TED Talk: Oxytocin—the moral molecule

In this TED talk Dr. Paul Zak, a professor at Claremont Graduate University in Southern California, describes how oxytocin is responsible for empathy and why it is the “moral molecule” in humans.

I was intrigued by the title of this talk because I had always thought morality was something you learn and are not born with. What an interesting question; is it possible to have a biological tendency for morality?

Oxytocin is a chemical found in both humans and animals. In humans, it influences social interaction behaviour and social information processing (Baumgartner et al. 2008). It turns out that oxytocin is also related to trust and trustworthiness (Zak et al. 2004, Kosfeld et al. 2005).

In the original study, a game involving money transfers between participants was used to study the level of oxytocin in participants that demonstrated trust or trustworthiness (Zak et al. 2004). All participants received $10 for showing-up and were assigned to be either Decision Maker 1 (DM-1) or Decision Maker 2 (DM-2). Participants do not communicate directly with each other and all interactions occur via the computer. At the start of the game, both DMs are told that whatever amount of money DM1 transfers to DM2 will be tripled into DM2’s account. DM2 will then have the option to send any amount of money back to DM1. The level of trust is measured by the amount of money DM1 sends to DM2, and the level of trustworthiness is represented by the amount of money DM2 sends back to DM1.

When DM2s received money, their oxytocin levels went up but there was no change in oxytocin levels in DM1s who gave money to DM2s (Zak et al. 2004, Zak et al. 2005). This means there is a positive relationship between oxytocin levels and being shown trust (Zak et al. 2004). However, oxytocin is not responsible for producing trust itself (Zak et al. 2005). Trustworthiness is also linked to oxytocin because the oxytocin response and the high level of trustworthiness disappear when DM2s don’t receive any money from DM1s (Zak et al. 2004).

But what happens when oxytocin levels are artificially increased?

Using the same money transfer game, researchers found that participants given oxytocin through a nose spray showed a more trusting behaviour (Kosfeld 2005); that is, DM1s given oxytocin transferred more money than DM1s given just a placebo. However, a similar effect on trustworthiness was not observed. DM2s given oxytocin did not show higher signs of trustworthiness (higher back transfers) compared to DM2s given a placebo. Oxytocin just helped participants overcome their avoidance of betrayal to take more social risks (Kosfeld 2005).

So oxytocin is linked to trust and trustworthiness, but does it promote empathy?

Empathy allows us to understand another’s state of mind and motivates action if others seem to be in need. Barraza et al. (2009) found participants who showed more empathic concern (sympathy, compassion) after watching an emotional video had higher levels of oxytocin. Empathetic participants were also the most generous in donating to charities. In another study participants given oxytocin intranasally were better at interpreting subtle social cues from the eyes and guess what the person in a photograph might be thinking or feeling at that moment, compared to participants given a placebo (Domes et al. 2007).

So oxytocin helps us interpret what others think and motivates us to help. But is it really the moral molecule?

Zak defines morality as based on generosity and trustworthiness. He goes as far as saying that empathy is the basis of morality. But is empathy a requirement for morality?

People who show autism spectrum conditions (ASC), which include the classical autism disorder and Asperger’s disorder, also lack empathy (Baron-Cohen 1995). If morality is rooted in empathy then would we expect those with ASC to act immorally or less morally?

But what is morality really; isn’t it just a relative set of principles in which there is no absolute standard? Doesn’t society determine what is moral based its own set of customs and values? One neuroscience study believes that the human moral mind is created based on both biological and cultural factors (Moll et al. 2005).

Perhaps it is not a cause and effect relationship between oxytocin and morality. However since oxytocin is related to generosity, trust, and trustworthiness, then maybe it just provides an additional motivation to be moral as well.

Oxytocin may not be a requirement for morality but it does help us connect to other people–that alone makes it a pretty powerful molecule.



Baron-Cohen, S. (1995). Mindblindness: an essay on autism and theory of mind. Boston: MIT Press/Bradford Books.

Barraza, J., & Zak, P. (2009). Empathy toward Strangers Triggers Oxytocin Release and Subsequent Generosity Annals of the New York Academy of Sciences, 1167 (1), 182-189 DOI: 10.1111/j.1749-6632.2009.04504.x

Baumgartner, T., Heinrichs, M., Vonlanthen, A., Fischbacher, U., & Fehr, E. (2008). Oxytocin Shapes the Neural Circuitry of Trust and Trust Adaptation in Humans Neuron, 58 (4), 639-650 DOI: 10.1016/j.neuron.2008.04.009

Domes, G., Heinrichs, M., Michel, A., Berger, C., & Herpertz, S. (2007). Oxytocin Improves “Mind-Reading” in Humans Biological Psychiatry, 61 (6), 731-733 DOI: 10.1016/j.biopsych.2006.07.015

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

Jorge Moll, Roland Zahn, Ricardo de Oliveira-Souza, Frank Krueger, & Jordan Grafman (2005). The neural basis of human moral cognition Nature Reviews Neuroscience, 6

Zak, P., Kurzban, R., & Matzner, W. (2004). The Neurobiology of Trust Annals of the New York Academy of Sciences, 1032 (1), 224-227 DOI: 10.1196/annals.1314.025

Zak, P., Kurzban, R., & Matzner, W. (2005). Oxytocin is associated with human trustworthiness Hormones and Behavior, 48 (5), 522-527 DOI: 10.1016/j.yhbeh.2005.07.009


One response to “TED Talk: Oxytocin—the moral molecule

  1. Pingback: Lets Get Viral part deux: Viral Images | tonyajunemoore·

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