Altruism, Reward and The Neuropeptide of Brotherly Love

Phoebe: This isn’t good deed. You just wanted to go on TV. That’s totally selfish.

Joey: Whoa! What about you, having those babies for your brother? Talk about selfish!

Phoebe: What? What are you talking about?

Joey: Well, yeah, it was a really nice thing and all, but it made you feel really good, right?

Phoebe: Yeah. So?

Joey: It made you feel good, so that makes it selfish. Sorry to burst that bubble, Pheebs, but selfless good deeds don’t exist. Okay?”

Phoebe: I’m gonna find a selfless good deed. I’m gonna beat you, you evil genius.

(S5E4 Friends, The One Where Phoebe Hates the PBS)

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Source: Netflix. S5E4 Friends, The One Where Phoebe Hates the PBS


Let’s consider the concept of altruism. What constitutes an altruistic behavior? The definition relevant to psychologists and biologists is less stringent than what Joey had in mind. Imagine you are in a rush and happened to see an old lady on crutches struggling to cross the street.

Helping the old lady cross the street? That is altruistic. Helping the old lady cross the street when she is your mother’s second cousin? Still altruistic. Helping the old lady cross the street when your colleague is watching? Still altruistic. The point is, costly behaviors performed to benefit other individuals broadly fall under the umbrella of “altruistic behavior” in behavioral research. A purely selfless motivation behind those behaviors is not demanded. If anything, researchers are exactly trying to find out why humans frequently engage in these seemingly selfless behaviors. A recent finding says that “it makes you feel good” is indeed one of the reasons (Moll et al., 2006).

The experiment was done like this. People had their eyes fixated on the center of a computer screen. Then, a statement popped out: “Allowing euthanasia for the terminally ill”. As the statement faded, a random payoff plan popped out: YOU: $0, ORG: $+5, YES or NO?


An illustration of the donation task in Moll et al.,’s experiment. Source: depositphotos

People had to make a choice. To choose YES is to accept the payoff plan, where people would, according to the plan, receive or lose money to themselves, and donate or not donate money to the organization behind the cause (Note: donation money came from a fund from a third party, not the participants). Before starting, people were told that they could earn up to $128 in this neuroimaging study, but their decisions in the task would directly affect the ultimate amount of money they receive.

In this study, rejecting a payoff plan that offers you money but makes donations to a cause that you find unjust is an altruistic behavior (YOU: $+2, ORG: $+5, NO); similarly, endorsing a payoff plan that costs you money but makes donations to a cause that you approve of is also altruistic (YOU: $-2, ORG: $+5, YES). When people were making those decisions, they were hooked up to an fMRI scanner. It was found that the ventral tegmental area (VTA) and the ventral striatum were activated both when people performed these altruistic behaviors and when people received a pure monetary gain.

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The mesolimbic reward pathway. Source: (Telzer, 2016). Developmental Cognitive Neuroscience.

The VTA and the ventral striatum are both part of the mesolimbic reward pathway. Simply put, if you were a laboratory rat, you would pull a lever like crazy for a direct electrical stimulation to these areas (Wise, 2002), because it feels good. So, it would seem that supporting a cause that you believe in at the expense of personal loss is almost as good as getting money into your own pocket. This experiment, therefore, provides some preliminary evidence that altruism can be rewarding. This study also found something else that was interesting— a region called subgenual area was only activated when people made altruistic decisions. The subgenual area is frequently associated with functions mediating social attachment. And more specifically, it is critical to the release of a neuropeptide called oxytocin.

Oxytocin, or what I call “The Neuropeptide of Brotherly Love”, has been shown to increase trust and promote altruism in humans. A single dose of oxytocin made people more likely to transfer larger amounts of money to strangers in an investment game (Kosfeld, Heinrichs, Zak, Fischbacher, & Fehr, 2005).

Make oxytocin, not war.  Source: Etsy

Oxytocin could even bias people towards social altruism. It was found that high concentration of circulating oxytocin corresponded to increased willingness to donate money only if the charitable cause was framed to be socially relevant (Marsh et al., 2015). For example, between “donating to preserve a rainforest area in the Congo Delta” (pro-environmental) and “donating to preserve the indigenous people living there” (pro-social), oxytocin prompted people to donate with more alacrity when their fellow humans, not trees or plots of land, were the beneficiaries. There is a tender, loving glow around oxytocin, but it could also fuel wars and battles by forging the bond between brothers in arms, so that they are united and motivated to defeat an outgroup (De Dreu et al., 2010). If you think about it, the brave soldiers at battle, self-sacrificing so that their group would prevail, are all altruists.


Taken together, from the first study we saw that altruistic behaviors activated the same reward pathway as earning money, but there was one area, the subgenual area, that was activated uniquely in altruistic behaviors. The subgenual area and altruism is probably linked by the subgenual area’s control over the release of oxytocin, which had been repeatedly shown to induce altruistic behaviors. And, in turn, the generation of altruistic behavior is possibly coupled to the reward circuit to motivate people to reproduce this pro-social behavior.

This is one over-simplified, possible account of altruism in humans. There are so many more aspects to this topic than I have the time to address. I’ll leave the rest for you to find out! There is one direction for you to dig: search term: altruism and fitness. If you find anything interesting, be altruistic, take some time and effort to blog about it for the intellectual well-being of others.



De Dreu, C. K. W., Greer, L. L., Handgraaf, M. J. J., Shalvi, S., Van Kleef, G. A., Baas, M.,  Feith, S. W. W. (2010). The Neuropeptide Oxytocin Regulates Parochial Altruism in Intergroup Conflict Among Humans. Science, 328(5984), 1408 LP-1411.

Kosfeld, M., Heinrichs, M., Zak, P. J., Fischbacher, U., & Fehr, E. (2005). Oxytocin increases trust in humans. Nature, 435, 673. Retrieved from

Marsh, N., Scheele, D., Gerhardt, H., Strang, S., Enax, L., Weber, B., … Hurlemann, R. (2015). The Neuropeptide Oxytocin Induces a Social Altruism Bias. The Journal of Neuroscience, 35(47), 15696 LP-15701.

Moll, J., Krueger, F., Zahn, R., Pardini, M., de Oliveira-Souza, R., & Grafman, J. (2006). Human fronto–mesolimbic networks guide decisions about charitable donation. Proceedings of the National Academy of Sciences, 103(42), 15623 LP-15628.

Wise, R. A. (2002). Brain Reward Circuitry: Insights from Unsensed Incentives. Neuron, 36(2), 229–240.

Source of Featured Image: National Public Radio

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