Oxytocin Is Not Always Kind. It Can Evoke Disgust.


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Oxytocin, the so-called love hormone, mediates bonding such as during mother-infant or human-dog interactions. It turns the brain into a pro-social mode by tuning down the amygdala (fear and disgust centre) and exciting the dorsal striatum (trust and reward centre).

“It makes people more trusting, forgiving, empathic and charitable,” Robert Sapolsky, a multi-award-winning author and professor of biology, neurology, neurological sciences, and, by courtesy, neurosurgery, wrote in a 2018 review. “It improves the accuracy of reading people’s emotions.”

Probing further, scientists discovered the pro-social effects of oxytocin only apply if the person is one of us  or an in-group member. If the person is one of them  or an out-group member, oxytocin becomes anti-social.

“In such settings, the [oxytocin] hormone decreases trust, and enhances envy and gloating for the successes and failures, respectively, of the out-group member,” Professor Sapolsky continued. “Moreover, the hormone makes people more pre-emptively aggressive to out-group members, and enhances unconscious biases toward them.”

So Oxytocin has a binary role in pro- and anti-social. What segregates in-group and out-group? Anything that can be classified as one of us or one of them, be it race, religion, political beliefs, pets, spouses, or children. Here are some experiments illustrating the binary role of oxytocin:

  • Intranasal oxytocin increased the emphatic neural responses of Chinese males on Asian faces, but not Caucasian’s, compared to placebo.
  • Intranasal oxytocin made humans more cooperative in a trust game provided they had prior friendly interactions (becoming in-groups). Playing the game with an anonymous person (an out-group member) did not influence, or even lowered, cooperativity compared to placebo.
  • In a Prisoner’s dilemma game, intranasal oxytocin did not make in-group members more distrusting toward out-group members. If the out-group members posed a threat, however, in-group members behaved much more uncooperatively and aggressively compared to placebo.
  • In an economic game, intranasal oxytocin enhanced extreme lying and speed of dishonest decision making if it serves the in-group at the expense of the out-group.
  • In a game of chance with an anonymous player (an outgroup), intranasal oxytocin increased envy (if participants lost more money) and gloating (if participants gained more money) compared to placebo.

“The [oxytocin] circuitry may have evolved to sustain within-group cooperation, ingroup protection, and if needed, competition towards rivalling outgroups,” Carsten de Dreu, a professor of psychology and behavioural economics, wrote in a 2012 paper reviewing some of the listed studies.

If there’s competition, oxytocin evokes distrust, envy, gloat, and disgust. Brain imaging showed that the cortical-amygdala and insular cortex mediate this competition. These are brain circuits involve in disgust. “A basic role of oxytocin may be to increase vigilance, defensive aggression, coupled with the expression of disgust associated behaviours, to protect oneself and in‐group members against the out‐group threat,” Martin Kavaliers, a professor of psychology and neuroscience, and co-workers wrote in a 2018 review titled “Social Neuroscience fo Disgust.”

So oxytocin is not always kind and loving if competition is involved, especially at the expense of in-group members or one of us. “In other words, a hormone [oxytocin] touted for its capacity to enhance pro-sociality does no such thing,” Professor Sapolsky explained. “Instead, what it does is worsen Us/Them dichotomies, enhancing in-group parochialism as well as out-group xenophobia. This is certainly not the hormone to cure our ills.”

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