Here are some highlights from this 2013 book:
* Oxytocin appears to alter the dopaminergic response of mammals to their own infants, tipping the balance from avoidance to approach.
It has been suggested that oxytocin is a love drug or a trust hormone, but I prefer to think of oxytocin as the nurse neuropeptide.
* Oxytocin turns the rest of us from zeros to heroes when it comes to caring for our own children. Nurses do it for everyone every day.
In animals, prosocial sentiments toward one’s offspring have been associated with higher levels of oxytocin modulating reward responses in the ventral striatum and ventral tegmental areas of the brain—both part of the reward system. One account suggests that oxytocin released in the ventral tegmental area leads to the release of dopamine in the ventral striatum region associated with increasing our motivation to seek out a reward. Fearlessness appears to be influenced by oxytocin interactions within the septal region, adjacent to the ventral striatum. Both oxytocin and the septal region of the brain are involved in diminishing the physiological indicators of distress, which may facilitate helping someone else even when the situation is distressing or gross. In other words, when we see someone in need, say, someone with a bloody wound, oxytocin may simultaneously increase the reward value of approaching that person and decrease the distress we might have over being near someone else in distress.
Although there are great similarities in how oxytocin promotes care for offspring across mammalian species, oxytocin has different effects on how primates and nonprimates treat strangers. In nonprimates, increased oxytocin is associated with increased aggression toward strangers. This is generally understood in terms of mothers’ protecting their infants from unknown threats. A mother sheep will attack an unrelated baby lamb that tries to nurse from her. But when the oxytocin processes are blocked, the mother sheep will allow the unrelated lamb to nurse. Thus, in nonprimates, oxytocin promotes direct care of one’s own offspring, including protecting them against others. This ensures that the mother’s limited resources are spent only on those offspring that will pass on her genes to future generations.
Both the caring- and aggression-related effects of oxytocin have been demonstrated in humans as well. Administering oxytocin has been shown to increase generosity when people play behavioral economics games like the Prisoner’s Dilemma. On the flip side, psychologist Carsten De Dreu in the Netherlands has demonstrated in multiple studies that administering oxytocin leads to more aggressive responses to members of other ethnic groups in the Prisoner’s Dilemma.
While oxytocin can promote ingroup favoritism (that is, toward groups that one is a part of) and hostility toward those who are not part of one’s ingroup, the dividing line between friend or foe differs in a crucial way between primates and other mammals. In nonpri-mates, oxytocin leads individuals to see all outsiders as possible threats, thus enhancing aggression toward them. In contrast, humans divide others into at least three categories: members of liked groups, groups, members of disliked groups, and strangers whose group affiliations are unknown. Administering oxytocin in humans facilitates caregiving toward both liked group members and strangers , but it promotes hostility toward members of disliked groups.
Oxytocin in humans helps to promote altruistic tendencies not toward one’s own group—because that isn’t altruism in the strongest sense of the word—and not toward members of disliked groups. But oxytocin can increase our generosity toward complete strangers, which is quite magical, as strangers who start with a positive bias toward one another can do great things together, such as building houses, schools, and other institutions that support a society.
* The severing of a social bond —whether it’s the end of a long-term romantic relationship or the death of a loved one—is one of the greatest risk factors for depression and anxiety. Although adults can survive with unmet social needs far longer than with unmet physical needs, our social bonds are linked to how long we live. Having a poor social network is literally as bad for your health as smoking two packs of a cigarettes a day.
The social motivation for connection is present in all of us from infancy. It is a pressing need, with a capital N . The evolutionary fallout from the presence of these social needs is a major advantage to those who are able to minimize their social pains and maximize their social pleasures. Building and maintaining social networks is no easy feat. Just watch any reality show, from Survivor to MTV’s Real World . Fortunately, evolution has given us not one but two brain networks that help us to understand those around us and to work more cohesively with them. Connection is the foundation on which our social lives are founded, but evolution was far from finished, making sure we would make the most of our social lives.