Human bonding
The term human bond -- or, more generally, human bonding -- refers to the process or formation of a close personal relationship, as between a parent and child, especially through frequent or constant association.  When pairs have favorable bonds, the nature of this bonding is usually attributed to "good" interpersonal chemistry.  The word bond derives from the 12th century Middle English word band, meaning something that binds, ties, or restrains.  Its application to interpersonal human relationships has been used intermittently ever since.
The term social network or "interconnected group of people", which may include up to 150 people (Dunbar's number), is from 1947.  The concept of nuclear family or bonded unit of two parents plus one or more children was coined by American anthropologist George Murdock in his 1949 work Social Structure.  According to Merriam-Webster, the application of the term bonding to interpersonal relationships came of use in 1976.  With the recent popularity of the Internet, sites such as MySpace encourage people to increase the size of their friendship networks.

# Early views
In the 4th century BC, the Greek philosopher Plato argues that love, in a way, directs the bonds of human society.  In his Symposium, Eryximachus, one of the narrators in the dialog, states that love goes far beyond simple attraction to human beauty: It occurs all throughout the animal and plant kingdoms, as well as all throughout the universe.  Love directs everything that occurs, in the realm of the gods as well as that of humans (186a-b).
Eyrximachus reasons that when various opposing elements such as wet and dry are "animated by the proper species of Love, they are in harmony with one another . . . But when the sort of Love that is crude and impulsive controls the seasons, he brings death and destruction" (188a).  As it is love that guides the relations between these sets of opposites throughout existence, in every case it is the higher form of love that brings harmony and cleaves toward the good, while the impulsive vulgar love creates disharmony.
He concludes that the highest form of love is the greatest; when love "is directed, in temperance and justice, towards the good, whether in heaven or on earth: happiness and good fortune, the bonds of human society, concord with the gods above- all these are among his gifts" (188d).
In the 1660s, the Dutch philosopher Spinoza writes, in his Ethics of Human Bondage or the Strength of the Emotions, that the term bondage relates to the human infirmity in moderating and checking the emotions.  That is, according to Spinoza when a man is prey to his emotions, he is not his own master, but lies at the mercy of fortune.
In 1809 Johann Wolfgang von Goethe, in his classic novella Elective Affinities, speaks of the marriage tie and by analogy shows how strong marriage unions are similar in character to that by which the particles of quicksilver find a unity together though the process of chemical affinity.  Goethes novella, in its time, was regarded as treatise on chemical origins of love.  Humans in passionate relationships, according to Goethe, are analogous to reactive substances in a chemical equation.

# Bond varieties
The term bonding applies aptly to all variations of connections within interpersonal relationships, social networks, economic nexuses, political ties, etc.  The term male bonding refers to bonding between males through shared activities excluding females or the formation of a close personal relationship between men; for example: "the rituals known as male bonding do not necessarily involve drinking beer together".  The analog concept female bonding, although less frequently used, refers to the formation of a close personal relationship between women.
The familial bond defines as a uniting force, tie, or link between related family members.  A related concept is bondage, being the tenure of service of a villager, serf, or slave and generally refers to a state of being bound by compulsion as via law or mastery;  a bondmaid is a woman servant, a bondman is a male servant, and a bondsman is a person who provides bonds or surety for another.  In the 14th century, a bondwoman was considered a female slave. The distinction is that "bonding" almost always implies a voluntary act, of entering in or remaining in relationship from a wish to do so.
A comparable analog is labor union, originating in 1866, being an organization of united workers formed for the purpose of advancing its members interests in respect to wages, benefits, and working conditions.  The cohesion of the group is facilitated by the exchange of union dues for benefits.  By uniting, the bonded group has more leverage than as compared to a collection of separate individuals.
Similar to the marriage bond, is concept of civil union.  A civil union is one of several terms for a civil status similar to marriage, typically created for the purposes of allowing same-sex couples access to the benefits enjoyed by married opposite-sex peoples (see also same-sex marriage);  it can also be used by opposite-sex couples who do not prefer to enter into the legal institution of marriage but who would rather be in a union more similar to a common-law marriage.  With the popular success of the hit television show Queer Eye For The Straight Guy and others such as The Ellen DeGeneres Show, the term gay-straight bonding as well as gay bonding have come into vogue.

## Other
- Connector - people in a community who know large numbers of people and who are in the habit of making introductions.
- Homophily, i.e., love of the same, is the tendency of individuals to associate and "bond" with similar others.
- Gemeinschaft - a spontaneous organic social relationship characterized by strong reciprocal "bonds" of sentiment and kinship with in a common tradition.
- Clique - an informal and restricted social group formed by people who share common interests, which are often associated with teenagers.
- Mother-bonded - a term for a man who is excessively attached to his mother at an age when men are expected to be independent, e.g. living on their own, being economically independent, etc.

# Interpersonal chemistry
Metaphorically, a chemical reaction between two people involves either the formation of a bond or dissolution of a bond, or some combination thereof, and the psychodynamics associated with this process.  In this direction, in the fields of sociology, behavioral psychology, and evolutionary psychology, with specific reference to intimate relationships or romantic relationships, interpersonal chemistry is a reaction between two people or the spontaneous reaction of two people to each other, especially a mutual sense of attraction or understanding.  In a colloquial sense, it is often intuited that people can have either good chemistry or bad chemistry together.   Other related terms are team chemistry, a phrase often used in sports, and business chemistry, as between two companies.  Recent developments in neurochemistry have begun to shed light on the nature of the "chemistry of love", in terms of measurable changes in neurotransmitters such as oxytocin, serotonin, and dopamine.

# Bond distinctions
A common division when referring to the structural integrity of relationships or unions is to divide such bonds via a physical and a neurological component, which may or may not co-occur, i.e. into:
- Physical bond  two people bonded owing to physical adhesion.
- Neurological bond  two people bonded owing to neurological adhesion.
The physical bond is typically sexual in nature, i.e. a sexual bond, although it may refer to individuals bonded by proximity as neighbors or by blood as siblings.  People bonded physically typically have a visceral connection, either via pheromone exchange, visual attraction, hormonal adhesion, etc.  The neurological bond covers all varieties of mental attachment, as psychological bonds, intellectual bonds, emotional bonds, financial bonds, synergistic bonds, altruistic bonds, etc.
In 1939 psychologist Godfrey Thomson, in his Factorial Analysis of Human Ability, for example, posited theoretical bonds of intelligence which function in loving relationships.  In Sternbergs 1986 Triangular Theory of Love, he defined Thomsons theory as a structural model of love where we might conceptualize love in terms of feelings that, when sampled together, yield the composite experience that we label love.  Here, the composite is not an undifferentiated unity; rather, it can be decomposed into a large number of underlying bonds that tend to co-occur in certain close relationships.  With reference to the triangle theory, Sternberg relates the passion component of his triangle to the physical bond and the intimacy and decision/commitment components of the triangle to the neurological bond, both of which vary in strength and intensity throughout each stage of the relationship, i.e. dating, transition, marriage, etc.
Similarly, in recent the 2006 National Geographic article Love the Chemical Reaction photo journalist Lauren Slater asks: Does passion necessarily diminish over time?  Can a marriage be good when Eros is replaced with friendship, or even economic partnership, two people bound by bank accounts?  Referring to her eight-year marriage, she states: The ties that bind have been frayed by money and mortgages and children, those little imps who somehow manage to tighten the knot while weakening its actual fibers.

# Neurochemistry
Main bonding chemicals
- Oxytocin   bonding molecule (hormone): high levels correlate with strong pair-bonding.
- Vasopressin  monogamy molecule (hormone)
- Endorphin - calming natural pain killer
Related bonding chemicals
- PEA   amphetamine molecule (neurotransmitter)
- Dopamine   desire molecule (neurotransmitter): levels increase as passion levels increase.
- Serotonin   stability molecule (neurotransmitter)
- DHEA   most abundant hormone
- Prolactin  motherly hormone (stops female and male sex-drive)
- Testosterone   masculinization hormone (high testosterone-laden males tend to bond with high estrogen-laden females)
- Cortisol - the primary hormone product of the adrenal glands; helps restore homeostasis after a state of stress.
- Estrogen  feminization hormone (high estrogen-laden females tend to bond with high testosterone-laden males)
- Androsterone   a pheromone attractor
- Squalene   a pheromone repellant (stops male courtship behavior in snakes)
- Progesterone   reverse sex-drive hormone
- Norepinephrine  - elevated levels are associated with romantic love.
- Nerve growth factor - neuro-protein that stimulates cell growth; higher levels are found with those newly in love as compared to those single or in long-term relationships.
Related facts
- The ventral tegmental area and the caudate nucleus become more active when madly in love.
- When looking at a lovers photo the anterior cingulated cortex and the basal ganglia become more active.
- When looking at a lovers photo the posterior cingulated gyrus and the right pre-frontal cortex become less active.
- During the first six months of love, serotonin levels drop to 40 percent below those in normal subjects.
- Women are vomeronasally-attracted to men with dissimilar major histocompatibility complexes.
- Males in love have decreased levels of follicle-stimulating hormone (FSH).  In men, FSH enhances the production of androgen-binding protein by the Sertoli cells of the testes and is critical for spermatogenesis.

# Types

## Pair bond
Pair-bond, originating in 1940 in reference to birds in mating, is a generic term signifying a monogamous relationship or a socially monogamous relationship of either the human or animal variety, commonly used in sociobiology and evolutionary psychology.  Pair-bonding, usually of a fairly short duration, occurs in a variety of primate species. Some scientists speculate that prolonged bonds developed in humans along with increased sharing of food. In recent years, some have begun to apply the term to human relationships arguing, for example, that a recent shift in technology, namely birth control and DNA testing, have created a shift in the male-female power balance thus resulting in the formation of dynamic pair-bond that do not exist in other species.

## Maternal bond
Of all human bonds, the mother-infant bond or maternal bond is the first to develop and considered to be one of the strongest.  The maternal bond begins to develop during pregnancy; following pregnancy, the production of oxytocin during lactation increases parasympathetic activity, thus reducing anxiety and theoretically fostering bonding.  It is generally understood that maternal oxytocin circulation can predispose some mammals to show caregiving behavior in response to young of their species.
Breastfeeding has been reported to foster the early post-partum maternal bond, via touch, response, and mutual gazing.. This effect is not universal, however, especially if problems with breastfeeding occur. It is difficult to determine the extent of causality due to a number of confounding variables, such as the varied reasons families choose different feeding methods. Many believe that early bonding ideally increases response and sensitivity to the child's needs, bolstering the quality of the mother-baby relationship  however, many exceptions can be found of highly successful mother-baby bonds, even though early breastfeeding did not occur, such as with premature infants who may lack the necessary sucking strength to successfully breastfeed.

## Paternal bond
In contrast to the maternal bond, in terms of variation in strength and stability, the father-infant bond or paternal bond tends to vary greatly over the lifespan of a childs development and growth and in many cases does not exist.  Many children, for example, in modern times, grow up in fatherless households.  In general, paternal bonding is more dominant later in a childs life after language develops.  Father-child bonds tend to develop with respect to topics and areas such as political views or money; whereas mother-child bonds tend to develop in relation to topics such as religious views or general outlooks on life.
In 2003, researcher from Northwestern University in Illinois found that progesterone, a hormone more usually associated with pregnancy and maternal bonding, may also control the way men react towards their children.  Specifically, they found that a lack of progesterone reduced aggressive behaviour in male mice and stimulated them to act in a fatherly way towards their offspring.

## Affectional bond
In 1958, British developmental psychologist John Bowlby published the ground-breaking paper "the Nature of the Child's Tie to his Mother", in which the precursory concepts of "attachment" were developed.  This later led to the development of the concept of the affectional bond, sometimes referred to as the emotional bond, which is based on the universal tendency for humans to attach, i.e. to seek closeness to another person and to feel secure when that person is present. Attachment theory has its origins in the observation of and experiments with animals. Much of the early research on attachment in humans was done by John Bowlby and his associates.  Bowlby proposed that babies have an inbuilt need from birth to make emotional attachments, i.e. bonds, because this increases the chances of survival by ensuring that they receive the care they need.

## Weak ties
In 1962, Mark Granovetter, a freshman history major at Harvard, became enamored with the concepts underlying the classic chemistry lecture in which "weak" hydrogen bonds hold huge water molecule together, which themselves are held together by "strong" covalent bonds.  This model was the stimulus behind his famous 1973 paper The Strength of the Weak Tie, which is now considered a classic paper in sociology.
Thus, weak social ties, or weak ties, it is argued, are responsible for the majority of the embeddedness and structure of social networks in society as well as the transmission of information through these networks.  Specifically, more novel information flows to individuals through weak than through strong ties. Because our close friends tend to move in the same circles that we do, the information they receive overlaps considerably with what we already know. Acquaintances, by contrast, know people that we do not, and thus receive more novel information.

## Limerent bond
According to limerence theory, positioned in 1979 by psychologist Dorothy Tennov, a certain percentage of couples may go through what is called a limerent reaction, in which one or both of the pair may experience a state of passion mixed with continuous intrusive thinking, fear of rejection, and hope.  Hence, with all human romantic relationships, one of three varieties of bonds may form, defined over a set duration of time, in relation to the experience or non-experience of limerence:
- Affectional bond: define relationships in which neither partner is limerent.
- Limerent-Nonlimerent bond: define relationships in which one partner is limerent.
- Limerent-Limerent bond: define relationships in which both partners are limerent.
The constitution of these bonds may vary over the course of the relationship, in ways that may either increase or decrease the intensity of the limerence.  The basis and interesting characteristic of this delineation made by Tennov, is that based on her research and interviews with over 500 people, all human bonded relationships can be divided into three varieties being defined by the amount of limerence or non-limerence each partner contributes to the relationship.

## Erotic bond
In the 1988 book Love Maps psychologist John Money postulated the existence of the erotic bond.  According to Money, each person is theorized to have a correlative love map based on his or her upbringing and experiences.  This concept is frequently referenced in interpersonal-relationship discussions.
A love map may make note of both positive and negative factors, things that attract or repel the person whose erotic tastes are being mapped. For reasons that are not always easy to understand, one person may be attracted to people of a particular gender, people with particular physical characteristics (such as hair color), people with particular personality traits (e.g., a sardonic sense of humor), and so forth. One may also find certain characteristics so threatening or objectionable (again, for reasons that may be difficult or impossible to ascertain) that it strongly mitigates against an erotic attraction being manifested.  Using this love map, a person unconsciously makes note of the personal and environmental factors that facilitate the formation of an erotic bond.

## Limbic bond
In 2000, psychologists Lewis, Amini, and Lannon published their famous A General Theory of Love in which they postulated the concept of the limbic bond, which defines a bodily connection that is limbic in nature. They also refer to this bond as a mammalian bond being that mammals in contrast to reptiles have a limbic system, which is why reptiles abandon their young after birth whereas mammals do not.
In the limbic bond, a mutually synchronizing sensory exchange as bodily warmth, olfactory cues, vocal exchange, visual interactions, etc., function to keep ties or organizing sensory channels between connected individuals.  These ties or bonds function to regulate those associated persons.  They define this design as an open-loop regulatory system; where, as they state, adults are social animals: they continue to require a source of stabilization outside themselves.  The open loop design means that in some important ways, people cannot be stable on their own; stability means finding people who regulate you well and staying near them.

## Societal bond
The societal bond refers to those cohesive elements and structural ties, as economic activity, unions, trade, sanctions, etc., which function to bind societies into collective units.  According to encyclopedia.com, marriage functions to cement the societal bond.  As they state, in many societies marriage links not just nuclear families but larger social formations as well.  Some endogamous societies are divided into exogamous groups, as clans or lineages.  Here, men form alliances through exchange of women, and the social organization regulates these alliances through marriage rules.

## Human-animal bond
The human-animal bond can be defined as a connection between people and animals, domestic or wild; be it a cat as a pet or birds outside ones window.  Research into the nature and merit of the human animal bond began in the late 1700s when, in York, England, the Society of Friends established the The Retreat to provide humane treatment for the mentally ill.  By having patients care for the many farm animals on the estate, society officials theorized that the combination of animal contact plus productive work would facilitate the patients rehabilitation.  In the 1870s in Paris, a French surgeon had patients with neurological disorders ride horses.  The patients were found to have improved their motor control and balance and were less likely to suffer bouts of depression.
In the 19th century, in Bielefeld, Germany, epileptic patients were given the prescription to spend time each day taking care of cats and dogs.  The contact with the animals was found to reduce the occurrence of seizures.  In 1980, a team of scientists at the University of Pennsylvania found that human to animal contact was found to reduce the physiological characteristics of stress; specifically, lowered levels of blood pressure, heart rate, respiratory rate, anxiety, and tension were all found to correlate positively with human pet bonding.
Historically, animals were domesticated for functional use; for example, dogs for herding and tracking, and cats for killing mice or rats.  Today, in Western societies, their function is primarily a bonding function.  For example, current studies show that 60-80% of dogs sleep with their owners at night in the bedroom, either in or on the bed.  Moreover, in the past the majority of cats were kept outside (barn cats) whereas today most cats are kept indoors (housecats) and considered part of the family.  Presently, in the US, for example, 1.2 billion animals are kept as pets, primarily for bonding purposes.  In addition, as of 1995 there were over 30 research institutions looking into the potential benefits of the human animal bond.

# Debonding
In 1976, sociologist Diane Vaughan proposed an uncoupling theory, where, during the dynamics of relationship breakup, there exists "turning point", only noted in hindsight, followed by transition period in which one partner unconsciously knows the relationship is going to end, but holds on to it for an extended period, sometimes for a number of years.