A Thin Line Between Love And Hate… In Your Brain

We are all familiar with the fuzzy feelings that accompany falling in love. You and your partner become emotionally connected, supported, and complete. Although human love is a complicated and long journey, scientists consistently find that the release of a specific neuropetide—oxytocin—may kick start these feelings right away in courtship. In fact, for the past few decades researchers have referred to oxytocin as the “love hormone,” and credit its release as the glue that ties humans to their loved ones.

Oxytocin’s cupid effect is not specific to romantic love, but rather various forms of pro-sociality. Pregnancy and labor are times when a woman naturally experiences surges of oxytocin, which may facilitate mother-infant bonding. In males, administering oxytocin has been shown to increase trust, understanding, and even enhance empathy in males with social deficits. Nonetheless, oxytocin is best known for keeping us monogamous, or “pair bonded” as the scientists say.

But is oxytocin really the saccharine drizzled on social life? Recent findings suggest not. While oxytocin may enhance positive emotions and pro-sociality with the people we care about, it may also contribute to negative views and behaviors towards people to whom we are not close. Research in social psychology finds that humans simultaneously show favoritism for the people in their social circle (“ingroup”) and derogation of people in social groups that are different from their own (“outgroup”). Although not conclusive, recent findings suggest that administering oxytocin to males not only enhances their in-group favoritism, but in some cases, also increases defensiveness towards outgroup members.

Given the atrocities that can result from ethnocentricity, the suggestion that oxytocin could increase an ingroup bias calls into question whether oxytocin is really the brain’s warm and fuzzy cuddle chemical. When it comes to oxytocin, does a rose by any other name really smell as sweet?


Kosfeld, M., Heinrichs, M., Zak, P., Fischbacher, U., & Fehr, E. (2005). Oxytocin increases trust in humans Nature, 435 (7042), 673-676 DOI: 10.1038/nature03701

Bartz, J., Zaki, J., Bolger, N., Hollander, E., Ludwig, N., Kolevzon, A., & Ochsner, K. (2010). Oxytocin Selectively Improves Empathic Accuracy Psychological Science, 21 (10), 1426-1428 DOI: 10.1177/0956797610383439

De Dreu, C., Greer, L., Handgraaf, M., Shalvi, S., Van Kleef, G., Baas, M., Ten Velden, F., Van Dijk, E., & Feith, S. (2010). The Neuropeptide Oxytocin Regulates Parochial Altruism in Intergroup Conflict Among Humans Science, 328 (5984), 1408-1411 DOI: 10.1126/science.1189047

De Dreu, C., Greer, L., Van Kleef, G., Shalvi, S., & Handgraaf, M. (2011). Oxytocin promotes human ethnocentrism Proceedings of the National Academy of Sciences, 108 (4), 1262-1266 DOI: 10.1073/pnas.1015316108

  • I think that the same way that maternal bonding is the archetypal pro-social behavior in mammals, maternal anti-bonding is the archetypal anti-social behavior.

    Maternal anti-bonding is not well studied, and especially not in humans. It is what happens in the postpartum period when mothers are put under extreme stress. Essentially all mammals will kill their infants under sufficient stress. It is necessary for mammals to have such a trait because lactation is so energy intensive. If the mother cannot obtain sufficient calorie resources to sustain her infant until it is weaned, then she is better off killing it, and sooner rather than later.

    If the chain of feeding sufficient calories to the infant to sustain it is broken, the infant dies and that reproductive event has failed. The only way to then have a successful reproductive event is to start over. The earliest stages of reproduction are not very calorie intensive. It is the latter stages, where the infant is large and using calories for growth that calorie demands are the highest.

    If the chain is going to break, better to break it first so a new chain can be started sooner.

    The paper you cite makes perfect sense in this context, where resource limitations change the scope of the in-group and out-group. If resources are limited enough, then to a starving mother, even her infant can become a member of an out-group.

    I think that it is nitric oxide that regulates the various parameters of the in-group and out-group with high NO fostering a large and inclusive in-group and low NO fostering the opposite. I have a post on my blog about xenophobia and about acute psychosis leading to infanticide. To a sufficiently stressed out mother, her autistic child can become a member of the out-group. Sort of like the changelings of another time.

    • Naomi Radunski

      Our behaviour is not ONLY chemical in origin … your comments, though informative, give that impression. Nothers who, though starving to death, will try to feed their babies until they themselves fall down and die. Multitudes of such instances recorded in Africa. Mothers who, on the way to their own deaths in the gas chambers, hid their babies under their clothes so as not to die with them. These are not the behaviours of people who ‘under extreme stress’ give up their children. And children can sometimes be very trying and parents sometimes say, ‘God, I’d like to throttle her/him’ – but the same parent would lay down their life for their child. Sorry, but there aren’t over 6 billion people on this planet because mothers give in under stress and kill or abandon their children … on the contrary. So perhaps it would be more balanced to suggest that, depending on how we have experienced and observed stress management in our own environment – familial and societal; and depending on the origin, nature and level of the stressors – in other words, depending on a huge range of influences – some mothers might, very, very rarely, kill their children.

  • May I suggest a further resources to learn more about empathy and compassion.
    The Center for Building a Culture of Empathy
    The Culture of Empathy website is the largest internet portal for resources and information about the values of empathy and compassion. It contains articles, conferences, definitions, experts, history, interviews,  videos, science and much more about empathy and compassion.

    I posted a link to your article in our
    Empathy and Compassion Magazine
    The latest news about empathy and compassion from around the world

    • Anonymous

      The empathy website looks great!–thanks for linking this article to it!

  • Naomi Radunski

    Proof reading error, third sentence; the word is NEUROPEPTIDE. This sort of slip immediately affects the credibility of a ‘scientific’ piece. Recommend proof reading on hard copy – one unconsciously ‘skps’ (sic) more when reading on screen. Cheerio.

  • onergk69

    I am fascinated by the underlying mechanisms re: love/hate, also referred to as “ambivalence”. Sometimes referred to as “the 2 faces of intimacy”.

    Persons who introject “secure” attachment can typically integrate these opposing “twin” emotional states. Those w/ “insecure” attachment have difficulty integrating it. Those w/ “disorganized” attachments cannot. Prime example are those exhibiting borderline personality.

    And almost every human quality is best understood from a biopsychosocial (spiritual) frame.


  • Hello, my name is George and I am psicologo Barcelona. I think oxytocin may explain some of our behavior, but how do we know if our behavior depends on the oxytocin or oxitacina depends on our behavior. That is, as the article says, there is a relationship between a particular chemical and a certain emotion. But we know that emotions are those that depend on the chemistry and the chemistry is not dependent on emotions?
    Sorry for my English.

Meghan Meyer, PhD (c)

Meghan Meyer, PhD candidate, studies social cognitive neuroscience at University of California-Los Angeles. Prior to joining UCLA, she worked on behavioral and brain imaging studies in the Stanford University Cognitive and Systems Neuroscience Lab and the Social Cognitive Neuroscience Lab at the University of Chicago, and completed her M.A. in cognitive science, with a specialty in cognitive neuroscience, from Ecole Normale Superieur, in Paris, France. When she is not in the lab designing studies and analyzing data, she enjoys writing about scientific findings and their broader impact for general audiences.

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