DOI: 10.7546/PIBL.XXXIV.21.10

Б Ъ Л ГА Р С К А А К А Д Е М И Я Н А Н А У К И Т ЕИЗВЕСТИЯ НА ИНСТИТУТА ЗА БЪЛГАРСКИ ЕЗИК „ПРОФ. ЛЮБОМИР АНДРЕЙЧИН“К н и г а ХХХIVLANGUAGE DEVELOPMENT IN TYPICALLY DEVELOPING
CHILDREN AND CHILDREN WITH DEVELOPMENTAL
DEFICITS: A CONCISE QUALITATIVE REVIEW
Mila Vulchanova, Valentin Vulchanov

Language Acquisition and Language Processing Lab
Norwegian University of Science & Technology – Norway
Abstract:
The current review provides a concise qualitative overview of how language develops in
typically developing children in comparison to developmental deficits which adversely affectlanguage, with a focus on language impairment (Developmental Language Disorder) andautism spectrum disorder (ASD). The review traces the main stages in language acquisitionand observed trajectories in typical children and children with developmental deficits. The
main factors which impact on language development are highlighted and seen in the context
of language outcomes. The review covers research across languages and cultures, and acrosspopulations of speakers.
Keywords: language development, typically developing children, developmental
deficits, language competence, developmental trajectories, factors in language development

1. Typical language development
1.1. Typical language development and developmental deficits
Language development is a long process characterized by dynamic changes
in children’s communicative competences and skills at different levels of language
structure. Typical language development progresses gradually from speech perception
to learning to associate objects and situations in the world with their linguistic labels,
and further on to understanding and producing sentences of increasing complexity,
and, ultimately, longer pieces of discourse and interaction mediated by language(Karmiloff, Karmiloff-Smith 2001).
Despite the observed variation in individual rates of development (Bretherton etal. 1983; Rescorla 1984; Huttenlocher et al. 1991), most children achieve the same257

milestones (e.g., first words, first two-word combinations) roughly around the sameage. In some cases, however, developmental disorders disrupt the process of typicaldevelopment by selectively affecting both the process of language learning and its
outcomes. Among developmental deficits which affect language, the most prevalent
one is Language Impairment (also labelled Developmental Language Disorder).
Its prevalence is estimated at 6–7% (Boyle et al. 1996; Tomblin et al. 1997), but
prevalence may vary depending on cut-off thresholds and instruments/criteria usedin the screening or diagnosis. Language Impairment (LI) adversely affects the child’s
ability to acquire language leading to poor outcomes in receptive and/or expressive
language skills. Affected children are likely to have language problems enduring into
middle childhood and beyond, with a significant impact on everyday social interactions
or educational progress (Bishop et al. 2017). While early delay in language may betransient, around half of the children with language delay may experience persistentproblems with language later on (Bishop, Edmundson 1987; Rescorla, Schwartz
1990; Rescorla et al. 1993; Thal, Bates 1988). Autism spectrum disorder (ASD) is apervasive neuro-developmental condition characterized by a constellation of earlyappearing social communication deficits and repetitive sensory-motor behaviours.
Like LI, the prevalence of autism may vary depending on the availability of screening
tools, referral practice and cut-off points. Current prevalence estimates for the USA are
1 in every 54 children (Maenner et al. 2016), while for the UK the prevalence estimate
is 1%. (Baron-Cohen et al. 2009). ASD is associated with a strong genetic component
as well as other causes (Lord et al. 2018). The range of structural language skills on
the autism spectrum is highly varied, whereby some affected children hardly produce
any speech (minimally verbal), while others may have adequate structural language
competence (highly-verbal) (Tager-Flusberg 2006). For this reason, according to theprevalent current view reflected in DSM-5 (American Psychiatric Association 2013),
the presence of language impairment is seen as a co-morbid condition, rather than the
primary impairment in autism. Still, even highly verbal individuals with autism haveproblems with discourse comprehension and figurative language processing, often
described as impairment in pragmatic language (Tager-Flusberg 2006; Vulchanova
et al. 2015; Chahboun et al. 2016; Vulchanova et al. 2019). Both LI and ASD impact
adversely on oral language outcomes in affected children. To the extent that oral
language is the primary mode of language acquisition and use, these two populations
will be of main interest for the current review.
In the first stages of language acquisition, very young infants are busy processing
the sounds of language. Research provides evidence that this process starts already inthe pre-natal stage while the foetus is in the womb, and already in the last trimester ofpregnancy, the hearing system is sufficiently well developed to appreciate a variety
of sounds, including language. More importantly, already at this stage, the foetus candiscriminate between different types of sounds, and can isolate language as a special
type, where sequences of sounds potentially have a special value (Mehler et al. 1988).
Needless to say, during the pre-natal stage, the quality of sound is very different fromsound that travels through air: the yet unborn baby is surrounded by liquid (i.e. theamniotic fluid) and sound is quite muffled. Research, however, documents that newly
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born infants are sensitive to voice quality and can distinguish between the mother’svoice and other female voices. They also show a specific preference for the mother’svoice as heard in the womb over the mother’s voice heard after birth, as well as astrong preference for the mother’s voice over other female voices. Importantly, young
infants prefer their own mother‘s voice provided the mother speaks with a normal
intonation (Mehler et al. 1978). There is a natural explanation for this phenomenon,
which is the result of rich exposure to language produced by the mother both prior
to birth and after birth. As a matter of fact, language experience through exposure
to language is by far the most important among environmental factors in language
development (Gathercole, Hoff 2007). Also, the preference for the mother’s voice
is explained through its high bonding value in the first months and years after birth.

1.2. Speech perception in infancy
During early speech perception, while distinguishing between different languages
and especially their intonational properties, infants gradually develop a preference
for their native language, and by the time they are 9 months old, sensitivity to otherlanguages and their sound systems declines dramatically. This very early sensitivity
window to speech closes before the first year of life, and the loss of sensitivity to
the sound systems of other languages provides some explanation to the anecdotally
attested difficulty in acquiring the pronunciation of foreign languages later in life.
Interestingly enough, infants raised bilingually seem to retain sensitivity to more than
one language beyond this time window, as documented in experimental studies on
Spanish/Catalan and English/French (Sebastian Galles et al. 2012; Weikum et al.
2007). This is one of many advantages that have been found for early bilinguals.
It has been shown that infant phonetic discrimination is initially language
universal, however, a decline in this ability is observed between the 6th and the 12thmonth after birth. It has been argued that this decline in early sensitivity to universal
phonological properties of language is associated, and correlates, with nativelanguage phonetic learning (Kuhl, Conboy, Padden et al., 2005). In a seminal study,
Kuhl and colleagues (2005) followed longitudinally a cohort of infants from the timethey were 7-month-old to 30 months of age. In that study native language phonetic
discrimination was a reliable predictor of later language skills in participating infants.
Thus, better native-language discrimination at 7 months predicted accelerated later
language abilities, whereas better nonnative-language discrimination at 7 months
predicted reduced later language abilities when tested at 30 months.
The study by Kuhl et al. (2005) highlights the role of early speech perception
as a predictor of later acquired language competences and skills. Thus, even thoughduring early speech perception, the infant is primarily occupied with processing
the sounds of language, without necessarily processing for meaning, early speech
perception plays an important role for the rest of language acquisition – it provides
a stepping stone for identifying potential words in the speech stream, later to learn
them as the labels of objects and situations the infants are surrounded by in theirambient environment. Being able to segment the speech stream into smaller units
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(e.g., possible words) is an important achievement which can be compared to learninga foreign language – originally it all merges into a never ending and unsegmentable
blur of sounds to the inexperienced ear. Infants gradually learn to break this codeand start identifying frequently and stably occurring sequences, which actuallycorrespond to words in the native language (Jusczyk 1997). There are many cuesthat infants can rely on in this process. Across languages, stress is an important clue
where a word ends and where a new one starts, thus helping in establishing wordboundaries. Some languages rely on tones, which distinguish between words, where
the same sequence of sounds produced with two different tones may mean two very
different things. This distinction can be found even in less exotic languages, such as
Norwegian (Nilsen 2000).
Other cues for word learning may lie in the so-called phonotactic rules of thelanguage. For each language there are namely legal and illegal combinations of sounds.
For instance, in Spanish the combination of „s“ and „p“ is illegal at the beginningof words. Thus, you need to add „e“ before them to make the word pronounceable
in Spanish (Spain – Espagna). Phonotactics is encoded in the orthography of thelanguage at hand and thus plays an important role in the acquisition of literacy. In
recent research we document that bilingual exposure to orthotactically dissimilar
languages may provide an advantage in the process of acquiring literacy skills(Borragan et al. 2020). We tested two groups of bilingual children, Spanish/Catalan(two languages which are orthotactically similar) and Spanish-Basque (orthotacticallydifferent), and compared the bilingual groups to monolingual children. The SpanishCatalan bilingual children performed similarly to the monolingual controls and weremuch better on recognition of words that followed the orthotactic rules of their native
languages (i.e., legal words), while the Spanish-Basque bilingual children showed
equal performance in learning illegal and legal patterns. These findings suggestthat bilinguals with dissimilar languages are more flexible in also considering new
and potentially possible orthotactic patterns. This pattern of performance in the
Spanish-Basque bilinguals is reminiscent of the attested sensitivity to universal
phonological properties in the first months after birth (Kuhl et al. 2005) and suggeststhat the window of learning phonotactic/orthotactic rules is still open in that groupof bilingual children. Furthermore, we demonstrate that word learning is not affectedby bilingualism as such, but rather depends on the bilinguals‘ specific linguistic
experience at this age.
While speech perception helps in word learning, early speech production is quite
different in nature. Here, the infant needs to train its vocal apparatus in order tomaster and perfect producing the specific sound sequences of their native language.
The individual sounds of each language require a lot of effort to produce by featuring
subtle variations in the quality of the sound and place of articulation. Thus „p“ and „b“
are distinguished solely on the basis of „voiced“ quality. Giving motor instructions
to your lips and tongue is quite a feat, and infants start practicing already in thesecond half of their first year of life by engaging in the activity typically referred to as
babbling. Here they produce combinations of vowels and consonants (baba, dada),
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and often more complex sequences often resembling existing words in the language.
Parents would sometimes proudly take this as word production, however, it is the firststeps at mastering speech production.

1.3. Words, words, words
Early word learning is a very intriguing process. It requires a lot of previously
acquired skills, such as identifying the sound pattern that corresponds to a specificword, and as such, largely depends on early speech perception. A second important
step is the ability to identify what aspect of the world this sequence of sounds possibly
describes. Is it an object (a dog/cat/cup), a situation (running/eating), a property (nice/red/stupid), or some relation between objects (the spoon is IN the cup)? The infinite
possibilities in how words map onto objects and events out in the world has become
known as the „Gavagai“ problem and can be traced back to a philosophical mental
experiment first described by Quine (Quine 1960).
There are many cues that infants can follow in the process of word learning. One
important cue is the ability to follow the caregiver’s attention, a phenomenon known
as joint attention. This ability may be impaired in children with autism, and is often
assumed as one of the causes of the delay in their language development. The ability
to form categories (e.g., perceiving similarity between objects of the same type) is
another crucial competence. Furthermore, research suggests that often categorization
and word learning go hand in hand and assist each other, and children have been shown
to more readily form categories in the presence of language labels (e.g., in experimentswith invented words (i.e. pseudo-words) vs. pro-forms, e.g. „Show me the blick“ vs.
„Show me this one“). Thus, it is impossible to state whether categorization leads wordlearning or whether word knowledge is a necessary prerequisite for early categorization.
Interesting evidence comes from work conducted by Linda Smith and her colleagues,
where studies have shown the importance of object shape in the process of wordlearning (Yee et al. 2012). Interestingly, changes in the visual recognition of objects
precede the observed shape bias in noun learning. From that work, it becomes clearthat shape supersedes colour, texture and other object properties in the process of wordlearning. In addition, this work shows that the visual affordances of objects, and object
shape, in particular, provide a cognitive backdrop for the acquisition of language labels.
Studies addressing early word learning document that elaborate processes are
already in place. Infants and toddlers respond to sound similarity between words
suggesting a growing vocabulary, and later on become sensitive also to semantic
similarities between the meanings of words (Mani, Plunkett 2010).We have evidence
that the infant „mental“ lexicon (i.e, all the words that the infant can recognize andproduce) gradually grows in size and density, with an increasing number of newconnections between newly learned words and already existing word knowledge(Mani et al. 2012). A recent theory suggests that children actually learn the words
they want to learn (Mani, Ackerman 2018), and this might explain, in part, thedocumented differences in vocabulary knowledge between boys and girls.
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1.4. Language structure
While words are important in order for the child to be able to name objects,
acquiring the hidden rules of grammar of the native language is what ultimately leads
to understanding complex utterances, in both oral communication and when reading
texts. Grammar competence lies at the heart of later academic skills, which require
access to content in written form (e.g., in textbooks or on-line learning materials). As
such, it is also a major predictor of how well children will understand texts at school,
and will communicate their thoughts both orally and in a written form. Grammar
competence in the native language has also been shown to determine comprehension
in a second language, e.g. a language the child learns later at school. In a study of alarge sample of 10-year old Norwegian children we documented reliable correlations
between phonological memory and working memory and overall language skills inboth Norwegian (first language) and English (an early second language) (Vulchanova
et al. 2014). More importantly, English sentence comprehension in our participants
was predicted directly by their first language (Norwegian) grammar/syntax
competence as measured on a comprehensive language test battery. At the early stagesof language acquisition, vocabulary and grammar appear to be inseparable, and earlyword knowledge has been found to both correlate with, and predict, later grammar
skills around the second year of life (Bates, Goodman 1997). Later, after the firstschool years, word knowledge, grammar and discourse skills emerge as independent
components of the language faculty, and can be identified as separate dimensions(LARC 2015). This simply means that they can be studied in the child independently,
and are less interrelated in middle childhood and adolescence.

1.5. Pragmatic language development
Pragmatic language is a cover term applying to language competences
and skills which operate at a level beyond syntax. These are typically related to
discourse comprehension, the ability to understand language in context, but also
the interpretation of non-literal figurative language, such as jokes, irony, indirect
requests, idioms, metaphors. The reason why these skills emerge later is not only
because they are scaffolded by earlier skills, such as adequate vocabulary knowledge
and advanced syntax competence. In addition, their emergence is associated withthe acquisition of foundational literacy and, through literacy, with richer exposure to
written language, and, thus, exposure to more and more varied registers of the native
language (Levorato et al. 2004; Cain et al. 2008; Vulchanova et al. 2015).
Figurative language displays exponential non-linear development between
the pre-school years and middle childhood. Research in idiom comprehension andprocessing in children (Benneli et al. 2006, Levorato, Cacciari 2002), has further
suggested that the ability to work with figurative language (including idioms)
correlates with age and years of schooling and is linked to other linguistic abilities,
such as meta-linguistic awareness, and the ability to infer from context (Bernicot etal. 2007).
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In a study designed to test for the first time idiomatic knowledge in younger
children (6–7 years), and older children (9–10 years) with Bulgarian as a first
language (L1), as compared to adults, we show that, while idiom comprehension
is scarce among the younger group, children aged 9–10 display advanced linguistic
skills and are capable of providing elaborate definitions and synonyms for the target
items (Vulchanova et al. 2011). Our study also shows that children only resort toliteral interpretations in the cases when they do not know the idiom, and that some of
their „incorrect“ responses reflect an embodied perspective on language (Simmons
et al. 2003). Our results indicate that different types of idiomatic expressions present
different types of challenges for the learner and are acquired differently. For instance,
idioms like „Да се измокря до кости“ (get soaking wet (lit. „get wet to the bones“),„Да си спася кожата“ (save one’s skin) and „Хлопа му дъската“ (have a screw
loose) were familiar also to the younger participants, and received close to ceilingperformance in the older children. Such idioms are biologically motivated in thatthey build on analogies involving parts of the body, and, as such lexicalize andencode the basis of human experience. There is strong evidence that many of them
are shared across cultures, and we find almost word-by-word equivalents across the
Indo-European languages, but also Finnish (cf. Penttilä et al. 1998). Biologicallymotivated idioms belong to the category of early acquired non-literal expressions andtheir acquisition plateaus around 11–12 years. In contrast, culturally-based idioms„Гладна мечка хоро не играе“ (hungry bellies have no ears (lit. „a hungry bear
would not dance“); „Свалям картите на масата“ (lay/put your cards on the table)
which reflect cultural and often idiosyncratic aspects of the language, are acquired
gradually and along the life-span. One cultural idiom, „Работи, без да подвие
крак“ (’work without rest’ („work without twisting/bending a leg“) was particularly
challenging for the child participants. We hypothesize that this is the case because
the expression is based on an obsolete (idiosyncratic) lexicalization pattern. From thepoint of view of the modern language, the verb подвие (‘twist/bend’) is odd in thecontext of the direct object крак (‘leg’). The expression, as a whole, refers to a sitting
posture where your legs are placed under your body and are bent. However, it isarchaic and not transparent to the modern speaker. Furthermore, it is highly likely thatobsolete expressions of this type are less frequent in the input children are currently
exposed to, thus reducing opportunities for becoming familiar with the expression.

1.6. Gesture and language
Gesture and speech form a unitary communication system whereby they areclosely aligned both semantically and temporally (McNeill 1992; Cooperrider,
Goldin-Meadow 2017). Gesture comprehension, and specifically, gesture production,
are inherently linked to emerging communicative skills in the child, and are earlyprecursors of later language skills (Butterworth 2003; Iverson, Goldin-Meadow2005). The distinctive use of hand for communicative purposes signals infants’socio-cognitive development (Tomasello et al. 2007) and their readiness for spoken
language acquisition (for a meta-analysis see Colonnesi et al. 2010). As a matter of263

fact, the cognitive underpinnings of pointing are at the very heart of communication
development and make apparent the link between gestures, cognition and language(Kita 2003). Among early gestures, pointing (deictic) gestures have been shown to
be closely linked to later language development. In contrast to other deictic gestures(i.e. showing and giving), pointing allows for reference-making without necessarily
establishing contact with the referent. Pointing production thus implies the acquisitionof the cognitive skills necessary to go beyond pure object manipulation and engage
in symbolic reference from a distance. Pointing is also the only gesture type thathas been shown to reliably predict language in both typically developing children(TD) and children with autism (Özçalışkan et al. 2016; Ramos-Cabo et al. 2019 fora review).
Research in developmental deficits documents that gesture is often impairedin children with autism and Developmental Language Disorder (DLD) (BaronCohen 1989; Goodhart, Baron-Cohen 1993; Camaioni et al. 2003). In a recent study
we document that deictic gestures are not only quantitatively affected, but also
qualitatively impaired in children with an autism diagnosis in comparison to typicallydeveloping children and children at high risk for autism (Ramos-Cabo et al. 2021).
Thus, gesture production can be used as an early marker of atypical communicative
function.

2. Factors in language development
2.1. Biological and cognitive factors
There are broadly two types of factors that impact on the process of acquiring
the native language: biological and environmental. Among the biological factors,
we can mention brain maturation, which determines brain plasticity. This is also
known as the sensitive period for language acquisition, a favourable window in thelife of the child, during which language can be acquired optimally. Even though
it is uncertain whether this period has a clear terminus, i.e. a point beyond which
language acquisition cannot be successful and cannot reach ultimate attainment oflanguage competence, there is evidence that the ability to acquire language declines
with age. A recent large-scale study of both native speakers and second language
learners of English in the USA has established that indeed the language learning
ability declines in late adolescence (Hartshorne et al. 2018). This decline can be partly
explained in terms of the gradual loss of brain plasticity, meaning that, as adults, weare less open to learning new skills. Other accounts would rather focus on the adultcognitive status, which differs from that of children, and the fact that children havefewer, and possibly, less sophisticated, cognitive resources available to them. As aresult, they can learn language better than adults, an account come to be known as
Elissa Newport’s less-is-more hypothesis (https://www.psychologicalscience.org/
publications/observer/25at25/elissa-l-newport.html).
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Other biological factors that might play a role in language development are
gender differences (also observed in brain maturation).
Among cognitive factors, phonological memory and working memory determine
how well the child can store and manipulate sounds and sound segments, a coremechanism which underlies language learning. Often, this ability can be impaired indevelopmental deficits (e.g., developmental language deficit/language impairment,
reading impairment), which, in turn, affects the course and trajectory of learning.

2.2. Environmental factors
By far the most important environmental factor in language development is
the language ecology of the child, the language it is exposed to. This is language
the child hears from caregivers (parents, grand-parents), teachers in pre-school, andpeers (children of the same age as the child). This exposure makes it possible for thechild to benefit from the variation of the language used, whether in terms of dialects,
idiolects or generational differences in language use. It is exactly rich variation in thelanguage input that ultimately leads to successful generalization across contexts andacquisition of the main aspects of language: from sound, to word to grammar, andthe rules that underlie their use. In addition, social factors, such as early child-adultinteraction, parental education and involvement with the child have been shown toplay an important role.
Bilingualism provides important evidence of the role of exposure to language
input. In an increasingly global world children are raised in bilingual, and often,
multilingual environments. Children who are exposed to two or more languages fromearly on (around birth and during the first years of life) are thus likely to acquire
both languages without effort and develop balanced competences in both languages(Werker, Byers-Heinlein 2008; Klein et al. 2014). However, the extent to whichbilingual individuals attain competence in the languages they are exposed to depends
on the complex interplay of multiple factors, including age of exposure to the languagein question (the biological constraints on language acquisition), quantity and qualityof input (language environment), and language activity and use (e.g., how often andfor what purposes the language is used) (Genesee, Nicoladis 2007; Grosjean 2001).
Importantly, the biological and environmental factors in language development
work in synergy, and successful language acquisition is brought about through the
dynamic interaction between nature and nurture. This means that genes do not operate
in a deterministic way, and that learning itself impacts on brain development in thecourse of this interaction.
At present, a new important factor is already affecting human culture, behaviour
and cognition, and is changing our children’s lives and childhood dramatically. New
technologies create environments that could alter how we process information, thedegree to which we take risks, how we socialize and empathize with others and even,
how we view our own identity. Parents experience that toddlers can handle digital tools
with a level of sophistication that they can only envy. We are immersed in a ‘digital
ecology’ increasingly populated by devices that are both tools at our disposal and265interactive agents with a degree of autonomy. While software development in both theentertainment and learning domain is advancing at a fast and unprecedented rate, andschools are spontaneously adopting digital solutions for the acquisition of academic
skills, such as literacy, at present, there is no adequate research base documenting theeffects of digital tools on language or other learning outcomes in young children. Neither
are current software solutions based on developmental, educational or psycholinguistic
principles. Thus, we are facing the consequences of what educational and cognition
researchers have called „a vast unplanned experiment“ (Hirsh-Pasek et al. 2015). An
open question is to what extent the increasingly digital environments will equip young
children with an adequate type of input concerning language acquisition, and whether
this exposure will have positive or negative consequences (e.g., in comparison tointeraction with human caregivers) (Vulchanova et al. 2017).
It has been maintained that the nature of the language to be acquired does not playa decisive role in the process of language acquisition and its successful outcome. Thus,
whether the child is exposed to a richly inflected language (such as e.g., Finnish) or alanguage with poor morphology (e.g., English), is generally not expected to play a rolein success in acquisition and whether the child achieves ultimate attainment or not.
Interestingly, however, research has documented that, despite being more challenging,richly inflected languages may trigger more efficient (and faster) acquisition ofgrammatical categories. A study comparing 1001 English-speaking children and 386
Italian-speaking children between age 1;6 and 2;6 demonstrates large cross-linguistic
differences in the amount of morphology that has been acquired in children matched forvocabulary size, as well as small, but intriguing differences in the shape of the growth
curve for grammatical function words (Caselli et al. 1999). These results indicate thatchildren acquiring a morphologically complex language (e.g., Italian) possess moreadvanced grammar competence in comparison to children of the same age exposed to amorphologically impoverished language, like English. This appears to be a consequenceof the richer cues that Italian provides for the learner and can be explained in termsof the Competition Model (Bates, McWhinney 1982), whereby cue availability andreliability play a role in determining the order of acquisition of grammatical structures.
Such cues may, in turn, recruit and more strongly activate the use of Statistical Learning,a powerful experience-dependent mechanism heavily implicated in the process oflanguage acquisition (Saffran et al. 1996; Saffran 2003). Interestingly, there is emerging
evidence that some languages may prove more challenging for the language learner.
A recent conceptual review suggests that, unlike closely related languages, such ase.g., Norwegian, Danish has an unusually reduced phonetic structure, which seemingly
delays Danish-learning children in several aspects of their language acquisition (Trecca
et al. (in press)a; Trecca et al. (in press)b).

2.3. Other factors
Parents often wonder whether instruction plays a role in native language
development. Based on the evidence we have from research, and numerous
observations, it can be safely stated that infants and young children do not respond266

to correction or instruction on part of the parents. Thus, oral language development
depends on the subtle weighting of, and synergy between, the biological andenvironmental factors, but not on explicit instruction. Importantly, however, theacquisition of literacy in the native language requires a certain deal of instruction,
especially in the first years of school. Instruction or modelling behavior can also beseen as beneficial in the provision of intervention for children with developmental
deficits. Often during intervention, the speech and language therapist provides an
explicit model, which the child can follow, e.g., asking specific types of questions orcomparing words and their meaning or model sentences in order to practice different
types of constructions (a practice often called reinforcement).
Another factor, which often comes to mind in the context of language
development, is motivation. Given rich exposure to language in the environment andsufficient interaction with both parents and peers, it can be imagined that motivation
has no role. Some researchers have emphasized the social and communicative value of
language as encouraging a type of inherent motivation to learn language. Indeed, forthe developing child, becoming aware of the power of language in both establishingand maintaining social bonds, is an important incentive to learn to use that code. In
addition, new research suggests that there might be an inherent reward in learning
language. A word learning study by Antoni Rodriguez-Fornells and his colleagues(Ripolles et al. 2014) provides evidence that successful word acquisition activates
brain areas supporting reward mechanisms in the brain. This comes to suggest that
there may be an even deeper inherent drive to acquire language, also seen from an
evolutionary perspective.

3. Language development in developmental deficits
Children with developmental deficits often experience problems with language.
In children with language impairment (also currently known as Developmental
Language Disorder) biological factors conspire to compromise the very process oflanguage development, ultimately leading to impaired outcomes. It has thus beensuggested that inadequate language skills are the consequence of (impaired) language
learning (Bishop 2013). Such children will experience problems in producing speech
and word learning, but most commonly the problems are present in core aspectsof grammar, such as word inflections and sentence structure. Whereas the mostpronounced problems in children on the autism spectrum are in social communicationand interactions, as well as the presence of repetitive behaviours and lack of flexibility,
most children with an autism diagnosis will also experience problems with aspects oflanguage. While for children on the low end of the spectrum, the language problems
may be pervasive, for children on the high end (often called high-functioning or
highly-verbal), structural aspects of language will be largely intact. However, evenfor those children, subtle problems remain, such as e.g, in the understanding of nonliteral language found in idioms, metaphors, jokes, irony and humour (Vulchanova
et al., 2015; Chahboun et al., 2016; Vulchanova et al, 2019). Whether these problems
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are related to the core deficit or to language competence is yet to be established, andthe source of these problems is still open to debate and future research. Children
with a reading problem will primarily have problems with the sound structure of thenative (or other languages) and its mapping to orthography (the written form of thelanguage). Some research provides evidence that there may be additional factors,
such as, morphological skills, which impact on (impaired) reading, and this mightalso depend on the word structure of the language in question and how it is encoded
in its orthography.
Children with language-related disorders often present with word learning
problems (see Vulchanova et al. 2020 for a review). Such problems may affect either
the acquisition of phonological aspects of the word (word form) or aspects of word
meaning, depending on the type of deficit. Thus, children with DLD struggle withproblems related to word form/morphology (Nation 2014), whereas the acquisitionof word semantics is more challenging for children with autism (Norbury et al.
2010). Such dissociations in word learning, which lead to poor outcomes in word
knowledge, provide corroboratory evidence of theoretical and psycholinguistic
models of word knowledge (Levelt 1989) and representation (e.g., Perfetti’s Lexical
Quality Hypothesis – Perfetti, Hart 2002; Perfetti 2007).
In most cases of language-related developmental deficits, affected children will
display a marked delay in the development of specific aspects of language compared tosimilarly aged children. Thus, an important task for parents is to closely observe how
the child is acquiring the native language and seek advice or screening for language,
if there is concern that the child is not developing on track. Also, sudden changes
in the language trajectory (e.g., a „mute/silent“ period or regression in previously
attained language skills) should be cause for concern.

4. Concluding remarks and aspects worthy of notice
An important feature of typical language development is the well attested big
individual variation in language skills in the course of development. This variationis the product of the biological and environmental forces that impact on language
development and is quite natural. In a similar way, the child’s receptive skills vastly
outstrip her/his expressive skills, a phenomenon clearly observed in the early years.
Thus, it takes almost a year before the infant starts producing language (mainly
words), even though they are perfectly capable of understanding simple messages andinstructions long before that. The asymmetry between comprehension and production
is a well-established fact, and should not cause any concern, if observed. It deserves
notice that in a global world, many children will be raised bilingually. Their language
skills in both languages will largely depend on their language ecology (e.g., howoften and for how long they are exposed to the languages they are acquiring; whether
one of the languages is dominant or not; the family language practices). A crucial
factor in bilingual language outcomes is the age of onset, meaning when the childstarts learning the language. In the past there have been concerns among educators
268

and parents that acquiring two languages simultaneously may cause a delay, evenconfusion in the child. However, research over the past 40 years provides ample
evidence that bilingual children can succeed in acquiring both languages given
optimal conditions: rich and varied exposure and early onset (Werker, Byers-Heinlein2008). How well adults learn new languages will depend again on their learning
environment, e.g., whether in a classroom or through immersion in the culture andthe language. Yet, given that there is a sensitive period for language, we might expectthat their language skills in that second language will not be optimal.

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Useful links to on-line material:
The child’s mind: https://www.ted.com/talks/patricia_kuhl_the_linguistic_genius_of_babies
Early word production: https://www.ted.com/talks/deb_roy_the_birth_of_a_word
Word learning: https://bold.expert/why-do-children-learn-the-words-they-do/Child-Directed Speech: https://www.sciencealert.com/amotheresea-helps-kids-speak
Language
Impairment:
http://deevybee.blogspot.com/2013/09/raising-awareness-oflanguage-learning.html
Early Language Development in the Digital Age (large-scale Horizon2020 project): https://www.ntnu.edu/e-ladda/
Mila Vulchanova, Valentin Vulchanov
Language Acquisition and Language Processing Lab
Norwegian University of Science & Technology – Norway
Valentin Vulchanov
Acknowledgements
Language
Acquisition
and Union’s
Language
Processing
Work on this project has received fundingfrom
the European
Horizon2020 Lab
research
and innovation programme under theMarie Sklodowska-Curie
Actionsagreement
No 857897
Norwegian
University of Science& grant
Technology– Norway273