrease in their intensity during
this stage and infants begin to show higher-level emotional regulation skills, suchas delay of gratification. Although self-control at this age varies according toindividual differences, some infants nearing toddlerhood can delay engaging in an
enjoyable task or wait to receive a prize if asked to do so. Play behaviors during thistime period revolve around imitation of other children, although language is also
introduced to describe or direct the play and infants begin to make choices aboutplay items based on gender stereotypes.
Infancy at a glance
The period of birth to two years is an exciting time of incredible
advances in cognitive, linguistic, social-emotional and behavioral development,summarized in Table A.2.1. During the first few months, the infant relies primarilyon the caregiver for the provision of basic needs and the facilitation of different
developmental advances across multiple domains, by age two the infant shows
signs of self-awareness, independence, social coordination, and empathy, which
continue to develop during toddlerhood and preschool, setting the groundworkfor social engagement and learning.

NORMAL DEVELOPMENT IN LATE TODDLERHOOD
AND PRESCHOOL:AGE TWO TO FIVE
Late toddlerhood generally refers to ages two to three. Preschool years
typically are between ages three and five. However, due to temporal overlaps withinthese developmental periods it is also reasonable to discuss cognitive, linguistic,social-emotional, and behavioral milestones throughout toddlerhood andpreschool ages as one developmental period spanning ages two to five. During thisstage, children continue to negotiate and balance their reliance upon the primary
caregiver with their desire for independence. They become more self-reliant in
preparation for the school-age years, often their first venture into the world beyond
their immediate family and community.
Cognitive and linguistic milestones
Cognitive milestones between ages two and five largely reflect thechild’s growing capacities in the areas of working memory, sustained attention,
problem-solving, and organization, which facilitate the child’s early learning andschool readiness. Piaget’s theory of cognitive development terms this period theNormal development

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IACAPAP Textbook of Child and Adolescent Mental Healthpreoperational stage, wherein the toddler makes advances in his capacity to represent
events or stories mentally, but remains egocentric, or self-focused, in his thinking(Piaget, 1954). However, recent research suggests a more flexible view of cognitive
development at this age, with the toddler and preschooler making some gains intheir abilities to empathize with or take the perspective of others.
A concerned parent of a three-year-old boy seeks the advice of a mental
health professional. The parent is worried because the toddler often talks at length
about an imaginary friend with whom the child says he plays many games. The boy
has named the imaginary friend, insists that the friend come everywhere with theparent and the rest of the family, and becomes upset when other family members
challenge the existence of this friend. While this behavior would not be considered
typical at the age of seven or eight, beginning in toddlerhood and preschool,normally developing children will engage in more complex sociodramatic play,including developing imaginary friends, reflecting a growing capacity for mental
representations.
Make-believe play with peers begins at age two or 2½, and increases incomplexity until age four or five, when preschoolers begin to mutually build upon
their make-believe play (Davies, 2004). Make-believe play indicates that children
are able to mentally represent their world both with and without play objects, andcan create imaginary sequences or representations of real or pretend life events. The
development of an imaginary friend is normal at this age and is only one of many
variants on sociodramatic play, which can also include playing house or doctor,
pretending to be a superhero, or pretending that stuffed toys or other items cantalk. Although at this stage children often pretend that inanimate objects can talk or
think, toddlers and preschoolers increasingly differentiate animate from inanimate
items. Sociodramatic play also involves and strengthens other cognitive and socialemotional capacities, such as working memory, attention, reasoning, self-control
and cooperation, and perspective-taking, all of which grow and develop during
this period.
At age three or four, toddlers also come to understand dual representation,or the recognition that a symbolic object, such as a photograph or model of a
train station, is both an object and a symbol of something else, such as a family
member or a train. Along with these advances in mental representation, children
during this period also transition from believing in magic and imaginary beings,
such as fairies, witches, vampires, or goblins at ages two and three, to searching for
logical explanations for make-believe persons such as Santa Claus at ages five or six.
However, magical thinking or belief in otherworldly figures will vary according tocultural beliefs and norms, and continued belief in these figures is not necessarily
atypical in certain cultural contexts. For example, in modern Chile, many
Mapuche communities believe witchcraft to be the primary cause of illness andmisfortune. Among the Mapuche, is not strange to find children, adolescents andadults who believe in the existence of witches and their magical powers. Therefore,
health practitioners working with these communities should take these beliefs into
account when conceptualizing normal development.
Whereas cognitive problem solving during infancy relied mostly on trial
and error, problem-solving during this stage is enhanced by the child’s greater
ability to sustain attention, engage in planning behaviors and use cognitive scripts

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IACAPAP Textbook of Child and Adolescent Mental HealthPhoto: San Jose Libraryor internal models of prior behavior and experiences for everyday problem-solving
or interpretive purposes. For example, a toddler may learn how to build a taller andmore stable structure with his blocks after learning how to do so from watchingpeers or caregivers and will integrate this learning into building larger block
structures in the future. In terms of interpreting everyday experiences, children
between the ages of two and five can typically relay the steps or actions involved in
activities such as visiting a relative (“we drive to grandma’s, she makes us dinner,
we watch a show, we go home”) or a day at preschool. Thinking at this stage also
becomes more oriented around cause and effect relationships, and memory spancan grow to up to four items. Problem solving can also occur through parental
scaffolding or support, and through the developing child’s use of private speech.
Private speech occurs when toddlers and preschoolers talk to themselves out loud,providing themselves with guidance when solving problems, such as thinking
through or planning their behavior (Berk, 2006). This milestone may also informthe development of more advanced memory, categorization and self-reflective
processes.
Cognitive and linguistic gains in school-based tasks become apparent
during these ages, when children learn early literacy and numeracy skills. Although
the learning of such skills will vary substantially according to language exposure in
the home, socioeconomic status and cultural context, many children during their
toddlerhood and preschool years learn to count and recite the alphabet. Children
also can usually relate details of a story to others and ask questions to clarify
their understanding by age five. Other language skills that continue to develop

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IACAPAP Textbook of Child and Adolescent Mental Healthand improve between the ages of two and five are in the areas of vocabulary andsentence construction. Important milestones include the growth of the child’s
vocabulary to about 2,000 words by age five, their ability to define known words
and integrate new words into sentences upon hearing them toward the end of thepreschool period. Two-year-olds will put sentences together with only two or threewords. By age four or five the child can typically communicate with sentences thatare more grammatically complex, utilizing different verb tenses, and can speak incoherent verbal exchanges with others.
Social-emotional and behavioral milestones
Many social-emotional changes occur during the toddler and preschool years.
While younger children may comply with parental demands or requests, children
at this stage are more likely to be resistant, as they balance their simultaneousdesires for parental scaffolding and increased autonomy. Toddler and preschoolertransition through a time of increased, and then decreased aggression and tempertantrums, and make overall gains in their understanding of emotions—in boththeir own emotional expression and that of others.
One afternoon, a mother comes to pick her child up from a relative’s homeand finds that her toddler bit one of her same-aged cousins in response to thecousin pushing the toddler while they were engaged in play. The mother is shocked,
embarrassed and wonders how this could happen—her daughter has never bitten
anyone at home and has been taught to use her words when she is upset. As her
family member asks the mother where the toddler learned this behavior, themother begins to feel concerned about whether this is age-appropriate or reflects
the beginning of a behavioral problem. This type of aggressive behavior is quite
normal for toddlers and even preschoolers. At age two, there is a universal increasein physically aggressive behavior, which can include biting, hitting of peers, family
members and the primary caregiver. Temper tantrums are also normative duringlate toddlerhood. These intense emotional outbursts usually originate with thechild’s resistance to parental requests, frustration with external events, or feelingstate of being tired or hungry. Temper tantrums typically appear between the agesof one and three, when children are still acquiring language skills to describe theiremotions and desires; they should decrease significantly, along with physicallyaggressive behavior, by ages four or five, when children increase their emotional
vocabulary, self-regulation skills and knowledge of socially appropriate displaysof emotion. Although behaviors like biting, hitting or temper tantrums can beembarrassing for parents—particularly when these behaviors happen in a public
setting like at preschool or in the supermarket—this behavior is normal for children
this age, within reason.

Researchers have recently
deconstructed the patterningof temper tantrums. Click on
the link to view (1:54)

While physically aggressive behavior decreases over the course of this period,
verbal aggression and other subtypes of aggression, such as instrumental aggression,
begin to increase. Whereas the aggressive behavior of most two-year-old children isreactive in nature (in response to an external event), as children age, their aggressive
behavior can become more instrumental, or calculated and goal-oriented, between
ages three and four (Berk, 2006). For example, four-year-olds may act aggressively
in order to gain access to a wanted toy, whereas the two-year-old in the previous
example bit her cousin in response to being pushed. On the other hand, children
also may become more competent social-problem solvers at this time, especially

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IACAPAP Textbook of Child and Adolescent Mental Healthgiven appropriate modeling by adults and other peers. Overall, aggressive behavior
is normative during this period, but should decline as children enter their schoolaged years, by about five or six years of age.
Other social-emotional milestones in emotional expression and inunderstanding the emotions of others occur during this period. In particular, more
complex behavioral and linguistic expressions of emotion, including empathy andsympathy, develop during this time. For example, when seeing his mother become
sad and upset one evening, a two-year-old might hug this distressed parent. In
contrast, an older preschooler will use physical actions as well as words to provide
comfort, asking, “What’s wrong mommy?” hugging his mother and even repeatingsoothing phrases he has heard from his mother or other caregivers, like “It will
be OK.” Over the course of this developmental period, children come to rely
more on words than behavior to express how they feel and to understand the
feelings of others. By age three or four, toddlers and preschoolers become moreaccurate in their appraisal of emotions and emotion-related behaviors in others,
including peers. This period is also when children develop their first friendships,
which increase in importance as children reach school age. An understandingof cultural norms for emotional expression, or emotional display rules, becomes
more engrained, and children become more aware of when to display certain
emotions. Part of the normative decrease in temper tantrums by the end of thisperiod is due to an increase in linguistic abilities, but a contributing factor is also
the preschooler’s recognition that these emotional displays are not appropriate
for most, if any, situation. Other display rules, such as when to show excitement
and when to laugh (playing games, after dad tells a joke) and when to be quiet(when mom is on the phone, at religious ceremonies or services) also become more
entrenched and understood. Both emotional display rules as well as moral beliefs,
which also begin to emerge at this time, are largely influenced by peers, caregivers
and the child’s larger cultural context.
Children’s capacity to describe mental states and the characteristics ofothers also grows in accordance with increasing self-awareness and language skills.
When a two- or three-year-old is asked to describe his best friend, this toddler
will use the friend’s name, but will rely on physical appearances, such as genderor age, or behavioral competencies to describe the friend. By contrast, children in
the later preschool years will describe others by labeling the emotions, attitudes
and characteristics of others. At this age, along with a description of physical traits
and gender, a child might describe his best friend as someone who is “funny, andgood at soccer, and comes over a lot.” During this period, children also come torecognize cultural and racial differences between groups. Finally, children reachthe milestone of gender constancy, or the idea that gender cannot be changed, andalso become more aware of gender stereotyped behavior by age five or six, adhering
more frequently to gender-based expectations of play and social behavior, which
may vary across cultures and environmental contexts. While a three-year-old
American toddler might enjoy playing house and dress-up with his female peers,
by age five this preschooler might choose to play with cars or other action-oriented
games with his male peers instead, adhering to gender stereotyped behavior that iscommon in North America. Gender constancy can also impact the way children
think about their future roles in the world of work, although this varies crossculturally. Consider a five-year-old North American boy who used to tell his

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IACAPAP Textbook of Child and Adolescent Mental Healthfather he wanted to be a teacher. One day, the child surprises his father tellinghim he doesn’t want to be a teacher anymore. When his father asks him about his
new resolution, he simply states, “I can’t—all teachers are women.” In contrast, a
Cameroon child of the same age might have a different experience, as in his school
there are only male teachers.
Certain behavioral changes that are related to physical maturation are
also important to acknowledge in the realm of behavioral development during
toddlerhood and preschool ages. Between the ages of two and five, children
become more competent at feeding themselves, while toileting oneself also typicallyemerges and becomes part of the child’s behavioral repertoire at this time, withthe majority of children reaching relative independence in this area by age four orfive. While puberty, or sexual maturation, does not begin until age 11 or 12, with
toddlers and preschoolers’ continuing growth in self-awareness, they may become
more curious about, and begin to explore themselves sexually. In the realm of
normative behavior, children at this age may touch themselves, ask caregivers or
peers questions about genitalia and show peers genitalia. While many parents areconcerned to see their child’s behavior becoming more sexualized, this behavior
is normative to some extent. However, forceful or sexually coercive behavior, andknowledge or imitation of adult sexual acts is usually atypical behavior and may
indicate instances of sexual abuse or overexposure. As with other developmental
milestones, physical and behavioral changes during this period should be consideredin the context of children’s individual and contextual differences.
Toddlerhood and preschool years at a glance
Toddlers and preschoolers show significant changes in their understandingof the self and others, evidenced by the completion of developmental milestonesin the areas of mental representations, problem solving, and other cognitive skills,
as well as in the areas of language, social-emotional process and behavior; thisis summarized in Table A.2.2. For many cultures, the successful completion of
toddler and preschool milestones indicates readiness for formal educational
learning or schooling, which usually begins at age six or seven.

Click on the picture
to view a short video(6:18) illustrating someof Piaget’s stages ofintellectual development.

NORMAL DEVELOPMENT IN CHILDHOOD:
AGE SIX TO 11 YEARS
Cross-culturally, the developmental periods from age six and to 11 is atime when children become more involved in the social world and learn skills
for later use in adulthood, through their transition to either formal schooling or
in societies without schooling, through apprenticeships related to future work or
familial roles. Children become more attuned to cultural norms, rules and laws,
and gradually begin to shift their focus and attention from parental relationships
to social and peer-oriented activities, particularly as they reach age 11 and the
beginning of adolescence.
Cognitive and linguistic milestones
Between the ages of six and 11, children make important information
processing advances in the areas of attention, automatization and memory, as wellas other mental operations. By about age seven, children are typically able to direct
their attention toward one set of stimuli or one task while simultaneously ignoring

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IACAPAP Textbook of Child and Adolescent Mental Health

Table A.2.2 Developmental milestones in late toddlerhood and preschool: Age two to
five years
Cognitive and linguistic milestones:
Mental representation•

Sociodramatic play (by age three):

−

•

•
•

•
•

•
•
•

Reflection of a growing capacity formental representations (imaginary
friends, etc.)− Involves and strengthens othercognitive and socio-emotional
capacities (e.g., working memory,
attention, reasoning, self-control,
cooperation, perspective-taking, etc.)
Dual representation (age three or four):The recognition that a symbolic object (aphotograph) is both an object and a symbolof something else (a family member)Continuously searches for logicalexplanations and cause/effect relationships(“why” period)
Cognitive scripts: Internal models of priorbehavior and experiences that guide child’s
behavior
Memory span grows up to four items
Private speech: Children talk tothemselves out loud, providing themselves
guidance when solving problems
Learning of early literacy and numeracy
skillsGrowth of child’s vocabulary to about 2,000
words by age five
Grammatically complex sentences by age
four or five (use of different verb tenses,
etc.)

Social-emotional and behavioral milestones:
Balance between parental demands and child’s
need of autonomy
•

•
•
•
•
•
•

•

•
•

Normative temper tantrums:− Appears between the ages of one and three,and decreases along with physically aggressive
behavior, by ages four or five
− Related to language and self-regulation skills
achievement
Decreased reactive aggression (in response to an
external event) and increased verbal and instrumental(goal-oriented) aggression
Aggressive behavior is normative during this period,
but should decline by about five or six years of age
More complex behavioral and linguistic expressions ofemotion (empathy and sympathy)
Development of first friendships.
Emergence of moral beliefs and motional display
rules: cultural norms for emotional expression
Growth of children’s capacity to describe mental states
and characteristics of others:− By age two or three, descriptions will rely on
physical attributes− By age four or five, the description will rely on theemotions, attitudes and characteristics
Gender constancy: Gender cannot be changed;
becomes more aware of gender-stereotyped behavior
at ages five or six
Physical maturation: Feeding and toileting oneself.
Sexual curiosity and self-exploration: Normative tosome extent.

extraneous stimuli. Whereas a five-year-old child has great difficulty focusing on
academic tasks while hearing other children talk or play outside the classroom
window, by age eight or nine most children can focus on their material, or are
easily redirected. This selective attention is necessary for critical thinking and thelearning of new skills or information (Berk, 2007). Self-control also plays a rolein the child’s attention skills, as do societal expectations, communicated throughschool or other learning environments.
A father tells his two children, ages six and 10, to get ready to leave thehouse quickly, as they are late for the 10-year-old’s soccer game. The father says,“Both of you please put on your shoes, go get your jackets, take a snack with you,and fill up your water bottles while I put the gear in the car”. When the father
comes back in the house, the 10-year-old is ready to go, but the six-year-old has
to be reminded of several steps by his father and older brother, such as getting his
snack and filling up his water bottle. “My six-year-old is really out of it,” thinks thefather, wondering whether his younger son has an attention or memory problem.

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IACAPAP Textbook of Child and Adolescent Mental Health

Although during this period of time, the child’s memory capacity and skills in bothstoring and retrieving information increases and improves, becoming faster andmore efficient, age 11 marks when the child is able to hold sequences of steps inmind and follow instructions more efficiently than in the early school years. In thisexample, the six-year-old has not developed the memory capacity and efficiency
that his older brother has. During these years, the child can also rely on gist-based
memory, or the basic components of what they learned or what happened (Berk,
2007). While the six-year-old may remember some parts of his brother’s game,his older brother will likely come home with a more comprehensive memory; yetboth children will remember the overall “gist” of what happened—that the older
brother’s team won the game.
Children also become aware of various skills to improve or increase memory
during this period, spontaneously beginning to use cognitive rehearsal strategies
like the creation of mental cues and categories, or the repeating of information
to help themselves recall important tasks or processes. When he first learned therules of soccer at age eight, the older child in our example often repeated several
rules to himself during practice or after being reminded of them by his coach as amethod to improve his memory. Soon, the knowledge of these rules became more
automatic, as memory is involved in the process of automatization. Automatization,or automaticity, refers to the act of practicing or repeating new information andrelated thoughts or behaviors until these processes become more routine (Davies,
2004). Automaticity is a necessary component in learning virtually any new task
or skill, such as academic tasks like reading, writing, completing mathematics
operations, or other skills like learning to play soccer.
Along with gains in information processing, children between the ages of
six and 11 meet many milestones in several different cognitive operations. During
the preschool years, asking a child to differentiate their right and left will leave
most children confused and the vast majority will not understand when a parent
tells them that they have to “wait five minutes” before having a snack. Preschoolers
have a limited orientation to time and spatial organization while, beginning atage six, children become more advanced in these areas. By this age a child candistinguish their own right from left and can note the right or left side of othersaround age seven or eight. Time and calendar dates become more meaningful
after age seven, when most children can usually identify when their birthday is,
and will understand when they are told to “wait five minutes” for a snack. Other
mental operations include more sophistication in the seriation and categorizationof objects according to specific characteristics such as shape, size, length, color, as
well as increasing capacity for the processing of auditory and visual information.
It is important to note than not all children classify objects in the same way acrosscultures. Children in many communities, especially if they have not had muchschooling, might sort objects according to their function rather than according toother dimensions such as size, shape, or color. For example, children with moreexperience working on a family farm may classify a hoe and a potato in the samegroup because a hoe is used to dig a potato.

Seriation
Refers to the ability ofsorting objects or situations
according to characteristics
such as size, color, shape,or type. This capacity
is developed during theconcrete operations stage,
usually from seven to 12
years of age.

Problem solving and reasoning also improve during childhood as thinking
becomes more organized, creative and flexible, and the capacity for metacognition,
or “thinking about thinking” develops. As a related process, cognitive self-regulation,or the process of monitoring one’s thoughts and actions in learning new skills

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IACAPAP Textbook of Child and Adolescent Mental Healthor solving problems, also occurs during this period and continues to develop
during adolescence to inform more abstract problem-solving. Finally, emerging
literacy and numeracy skills at age six and seven evolve and become increasingly
sophisticated as the child engages in school-based academic tasks, with the childmoving from learning to read in the early elementary years to using reading skills
to learn new information by the end of middle childhood, at age 11.
As in other periods, cognitive development influences the degree of thechild’s language capacity. For example, as children make gains in their information
processing skills, particularly in the areas of selective attention and memory, they
are better able to learn new words, integrate these words in sentences, and adhere
to grammatical structures they have learned in school or conversationally. An
important linguistic milestone between the ages of six through 11 is vocabulary
growth, which typically increases to an average of 10,000 words during this period.
By age nine to 11, children can also understand the double meaning of somewords, such as when words are used metaphorically. For example, when given a
sticker at school for good behavior that says “You are a shining star!” a child during
this stage will understand that they have done a good job and are being comparedto the brilliance of a star.
When one child’s grandparents used to call him during his toddlerhood andpreschool years, the child would stare into the telephone, saying a few words attimes and talking somewhat reluctantly into the speaker. Around age six, this childappeared more comfortable using the phone and began to speak even more clearlyon the phone between the ages of seven and eight. Children also make important
advances in their conversational skills at this time, acquiring shading skills, orcommunication skills related to gradually changing the topic of the conversation(Berk, 2007). Whereas conversations with his grandparents used to involve thechild answering a series of questions, during the stage from age six to 11, this childbegan to spontaneously offer his grandparents new information and ask questionsof them that were relevant to their conversation. However, the extent of the child’s
vocabulary growth and other linguistic skills during this period will depend on
cognitive abilities and will additionally vary by cultural context and societal norms.
Social-emotional and behavioral milestones
Childhood is also a time to develop mastery of self and others, including
self-esteem, emotional regulation, perspective taking, moral development, andpeer relationships. As children begin to compare themselves to others and receive
feedback from teachers or other adults, self-esteem, or beliefs about self-worth,
begins to drop in comparison to its higher levels during the toddler and preschool
years. One day after coming home from school, a 10-year-old girl remarked to hermother, “I’m not good at dance anymore…so I’m not gonna go to class today.”This surprised the mother, as typically her daughter loved her afternoon danceclass and always wanted to practice her routines in front of others. After somequestioning about this statement, her daughter said that she saw another groupof girls practicing a popular dance at recess and felt she wasn’t as good as thosegirls based on what she saw, and based on how positively her peers reacted to thisdisplay. This 10-year-old’s self-esteem was modified through her interactions in thesocial world, which holds more weight than in previous years.

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IACAPAP Textbook of Child and Adolescent Mental HealthSelf-esteem during this period is increasingly based on the child’s selfperceived competence or peer group status, or through identification with primary
caregivers, teachers, and other youth (Schaffer & Kip, 2010). Cultural factors andgender differences influence both the development of self-esteem and the degree
to which children make social comparisons to others. For example, children from
Asian cultures have been found to have lower self-esteem despite higher masteryof various academic tasks. Girls in North America have also demonstrated lower
levels of self-esteem during this period compared to boys.
The need for self-control increases during this developmental stage aschildren engage in purposeful actions that are often in larger groups (such as formal
schooling). This engagement requires two important self-control skills: delay ofgratification and impulse control. Whereas a very young child wants immediate
gratification, between the ages of six and 11, children learn to wait for a reward,
engage in activities other than play, and conform behavior to the norms of the peergroup and context. In part this is facilitated by watching peers use self-control.
Self-control also varies by temperament—some children are better able to control
desires and impulses than others regardless of what peers do or specific reward
structures.
Children between the ages of six and 11 are even more aware of genderstereotypes and roles than in previous developmental periods. Exploration ofgender roles occurs during this period, with youth increasingly identifying withsame-sex role models, whether peers, caregivers, relatives, teachers, or celebrities.
This developing sense of gender identity can also impact self-concept and facilitate
gender socialization. Although girls and boys can certainly have cross-genderfriendships between the ages of six and 11, a look around an elementary schoolrecess yard will show that groups of children are generally gender-segregated,

Sri Lankan children playing ina beach(Photo: Dhammika Heenpella)

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IACAPAP Textbook of Child and Adolescent Mental Healthwith girls and boys separately playing or talking together in same-gender groups.
Groups of girls may stand around and socialize more frequently than engaging in agame of sports or tag, for example, while at recess, which is what many boys preferto do while on a break during their school day. Such gender segregation has been
consistently found across cultures as well.
Emotional development and regulation continues during middle
childhood, both of which are facilitated by simultaneous advances in cognitiveand linguistic domains. Beginning at age eight, children start to realize theycan experience more than one emotion at once, and also become more adept at
appraising the range and combinations of emotions in others. Although children
become aware of emotions such as pride, shame, guilt, and embarrassment during
the preschool years, awareness of these more complex emotions becomes moresophisticated and children change their behavioral responses to such emotions as
they develop in their maturity. When a three-year-old doesn’t get to play with acertain toy she wants, she may scream and cry out of frustration. Her mother may
realize that the three-year-old is not only upset but is also over-tired and needs totake a nap. An 11-year-old in middle childhood may become similarly upset when
she doesn’t get to stay up as late as older siblings to watch a television program,but may have a better understanding that she is also tired and has to get up earlyfor school the next day. The 11-year-old will not typically scream and cry because
she isn’t getting what she wants and may be able to go to bed after some discussion
about this instead of arguing with her parents (although in adolescence, arguingwith caregivers may be a more probable outcome).
During this period, children also learn to regulate and manage their emotions
and behavioral responses through two types of adaptive coping strategies, whichmost children use by about age 10. Although it is unlikely that the 11-year-old
in the example above will need to employ coping strategies to regulate her upset
about not staying up late, this same child will likely draw upon coping skills when
she finds out that she hasn’t been invited to the birthday party of a popular girlat school. Problem-focused coping occurs when children identify if the issue they
are facing is changeable or not, think about possible solutions, and then carry out
their chosen solution. The 11-year-old in this case thinks about asking if she canattend the party anyway, or contemplates telling a friend who was invited to ask
the birthday girl why the 11-year-old didn’t receive an invitation. However, these
options don’t feel comfortable to the 11-year-old. When this type of problemfocused coping strategy does not work or is not applicable, children typicallyengage in emotion-centered coping, which involves the child working to manage
or control distressing responses through different strategies, such as seeking social
support when problems cannot be immediately solved. The 11-year-old decides totalk to another friend about the party and tell the friend how she feels; their talkabout this over the phone makes the 11-year-old feel better about not receiving an
invitation to the party.
Empathy is another complex emotional state that continues to develop
during this period. Children become more sophisticated in their ability to think
about the thoughts or emotions of others, showing increased perspective taking
that also informs their capacity to demonstrate empathy. They can simultaneously
think about their own thoughts and feelings at the same time as they appraise andempathize with the thoughts and feelings of others and, by age 10, they start toNormal development

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IACAPAP Textbook of Child and Adolescent Mental Healthrecognize the views of an impartial third party as well. In the example above, whenthe 11-year-old girl calls her friend to seek support due to her being excluded froma birthday party, the friend she calls is able to empathize with her friend’s distress,
examine her own feelings about the party and discuss what the birthday girl islikely to be thinking and feeling by not inviting everyone to the party.
Moral development during this period is also related to the development ofchildren’s empathy, in that youth are increasingly able to integrate the perspectivesof others into their worldview and sense of morality. Children’s moral views, or senseof “wrong” versus “right,” during this stage are typically rule-governed, reflecting aheightened awareness of societal or cultural norms, laws, and customs. However,children’s moral development is also dependent upon immediate environmental
contexts and interactions they see in their families and neighborhood, even if thesediffer or are deviant in comparison to larger societal/cultural laws and customs.
Normative beliefs, or the child’s beliefs about the bounds of appropriate behavior,
can vary substantially based on children’s exposure to aggressive or deviant
behavior, with the development of normative beliefs in early childhood predicting
the extent of youths’ aggressive behavior during later childhood (Huesmann &Guerra, 1997).
An increased focus on rules and laws also impacts on children’s peer
relationships and chosen play activities between the ages of six and 11. During thisperiod, children form friendships on the basis of trust in one another, kindness,
support and a mutual enjoyment of similar hobbies or activities. Many children
become involved in rule-oriented games, such as sports or activities that require
planning or strategy, and children sort themselves into various peer groups during
free play activities. Children at this age who behave in a prosocial and nonaggressive manner are usually more popular or socially accepted than those whoare either aggressive or socially withdrawn and awkward.
Peer victimization or bullying also begins to occur more frequently during
this period. Typically, bullies are socially rejected, aggressive children who physicallyor verbally target and attack victims who are less assertive, physically weaker, andusually socially withdrawn, or those who exhibit marked differences from peersin their physical or other characteristics. Categories of bullies and victims are notmutually exclusive as many victims can bully others and vice versa, resulting in abully-victim category of youth who engage in both of these behaviors (Cook et al,2010). For example, one eight-year-old boy is constantly pushing another sameaged peer around on the playground. This eight-year-old is taller and stronger
than the smaller eight-year-old that he pushes around, often allowing the bullying
eight-year-old to take the weaker child’s money for lunch. Most of the other kids
at school don’t socialize with the eight-year-old bully, as he seems angry most of
the time, and his behavior causes him to get in trouble frequently with the school
principal. After he leaves school, the eight-year-old usually walks home throughthe same couple of neighborhood streets, and is almost always confronted by abigger and stronger 11-year-old, who pushes the eight-year-old to the groundnearly every day, asking him for his lunch money. In this case, the eight-year-old
who bullies on the playground is also a victim of bullying by an older child.
As children continue to physically mature, sexual curiosity and selfexploration also continues, within the bounds of age-appropriate behavior, as

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IACAPAP Textbook of Child and Adolescent Mental Health

Table A.2.3

Developmental milestones in childhood: Age six to 11 years

Cognitive and linguistic milestones:
Gains in information processing
•
•

•
•

•

•
•

•
•
•
•

Better self-control and use of divided,
focused, and selective attention
Gist-based memory: Basic componentsof what was learned or what happened
Better use of skills to improve or increase
memory, and automatization
Time and spatial orientation andorganization: Differentiation of right fromleft
Seriation and categorization of objects
Increasing capacity for processing
auditory and visual information
Development of metacognition, or“thinking about thinking,” and cognitive
self-regulation, the process ofmonitoring one’s thoughts and actions.
Emergency of more sophisticated literacy
and numeric skills
Vocabulary growth: Up to 10,000 words
Understanding the double meaning ofwords and metaphors
Advances in conversational skills:
Acquirement of shading skills, related
to gradually changing the topic of theconversation

Social-emotional and behavioral milestones:
Development of self and others mastery
•

•

•

•

•
•
•
•

Self-esteem or beliefs about self-worth:− Diminution as a result of interpersonal comparison.
− Based on perceived competence or peer group
status, or identification with significant adults.
− Influenced by cultural factors and genderdifferences.
Better self-control:− Related to delay of gratification and impulse control.
− Facilitated by watching peers use self-control.
− Influenced by child temperament.
Greater awareness of gender stereotypes and roles:− Developing sense of gender identity can impact
self-concept and facilitate gender socialization.
− Social groups are generally gender-segregated.
Increasing emotional development, regulation, andcoping:− Problem-focused coping: Based on trying to solve
the problem.
− Emotion-centered coping: Based on trying tomanage or control distressing responses.
Progress in empathy and moral development: Due toincreases in children’s perspective taking abilities.
Friendships based on the trust in one another, kindness,
support and mutual enjoyment of similar hobbies or
activities.
Peer victimization begins to occur.
Sexual and/or romantic interests may begin to develop at
this stage.

described above in the toddlerhood and preschool years’ section. Although males
and females at this age typically sort themselves into same-sex peer groups, sexualor romantic interests may begin to develop at this stage, although these interests
become more overt with the onset of puberty, in adolescence.
Childhood at a glance
As children develop, between the ages of six and 11, they negotiate critical
milestones related to their entrance into the social world, summarized in Table
A.2.3. Between these ages, children work to develop a sense of mastery overacademic and social domains and become more interested in and involved in theirpeer group. By the end of this period, the cognitive, linguistic, social-emotional,
and behavioral changes youth have made prepare them for their transition toadolescence and their development of personal identity during this period.

NORMAL DEVELOPMENT IN ADOLESCENCE:
AGE 12 TO 18 YEARS
Adolescence has long been thought of as a time of change across multiple
domains, particularly in the physical and social-emotional realms. With pubertal

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IACAPAP Textbook of Child and Adolescent Mental Healthchanges beginning for most children at age 11, hormonal changes impact youths’
functioning and negotiation of developmental milestones in the areas of cognitionand language, as well as in their social-emotional skills and behavior. Adolescencealso marks a shift from a relatively equal focus on both caregivers and peers, toincreased attention on the peer group. Adolescence also is a period when youth may
increase in their risk-taking behavior and experimentation (Guerra & Bradshaw,2008), and become more susceptible to peer influences. Overall, adolescence is aperiod that prepares youth for the transition into adulthood and the formulationof their adult identity (Erikson, 1968).
Cognitive and linguistic milestones
Cognitive milestones between the ages of 12 and 18 can be characterized
by the adolescent’s growing self-consciousness and metacognition, or increased
attention to and awareness of their own thought processes. During this time,adolescents are increasingly self-focused and may also improve in their cognitive
self-regulation strategies. However, due to the hormonal changes that come withthe onset of puberty, despite their greater sophistication in complex reasoning andformal mental operations, adolescents may also become more impulsive and lessattentive at times, and may also struggle to effectively make decisions and plan forthe consequences of their behavior.
Cognitive distortions about the self also appear with adolescents’ increased
self-consciousness—called the imaginary audience and defined as a belief that they
are the main focus of other people’s attention (Berk, 2006). Consider this example.
Before leaving the house for a family holiday party, a mother tells her 13-year-old
son and 15-year-old daughter that they have to wear some of their nicest clothes,and suggests her daughter wear a new long dress and her son wear the sweater his
grandmother gave him. When the family is ready to leave, the 15-year-old comes
downstairs wearing a short dress and lots of makeup, which her mother asks her
to remove. The 15-year-old becomes immediately upset, arguing with her motherand exclaiming that the long dress is “babyish” and that “everyone will notice that
I’m not allowed to wear makeup!” Shaking her head, the mother instructs herdaughter to go back upstairs, take off her makeup and change into the longer dress.
When her 13-year-old son comes down, she is equally surprised to see he isn’t
wearing the sweater and wants to wear his basketball jersey instead. Her son tells
her that, “all of the other cousins get to wear their jerseys and all of them will see
this dumb sweater and make fun of me!” The mother wonders how her children
became so self-involved; her kids never acted like this when they were younger.

Click on the picture
to view a short video(12:02) on developmental
theorist Eric Erikson’s
stages of psychosocial
development.

Another common cognitive distortion of this period is the personal fable, aresult of the imaginary audience. Thinking of themselves as the center of attention,
adolescents come to believe that to be the case because they are special and unique.
Thanks to this personal fable, young adolescents also believe that their feelings andemotions are different, often more intense and terrible, than those of others. It isquite common for an upset teenager to exclaim to family members that they will
“never understand” how the teenager feels. The personal fable may also give rise toa sense of invulnerability and singularity, creating a propensity for behavioral risktaking. For example, a 15-year-old adolescent who is experimenting with drugs
and alcohol might think, “other people will get hooked on drugs but not me,” ora 16-year-old girl who is engaging in high risk sexual practices can think “other

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IACAPAP Textbook of Child and Adolescent Mental Healthwomen will get pregnant or get infected with HIV, but that stuff would never
happen to me.”
Despite these cognitive distortions and difficulties with rational decisionmaking and impulsivity, teenagers become more advanced in their performanceof mental operations and their information-processing skills and cognitive selfregulation improve overall. Important cognitive milestones in this regard include
greater planning and problem-solving abilities, abstract thinking and reasoning,
and the capacity to understand, compare, or integrate advanced theoreticalperspectives.
The majority of linguistic advances in adolescence are a continuation ofprevious milestones, such as vocabulary growth in middle childhood, and therefinement of grammatical structures. The adolescent’s vocabulary can grow toover 40,000 words by age 18, and will likely include a number of abstract terms,
with adolescents mastering the syllable stress and intonation of these more difficult
words (Berk, 2006). With their improvements in vocabulary and grammaticalskills, by age 18 adolescents can typically read and understand adult literature.
Finally, adolescents evidence skill improvement in the area of pragmatics. By age
14, adolescents will use and understand conversational nuances, such as sarcasm
or irony, and by age 18, their communication patterns are increasingly patterned
according to specific contextual cues or societal expectations across a variety ofenvironmental situations.
Social-emotional and behavioral milestones
Adolescents are more self-aware and self-conscious than younger children
and may engage in more frequent risk-taking or experimentation behaviors (Guerra& Bradshaw, 2008), particularly when encouraged to do so by peers. Socialemotional and behavioral development during this period are characterized by astruggle to assert one’s own identity and autonomy, although often in a context
that maintains dependence on caregivers for basic needs (food, clothing, finances,transportation). Over the course of adolescence, youth negotiate many milestones
related to social-emotional and behavioral development, all in preparation for thetransition to adulthood.
With greater self-awareness and self-discovery in adolescence comesmarked fluctuation in the adolescent’s self-esteem, emotional regulation, andoverall identity formulation. Adolescents have increased self-esteem or an inflatedsense of self-importance and uniqueness at times, but also tend to experience more
frequent self-criticism, sadness and anger. The intensity of such high and low
emotional experiences is linked to adolescents’ hormonal changes during puberty,
to their growth in metacognition and to the increase in the dimensionality of selfesteem, which now includes academic or work performance, social competencies,
peer relationships and romantic relationships and appeal.
Mild to moderate variations in mood and behavior are normal and to be
expected. A teenager may come home one day in a good mood after doing well ona test, act cheerfully and talk with his mom about his day. Two days later, the verysame teenager may be irritable, ignore his family and refuse to talk to his mother atall, only to be very pleasant at dinner, leaving his mother completely confused. It
may be that he had a fight with a girlfriend, who called to apologize before dinner,or any number of momentary disappointments.

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IACAPAP Textbook of Child and Adolescent Mental Health

The desire to fit in orconform to the standards of
one’s clique or peer group
becomes more marked
during early adolescence.

Unfortunately, this type of moodiness is common among adolescents, which
can lead to frequent disagreements with others, most often primary caregivers.
Disagreements with parents typically increase between the ages of 12 and 14,
but by age 18 adolescents usually exhibit less moodiness and engage in fewer
disagreements with caregivers, on average.
In terms of peer relationships, youth tend to sort themselves into selective
groups or cliques between the ages of 12 and 18, with each clique exhibiting
different group norms, attitudes and value systems. The importance of peer groupconformity also emerges during early adolescence. The desire to fit in or conform to
the standards of one’s clique or peer group is more apparent in younger adolescents
between the ages of 12 and 14, as these youth tend to look to the peer groupfor direction in their dress, choice of recreational activities and taste in various
media (movies, TV, music), all of which are shorter-term behaviors and featuresof identity. One father is confused by his 14-year-old daughter’s new tastes andclothing style; all of a sudden she dresses in all black, exactly like two of her peers,
and asks repeatedly whether she can dye her hair purple. The music coming fromher room sounds different than it used to and the father notices that his daughter
has started to paint her nails black as well. When asked about her new taste inclothes and music, the daughter appears annoyed and tells her dad that she’s
becoming her “own person”. Her father teases that she looks like a carbon copy ofher friends and the 14-year-old becomes even more upset, telling her dad that hejust doesn’t understand her and that she is more “alternative” than any of her peers.
Six months later, the 14-year-old visits her older cousin and comes backwearing a new flower-print top, brightly colored jewelry, and pink nail polish.
“What happened to all the black?” her father asks. The 14-year-old rolls her eyes,
tells her father that “black is so over” and continues in her new style of dress forthe rest of the year, which her friends soon conform to as well. However, by theage of 18, the father notices that his daughter’s “style” and tastes have solidified

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IACAPAP Textbook of Child and Adolescent Mental Healthand fluctuate much less than earlier in adolescence. At 18, when his daughter looks
back at pictures of herself in all black, she laughs and says she remembers how
important it was for her to dress exactly like her friends or her older cousin.
Such peer influences, like taste in clothing or music, usually do not conflictwith the adolescent’s preexisting moral beliefs and attitudes, although some peergroup norms may be more deviant than others. For example, aggressive youth
may sort themselves into antisocial peer groups that are involved in delinquent
behavior. Some adolescents may join a formal street gang, or may just hang out
with other peers who enjoy similar antisocial behaviors, such as “tagging” or putting
graffiti on public buildings, drinking alcohol or using drugs. These antisocial peergroups can also influence less aggressive youth that join such groups in a process
called deviancy training, in which aggressive or delinquent peers mutually “train”
or socially reinforce the development of antisocial behavior in one another or inless aggressive youth with whom they associate (Dishion et al, 1996; Poulin et al,1999). For example, a less deviant adolescent who occasionally associates witha group of more antisocial peers, may receive social praise, physical protection
from other aggressive youth, or invitations to exclusive parties after he steals his
parents’ alcohol to bring to his peers, all of which reinforce his developing problem
behavior. Peer pressure to conform to peer group norms or behaviors also influencesadolescents’ involvement in both prosocial and antisocial behavior, dependingon the nature of the peer group, although peer pressure and influence decrease
somewhat in strength by age 18, when personal identity and moral beliefs become
more solidified (but not yet stable).
Deficits in adolescents’ rational decision-making skills and increases
in impulsivity during this time can lead to greater experimentation in general
problem behaviors, such as cutting school or persistent truancy, drug and alcohol
use and abuse, sexual-risk taking, and acts of violence or aggression (Guerra &Bradshaw, 2008), especially when taking part in such behaviors is sanctioned by
the adolescent’s peer group. In the example above, the adolescent is more likely tosteal alcohol from his parents to give to his friends because his peer group often
drinks together. For this reason, many prevention programs occur in middle andhigh schools to address this universal increase in problem behavior. However,involvement in problem behaviors will depend a great deal on the adolescent’s
individual and group-based social and environmental differences. Bullying also
continues during adolescence, although it is less physical in nature when compared
to bullying in middle childhood.
A 15-year-old girl sits at her computer and starts to cry quietly, shaking
her head at the screen and trying to close her web browser quickly before her older,
20-year-old sister walks over to see what is going on. The 15-year-old looks down,
appears embarrassed, and finally admits that a boy she had liked posted a pictureof her on a social networking site that he had taken on their first date together.
Although the picture was not sexually explicit, he wrote some suggestive comments
under the photo that insinuated that they had “gone all the way” together, which
was not true. Another girl in the 15-year-old’s peer group had commented on thepost and called the 15-year-old some derogatory names, leading others to do thesame, all based on the rumor that the boy’s social networking post had started.
This type of event is indicative of the peer victimization that can take place duringadolescence: it may become sexualized in nature, may occur indirectly and is more

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IACAPAP Textbook of Child and Adolescent Mental Healthlikely to take place while teens use the internet (called cyberbullying; Williams &Guerra, 2007).
Victimization in adolescence may also be more social or relationally focusedin content, reflecting relational or verbal as opposed to physical aggression. Further,whereas deviant or aggressive peers were once rejected in childhood, these youth
can sometimes become popular in adolescence. For example, the above situationin which an adolescent steals alcohol from his parents could lead to increased
respect from others in his peer group and could increase his popularity at school.
However, popular adolescents typically continue to reject highly antisocial youth,and friendship quality between youth usually depends on prosocial characteristics,
like mutual trust, loyalty and support. If the adolescent stealing alcohol had also
forced another adolescent to drink the alcohol until he or she passed out, the larger
and more popular peer group would likely reject this adolescent and his moredeviant behavior.
As adolescents work to develop their identity, they may reach a greater
understanding of their own moral beliefs, and continue to improve in theirperspective-taking abilities. Adolescents will also behave more in accordance with
their personal value system over time, which can include religious, cultural, andother influences apart from those of the peer group, particularly as they near age 18.
However, social-emotional and behavioral development does not conclude withadolescence and continues to inform identity development in early adulthood.

Table A.2.4

Developmental milestones in adolescence: Age 12 to 18 years

Cognitive and linguistic milestones:Complex reasoning and formal
mental operations
•
•
•
•
•
•
•

Improvement of information-processing
skills, metacognition, and cognitive selfregulation strategies
Growth in self-consciousness andcognitive distortions
Imaginary audience: Belief that they are
the main focus of other people’s attention
Personal fable: Belief that one’s
experiences and feelings are unique fromothersDifficulty with rational decision-making
and impulsivity
Vocabulary growth (over 40.000 words by
age 18) and refinement of grammaticalstructures
Progress in conversational skills.

Social-emotional and behavioral milestones:
Assertion of one’s identity and autonomy
•
•
•

•

•
•
•
•
•

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Frequent and intense fluctuation in self-esteem and emotional
experiences linked to hormonal changes
Self-esteem increases in dimensionality: Academic or work
performance, social competencies and peer relationships,
romantic relationships and/or appeal, etc.
Mild to moderate variations in mood and behavior:− Normal and to be expected− Can lead to frequent disagreements with others, especiallyprimary caregivers
Importance of peer group conformity:− Adaptation to the group norms, attitudes, and value systems− Possible processes of deviancy training and peer pressure
More likely to participate in risk behaviors: drug and alcohol use
and abuse, acts of violence and aggression, bullying behavior,
etc.
Peer victimization becomes more social or relationally focused incontent
Friendship quality depends on prosocial characteristics such as
mutual trust, loyalty, and support
Greater understanding of their own moral beliefs
Improvement in their perspective-taking abilities.

36

IACAPAP Textbook of Child and Adolescent Mental HealthIn many traditional societies, the transition from childhood or adolesence
to adhulthood is usually accompanied by culture-specific rituals. Although there
is great variation across cultures, there is a tendency to mark children’s rupture
with their previous life through various rites of passage or shifts in the individual’ssocial behavior, which demarcate the beginning of adulthood. For example,
within the Kurnai community in Australia, a boy’s relationship with his motherchanges considerably from the moment he is recognized as a man, as he has togive up his childhood games and take on different responsibilities. Also common
to Aboriginal Australian communities is the rite of passage called a “walkabout,”
in which adolescent males separate from their tribe and live in the wilderness fora period of time, marking the transition to adulthood, among other shifts at thistime.
Similarly, in modern societies one may find activities that resemble theserites of passage, although modern rites of passage may be markedly different innature. For example, the numerous exams and the multiple admission tests thatmany adolescents have to endure in order to gain entrance to college or graduate
school may constitute an initiation into adult society. In the same way, for some
cultures it is common to celebrate such academic achievements through graduation
parties after the adolescent completes different stages of his or her studies (such as
high school). Religious ceremonies, such as the Bar or Bat Mitzah in Judaism, or
the Confirmation in Catholicism, may also mark the passage from chilhood toadulthood. In Hispanic/Latino communities, the “Quinceañera,” a celebration atage 15 that represents the entry of young girls into adulthood, is when girls gain
certain social privileges, such as going to dances, watching more adult movies,
using makeup, and having a significant other. These rites of passage and markersof the transition from adolescence to adulthood vary substantially both across andwithin various cultures and racial/ethnic groups. Practitioners and other healthcare
providers should be aware of the culture and context in which their clients areembedded and should practice cultural sensitivity, both when examining adolescenttransitions to adulthood and when considering the previous developmental stages.

Other useful Internet
resources••

Adolescence at a glance
Normal adolescent development across cognitive, linguistic, socialemotional, and behaviors domains reflects the child’s increased involvement in
the social world, growing sense of identity, and preparation for the transition toadulthood. Common patterns in adolescent development include the developmentof higher-order cognitive and linguistic skills, an initial increase in moodiness,caregiver-child conflict, and conformity with group norms, with a decreasein these behaviors by age 18. Although identity and social roles do not solidify
during this stage, the milestones that occur in adolescence greatly inform later
adult functioning across multiple developmental domains.

•

CONCLUSIONS•

It is important to understand the timing and progression of normal
developmental milestones throughout the periods of infancy, childhood andadolescence, and within cognitive, linguistic, social-emotional and behavioral
domains. Normal development is defined as not only the absence of psychopathology,
but also the negotiation of important milestones in a timely fashion. However,the definition of “normal” development must always be contextualized according

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•
•

•
•

Centers for Disease
Control andPrevention
University ofMichigan Health
System (with videos
and information in
Spanish)Child & Family
Webguide – Tufts
University
Child Developmental
Institute
Palo Alto Medical
Foundation(information available
in English andSpanish)Medline Plus: Trusted
Health Information
for You
National Institute
Of Child Health andHuman Development
Center of theDeveloping Child37

IACAPAP Textbook of Child and Adolescent Mental Healthto the myriad of racial, ethnic, cultural and environmental differences thatexist both within and across different groups of youth. For mental healthprofessionals, this review of normal development can assist in history-taking andassessment, treatment planning and the appropriate choice of evidence-based anddevelopmentally appropriate interventions. Although deviations from average oron-time development are not specifically discussed in this chapter, other chapters inthis volume provide thorough information about the presentation of and evidencebased treatments for various physical and mental health disorders that occur inyouth. The applied professional is encouraged to use the following discussions ofatypical behavior as well as this chapter’s review of normal development to informfuture conceptualizations of youths’ functioning during infancy, childhood andadolescence.

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