And the Two Become One: The Body Expresses the Person Through The Biochemistry of Unity & Indissolubility by Dianne S. Dewane

In America’s relativistic culture, where tolerance is touted as a primary ideal, it is not popular to propose ontological truth that is a specific design in a particular creation. There is no room for norms that dictate right and wrong behavior, especially when it comes to decisions about one’s “personal” life. Indeed, in regard to sexual intercourse, there is a flat out refusal to acknowledge that it may have a specific value and a singular context. The Catholic Church has been viewed unpopularly by many Americans, therefore, for its steadfast teaching that sexual intercourse is an expression of conjugal love that has both procreative and unitive dimensions that belong only within the context of indissoluble marriage. Large portions of contemporary American culture, however, vehemently maintain that sex has different values for different people and that the context of sex acceptably ranges from expressions of love to casual recreation. A study of the human biochemistry associated with sexual intercourse, however, reveals that there is nothing casual about human sexuality. Indeed the delicate biochemistry of the human person is designed and ordered to respond to intercourse by forming exclusive, intimate, stable, pair-bonds that favor permanency.

Pope John Paul II’s Theology of the Body teaches that unity and indissolubility are “normative” for the one-flesh union.[1] They are normative because they speak of the attributes built into our creation and the original design of the experience of the one-flesh union. These can be applied universally since they are written into our very being, and are certainly not called normative due to imposed extrinsic laws based on a consensus or majority opinion. Christ himself when questioned on this matter referred twice to “the beginning”[2], adding that what God has joined “no man should put asunder.”[3] “The beginning” refers to how it was meant to be and how it was experienced in man’s original state before sin came into the picture. Christ affirms that the one-flesh union, entered into by free will, is not to be dissolved, but that the unity of the two should be maintained.

Though this unity and indissolubility of marriage may seem theoretically ideal perhaps, yet grossly unrealistic and maybe even unappealing to contemporary culture, scientific research is beginning to uncover that the physiology of the person may actually be ordered to it. Sexual intercourse appears to be a threshold at which man and woman enter into a new relationship that is biochemically oriented toward staying together, geared toward their unity as a couple. Chemicals released during intercourse, such as oxytocin and vasopressin, introduce a unique effect that promotes a series of pair-bonding behaviors.[4] Furthermore, this primary exposure of the system to these chemicals seems to trigger a response that permanently alters body chemistry, and consequently behavior tendencies, making the pair more receptive towards their partner.[5] Once the bonds are established, the disruption of these bonds causes great distress.[6] It is clear that the body favors the maintenance of these bonds and reacts unfavorably when they are broken. In displaying such responses, it appears that the biochemistry of the body associated with sexual union is optimally designed to be experienced within the context of an intimate and permanent relationship.

The information supporting this claim stems from research done on the prairie vole (Microtus ochrogaster), a small rodent that lives in the grasses of the Midwest. The research began when field scientists discovered that the prairie vole displayed monogamous behavior in contrast to its relative, the montane vole (Microtus montanus), which showed the more typical patterns of non-monogamous behavior.[7] The prairie vole was noted as showing partner-preference, selective aggression toward unfamiliar members of the same sex, and biparental care of the young, all typical of indications of monogamy. The montane vole, however, showed classic non-monogamous behaviors, such as no partner-preference, little aggression toward other prospective mates for a past partner, and the care of the young was left to the female.[8] A hormone produced in mammalian brains called oxytocin was already known to promote bonding in some species between males and females, as well as between mothers and offspring. The researchers wondered, then, if oxytocin might play a role in the affiliative behaviors of the prairie vole.

The studies conducted discovered that indeed oxytocin plays a critical role in pair-bond formation in monogamous mammals, though vasopressin was found to be most important in males. The female prairie vole, noted for her cuddling and affectionate grooming tendencies toward her chosen mate, when given an extra dose of oxytocin, increased her affections and stuck even tighter with her partner. Conversely, when an inhibitor to oxytocin was introduced to her system, she left her partner for others, ceasing to display a preference at all. The oxytocin antagonist prevented pair bonding, though it did not interfere with mating.[9] In males, it was not oxytocin, but vasopressin that was found to play the key role in pair-bonding. Actually, it was found that when additional vasopressin was administered to the male, his normal behavior of mate guarding was amplified into an aggressive snarling behavior to other passerby males. When the vasopressin antagonists were introduced, the protective male casually stepped aside, allowing other males the opportunity to mate with his partner.[10] In addition to selective aggression, vasopressin has been shown to be active in social recognition of mate and pups.[11] The stark contrast in behavior patterns between the two types of rodents left scientists wondering what accounted for the difference. The scientists concluded that the neuropeptides oxytocin and vasopressin must be used differently in the prairie and montane voles since the hormones were present in each animal, yet showed such pronounced effects only in the monogamous prairie vole.

Researchers then turned their attention to where in the brain the receptors for these neurotransmitters were located, hoping that would provide some answers. Oxytocin receptors were found in high concentration in the nucleus accumbens and the pre-limbic cortex in prairie voles. These regions of the brain participate in the mesolimbic dopamine pathway, which functions in a pattern of reinforcement and behavior reward. This means that the release of oxytocin stimulates the nucleus accumbens, which then triggers the reward pathway that allows for conditioning and learning. It is this pathway that is initiated by the release of oxytocin after mating, which then promotes mate recognition through this reinforcement pattern. Montane voles did not prove to have the same receptor distribution pattern at all, exhibiting a sparse number of receptors in the nucleus accumbens. Not enough receptors are located there to actually stimulate the mesolimbic dopamine pathway, and as a result, partner recognition is not learned. Vasopressin receptors are found in large numbers in the ventral forebrain of the prairie vole in the ventral pallidum.[12] This area of the brain is likewise associated with the reward pathway and contributes to the male’s ability to recognize his partner. Again, the montane vole does not express a high density of these receptors in that area, and thus when vasopressin is released it is not able to stimulate the ventral pallidum to trigger the system for partner recognition and bonding does not occur. This distinction of two different patterns of receptor distribution within the brain thus allows researchers the ability to identify monogamous and non-monogamous species based on this information.[13]

Because humans share the same receptor distribution patterns as the prairie vole, researchers hope that studies done on them might provide insight into human social behavior patterns, as well. The literature has long shown that oxytocin is released in large quantities during childbirth (to aid in the contractions of the uterus) and in the milk let down response of nursing.[14] More recent studies, however, have focused on oxytocin that is released during sexual arousal and intercourse and its effect of social bonding.[15] It is proposed that oxytocin is released in a variety of ways and in different amounts. Along with childbirth and nursing, the third event that can trigger an enormous release of oxytocin is sexual climax – and such a release occurs in both the man and woman and is thought to be associated with contributing to the pleasure sensation and intense emotional pair-bonding.[16] The studies involving the prairie vole also showed that after mating, oxytocin played a particular role in females in inducing cuddling and affiliative behaviors.[17] Such effects in women have long been noted through human experience, as well. Scientists point to oxytocin’s partnership with estrogen as an explanation of the heightened susceptibility of women to its effects of intense bonding and also significant distress when bonds are broken.[18]

In addition to climax, however, oxytocin has been found to be released in smaller doses through general sexual arousal by vaginal and cervical stimulation,[19] and through touch and warm temperature.[20] Some of the noted effects of oxytocin include potent physiological anti-stress and anti-anxiety effects,[21] long-term lowering of blood pressure, and even increasing the rate at which wounds heal.[22] Because oxytocin is released in response to social stimuli, researchers believe it must play a role as part of a neuroendocrine substrate underlying positive social experiences. This, in addition to the fact that oxytocin can be conditioned to accompany a psychological state or imagery, may help explain some of the health-promoting effects of some alternative therapies such as hypnosis and meditation.[23] Oxytocin appears to be so important that an absence of exposure to it as a child has been linked to problems in emotional developmental.[24]

Vasopressin, which is released in both men and women as a normal part of kidney function and water regulation, is specifically linked to pair-bonding in males after its release associated with intercourse. Studies have established that there is a rapid development of both selective aggression and partner preferences following mating, which are two critical functions in monogamous pair bonding in that they help maintain the boundaries of exclusivity for the couple.[25] This chemical plays an important role in prompting a desire of the male to stay with his partner rather than roaming to find another. Additionally, it has been shown that vasopressin contributes to whether or not males contribute to rearing offspring.[26] Other studies have demonstrated the value of this neuropeptide in social recognition, though it had no effect on object recognition. This is an important factor in paternal investment and bonding as it produces biochemical links between the male and his offspring.[27] Essentially, vasopressin released after intercourse is significant in that it creates a desire in the male to stay with his mate, inspires a protective sense (in humans almost a jealous tendency) about his mate, and drives him to protect his territory and his offspring. The value of such tendencies toward the maintenance of marriage and family can easily be anticipated.

The more researchers learn about the neuopeptides oxytocin and vasopressin, which are both significant hormones released through sexual intercourse, the more undeniable it becomes that the human body is oriented toward forming lasting and intimate bonds with the sexual partner. The hard wiring of the human brain has a circuit for lust as well as a circuit for love responses, but what is notable is that behavior that triggers the love circuitry actually promotes physical health, well-being and positive psychological effects. Conversely behavior that triggers the lust pathway results in physiological effects that are grating on the physical, emotional, and psychological dimensions of the person. Behavior that triggers the love pathway includes the maintenance of exclusivity and intimacy of sexual bonds. Loving marital union exemplifies such behavior in that it provides a stable, permanent context for the intimacy. Behavior that triggers the lust pathway, however, include those actions that respond to various stimuli, such as attraction or desire, but that are outside the context of an exclusive and intimate relationship, where desertion or lack of emotional engagement of partners is more common. Pre-marital sex and co-habitation are two examples of behavior that sociologists and psychologists have shown to produce negative long-term feelings and psychological responses. It makes sense, in light of the biochemistry of bonding that comes through sexual intimacy, that the lack of constancy, commitment, and regard for the partner is internalized through increased experiences of depression, dissatisfaction, and the disruption of future bonding potential.[28] Such a discrepancy in the response of the person to the two different options – love and lust – indicates that it is in the subject’s best interest - naturally – to choose behavior that is truly loving and respectful of the dignity that each person deserves.

The Theology of the Body teaches that the nuptial meaning of the body refers to its capacity to express love. Because the body expresses the person - in a certain sense making visible what is invisible, the body has the capacity to be a gift of the self to another in a real way. In this way, the giving of the body in sexual intercourse is intrinsically linked with the giving of the self in love. Love is shared in the free giving of the self and receiving of the other, and it is this free gift of love that fulfills a person. It seems plausible that the positive physiological, emotional, and psychological effects related to exclusive and permanent sexual pair-bonding, in a sense, expresses such fulfillment in a physical way.

Interestingly enough, recent scientific findings suggest that tenderness expressed in physical, non-sexual affectionate touching is a bio-chemical condition for optimal sexual experience. The part of the brain that is responsible for producing the feeling of euphoria felt after drinking alcohol, doing drugs, or having sexual intercourse is also prone to building up tolerance to these effects, due to its participation in the mesolimbic pathway. Such tolerance drives individuals to drink more or do more drugs to achieve the same effect as previously experienced. Likewise, such an effect prompts some individuals to seek ways to spice up their sex lives by trying non-traditional positions, new or multiple partners, or other alterations that shift the focus of sex from love to pleasure in hope of attaining that same high again. However, females who readily have oxytocin available in their system (released by frequent positive person-to-person touching) are actually able to counter this tolerance mechanism naturally.[29] This seems to indicate that the body is designed to be affectionately touched on a regular basis. Under the conditions of loving, regular touch – whether it is through holding hands, hugging, or cuddling – the body responds optimally to more intimate sexual expressions. Sex on a physical level, it would appear, is thus ordered toward tenderness, an important aspect of authentic love that contributes to closeness between a couple, as well as the maintenance of exclusive permanency.

John Paul II refers to the hermeneutics of the gift as a means of understanding creation as “given” to the extent that it was called into being from nothingness. Appreciating the free gift of creation from God helps put into perspective the free gift human love ought to be. Because God did not need to create, the fact that he did is both gratuitous and mysterious, seemingly to spring from an unmerited, spontaneous love simply for the sake of the other. Creation appears then to be “given” to itself. Man has an interior dimension of the gift that he becomes conscious of in different ways. One of the most profound ways in which one perceives the gift of creation is when he or she is presented with the “other”. In the second account of Genesis, Adam exclaims “At last, this one is bone of my bones and flesh of my flesh!”[30], an exclamation that denotes his profound joy at the other who is both “helper” and “fit for him”.[31] This hermeneutic is indispensable for an adequate anthropology because the nuptial meaning of the body allows man and woman to make free gifts of themselves to each other in conjugal love, in a sense recapitulating the act of the Creator.

Giving, however, implies a permanency in that gifts are unilaterally offered with no expectation to reclaim the gift at some point. In human terms, in the gift of self there necessarily needs to be an implication – and an outward sign – that the individuals are offering themselves to the other, not in a temporary way that uses, but in a permanent way. Marriage is the term given to such conditions recognized by society, when man and woman make the free choice to give themselves to the other in a permanent, loving way. The love of parents offered in the gift of themselves to their spouse in conjugal relations has the capacity to participate in creation through the blessing of fertility. Children enter the world as the fruit of their parents’ freely given love, just as creation itself came to be through God’s gratuitous gift of love. In this way the blessing of fertility connected to conjugal love further recapitulates creation in that a new being comes about through the freely given love and gift of self by the parents.

Another reason why the Church believes in the marriage and family model of authentic love relationships is that they are the sacramental sign on earth of the heavenly relationship of the trinity. Theology of the Body also teaches that,

This statement is significant to marriage because it puts marriage in a unique and privileged place as the venue through which man becomes imago trinitatis. Although man and woman image God in their individuality, they are able to image Him even more fully in their dual unity, as male and female because the two sexes encompass the complementary aspects of humanity. Furthermore, they most fully image God in the communion of persons, where in the free gift of self, love flows out to create anew like the trinity itself, where the love of the Father and the Son send forth the Holy Spirit. Marriage is thus the fundamental form of human relation that gives witness to the fruitfulness or fecundity of love.

In original solitude, man (in the general sense) becomes aware that he is different from the animals - he is alone in the world, unlike the others. In being given the command to name the animals and have dominion over them, he increases his self-knowledge and self-consciousness that he has capacity for rationality and superiority over the animals. This growing interior knowledge of his “self” and his subjectivity increasingly separates him from the rest of creation. This realization opens him up to and causes him to long for relationship with an “other” because he desires to be with another of his kind. God himself said it was not good for man to be alone, that he should have a suitable helpmate. Thus when woman is created and presented to him, he joyfully recognizes her as a partner for him, and her revelation of herself makes him even more conscious of himself and of his body. The two are gifts to each other, helping them to know themselves in coming to know each other. That man (again, general sense) should not be alone is telling of the fullness that is present to a communion of persons. Not only should he have another at his side, but he should also have someone that complements him. Such a person is different enough to draw him out of himself and make him more than he already is. That is precisely what a communion of persons is capable of achieving.

In his Theology of the Body, John Paul II also teaches that the human body in its maleness or femaleness was created in a duality that was meant for communion. In that way, the body, in its openness to the other, expresses that the person is apt, or made, for love to be shared with another. Neither man nor woman needs union with the other for survival, yet they desire to be in communion with the other, to give themselves to each other in order to forgo singular existence and participate in a relationship with the other. In that giving and communing, at all levels of the person both visible and invisible, Catholic theology teaches that the “two become one”.[32] Even the biochemistry of the human person indicates that when a couple reaches the point of ultimate physical communion in sexual intercourse, the union is apt for tenderness and permanence. It seems that all orders of creation work in harmony to promote the design intended by the Creator.

Marriage as a communion of persons serves to make manifest the recapitulation of creation, and humanity’s special role as co-creator with God. Reflection on creation out of nothingness and the fact that God did not need to create, but did so anyway, highlights the gift-quality of creation. In this sense, God chose to freely give the world to itself in love for its own sake. Likewise, a communion of persons is formed when the man and woman involved heed the nuptial meaning of their bodies and make free gifts of themselves to each other out of love, loving each other truly for the other’s sake only. In doing so, they follow the interior design of love stamped in each person and participate in the freedom of the gift. It is in marriage that conjugal love can make a complete gift of self in the one-flesh union, and is therefore unique in its potential to further recapitulate creation by bringing new life into existence through the gift of love.

Because marriage serves as a visible sign of an invisible truth, it is considered sacramental in its nature. While solitary man is capable of manifesting imago dei, there is a fullness of God not yet expressed in a single individual. Indeed, even in the companionship of friends one must admit there is an aspect of God that is not given expression. The physical communion of persons requires more from the human relationship than solitude or friendship alone can afford. Not only is solitude overcome in marriage by the bringing together of the dual unity of persons, but in the one-flesh union the communion of persons is made manifest. In this way, marriage is the sacramental sign of imago trinitatis. Indeed the physical manifestation of the communion of persons and the fecundity of love speak to the mystery of creation and the love of God for his creation.

John Paul II is affirming the existential priority of the person as such over the sexually differentiated man or woman. This is not to say that being male or being female is insignificant, rather the Holy Father is highlighting the immensity of our personhood in creation. Indeed, the Pope states repeatedly in his Theology of the Body that the somatic constitution of being male or female forms the person from the inside out. However, there is a certain sense in which personhood must “precede” sexual identity not chronologically, but existentially. This makes sense in that gender is noted in the animals, but it is our subjectivity as persons that defines us as insurmountably different from the rest of creation and allows us to have nuptial bodies.

The human body expresses the person by making visible what is invisible. It is a sign that has meaning in itself and points to what is beyond it. Animal bodies engage in action driven by instinct and reaction rather than choosing their actions. The human subject’s body, however, responds to the freely determined will of the person and acts according to its interior motivations and decisions. The physical body then responds in an objective way, but it is the choosing that separates animals and humans in this respect. This means that a person can be expressed in a way that promotes both the interior and exterior dimensions of the person. It is important to remember how unique this is. The body is not a puppet of nature, but an acting part of the subject. Before the body expresses maleness or femaleness, however, it expresses a personal subject. This is why it can be said that in the first instance the human body, because of its fundamental ability to express the interior person or subjective being, has primary significance, and in the second instance the body is significant in so far as it is constituted male or female and accordingly expresses these two ways of being an embodied person.

Additionally, the nuptial meaning of the body expresses love, a unique ability of the body of a personal subject. As the interior person desires to make a gift of oneself in love to another, the body is able to manifest such a gift externally. This is a paramount difference between animals and persons, in that animals come together by drive alone, whereas persons experience a desire for the other and have the cognitive ability to make a choice to enter into relations with the other or not. If they choose to enter into relations, the choice is freely determined. In this way, people are able to respond to what John Paul II calls the freedom of the gift.

While male and female embodiment is formative to the individual, it is clear that the distinction of the human body from that of animals is greater than the distinction of the bodies of the two sexes. The variance in the embodied genders allows the same truth of human love to be expressed differently, but it remains that both expressions speak of the same singular truth of the mystery of human love. These two expressions are certainly complementary in nature and provide a certain fullness, yet they are decidedly expressive of the same unique subjectivity. Endowed with unique gifts that allow the body to be a privileged place of expression in response to the interior person, the human body therefore belongs more deeply to the structure of the personal subject than to the fact of the somatic constitution as male or female.

While history has witnessed various moments of differing acceptability for sexual norms, by and large there has been a general default to placing sexual intercourse in the context of marriage as a means for the couple to bear a family and express intimacy. Today, however, with the advancement of technology and relaxed social factors, no such default seems necessary and sex has become common with teenagers, unmarried adults, and extra-marital affairs as anything from expressions of progressing love and intimacy to casual recreation. Historically, social consequences of taking intercourse out of that context led to embarrassing out-of-wedlock births, the ruin of social reputation - especially among unmarried girls, and a general sense of shame that was shared by the perpetrators, their families and sometimes associates. However, at this moment in history, the factors that surround the issue are geared to minimizing the consequences of sex outside of marriage. Technological advancements have allowed for a great separation of fertility from intercourse, making it conveniently sterile for those who would prefer not to have to consider the possibility of raising a family with their bed partner. Certain streams of feminism and other liberal groups rally for sexual permissiveness and promiscuity to be more acceptable, claiming it to be more natural to avoid such socially constructed institutions as marriage. As long as the world turns, there will probably be an ongoing debate about the purpose and meaning of sex, but as far as human biochemistry is concerned, it has spoken – and it favors unity and indissolubility.

1. Pope John Paul II. Theology of the Body. (General audience Sept. 5, 1979).

2. The phrase “the beginning” is often used to refer to the story of Adam and Even in the book of Genesis. Here the reference is specifically made to Gen. 2:24.

4. Kendrick, KM. “Oxytocin, Motherhood and Bonding”. Experimental Physiology. Vol. 85, Spec No. (Mar 2000), pp. 11S-124S.

5. Sinha, Gunjan. “You Dirty Vole”. Popular Science. Vol. 261, no.6 (Dec 2002 ).

6. Carter CS. “Neuroendocrine Perspectives on Social Attachment and Love”. Psychoneuroendocrinology. Vol. 23, no. 8 (Nov 1998), pp. 779-818.

7. Sinha, Gunjan. “You Dirty Vole”. Popular Science. Vol. 261, no.6 (Dec 2002 ).

8. Anderson-Hunt M and Dennerstein L. “Oxytocin and Female Sexuality”. Gynecologic & Obstetric Investigations. Vol. 40, no. 4 (1995), pp. 217-21. Carter CS, Williams JR, Witt DM, and Insel TR. “Oxytocin and Social Bonding”. Annals of the New York Academy of Science. Vol. 12, no. 652 (Jun 12 1992), pp. 204-11.

9. Insel TR, Winslow JT, Wang ZX, Young L, and Hulihan TJ. “Oxytocin and the Molecular Basis for Monogamy”. Advanced Experiments in Medical Biology. Vol. 395 (1995), pp. 227-34.

10. Sinha, Gunjan. “You Dirty Vole”. Popular Science. Vol. 261, no.6 (Dec 2002 ).

11. Everts HG and Koolhaas JM. “Lateral Septal Vasopressin in Rats: Role in Social and Object Recognition?”. Brain Research. Vol. 760, no. (1-2) (Jun 20, 1997) pp. 1-7.

12. Young LJ, Wang Z, and Insel TR. “Neuroendocrine Basis of Monogamy”. Trends in Neuroscience. Vol. 21, no. 2 (Feb 1998), pp. 71-5.

13. Insel TR, Winslow JT, Wang ZX, Young L, and Hulihan TJ. “Oxytocin and the Molecular Basis for Monogamy”. Advanced Experiments in Medical Biology. Vol. 395 (1995), pp. 227-34.

14. Gimpl G and Fahrenholz F. “The Oxytocin Receptor System: Structure, Function, and Regulation”. Physiology Review. Vol. 81, no. 2 (Apr 2001), pp. 629-83.

15. Carter CS, Williams JR, Witt DM, and Insel TR. “Oxytocin and Social Bonding”. Annals of the New York Academy of Science. Vol. 652 (Jun 1992), pp. 204-11.

16. Keroack EJ and Diggs JR. “Bonding Imperative”. Abstinence Clearinghouse. Article from the Medical Abstinence Council.

17. Sinha, Gunjan. “You Dirty Vole”. Popular Science. Vol. 261, no.6 (Dec 2002 ).

18. “Neural Oxytocin Systems as Genomic Targets for Hormones and as Modulators of Hormone-Dependant Behaviors”. Rockefeller University, NY. 1999.

19. Kendrick, KM. “Oxytocin, Motherhood and Bonding”. Experimental Physiology. Vol. 85, Spec No. (Mar 2000), pp. 11S-124S.

20. Uvnas-Moberg K. “Oxytocin May Mediate the Benefits of Positive Social Interaction and Emotions”. Psychoneuroendocrinology. Vol. 23, no. 8 (Nov 1998), pp. 819-35.

21. Uvnas-Moberg K, Bjokstrand E, Hillegaart V, and Ahlenius S. “Ocytocin as a Possible Mediator of SSRI-Induced Anti-depressant Effects”. Psychopharmacology (Berlin). Vol. 142, no. 1 (Feb 1999), pp. 95-101.

22. Uvnas-Moberg K. “Oxytocin May Mediate the Benefits of Positive Social Interaction and Emotions”. Psychoneuroendocrinology. Vol. 23, no. 8 (Nov 1998), pp. 819-35.

24. Winslow JT, Hearn ER, Ferguson J, Young LJ, Matzuk MM, and Insel TR. “Infant Vocalization, Adult Aggression, and Fear Behavior of an Oxytocin Null Mutant Mouse”. Hormonal Behavior. Vol. 37, no. 2 (Mar 2000), pp. 145-55.

25. Winslow JT, Hastins N, Carter CS, Harbaugh CR, and Insel TR. “A Role for Central Vasopressin in Pair Bonding in Monogamous Prairie Voles”. Nature. Vol. 365, no. 6446, (Oct 7 1993), pp. 545-8.

26. Wang Z, Young LJ, De Vries GJ, and Insel TR. “Voles and Vasopressin: A Review of Molecular, Cellular, and Behavioral Studies of Pair Bonding and Paternal Behaviors”. Progress in Brain Research. Vol. 119 (1998), pp. 483-99.

27. Everts HG and Koolhas JM. “Lateral Septal Vasopressin in Rats: Role in Social and Object Recognition?”. Brain Research. Vol. 760, nos. 1-2, (Jun 20 1997), pp. 1-7.

28. Nock, SL. “Comparison of Marriages and Cohabiting Relationships.” Journal of Family Issues. Vol. 16. no. 1.

29. McLean Hospital , Harvard Medical School. “Role of Oxytocin in the Neuroadaptation to Drugs of Abuse”. Psychoneuroendocrinology. Vol. 19, no. 1, (1994), pp. 85-117.