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Why Betrayal Hurts So Much (and Who Seeks Revenge)

New research on what happens in the jilted brain.

Andrey Arkusha/Shutterstock
Source: Andrey Arkusha/Shutterstock

Everyone faces betrayal at some point in life. Perhaps it’s a romantic partner who cheats, or a friend who takes advantage of you. No matter how much the person apologizes, you can’t manage to tap into your inner reservoir of forgiveness. To ease your pain, you seek retribution, if not revenge.

The violation of our trust is at the root of betrayal. It makes sense, then, to try to identify where that feeling of trust comes from. According to Shuxia Yao and colleagues (2014), of the University of Electronic Science and Technology of China, trust involves oxytocin, a hormone manufactured by the brain’s hypothalamus that is involved in mother-infant bonding. However, oxytocin also acts more generally in social bonding, and some believe it is a key component in the psychological experience of trust.

While we tend to think of trust as essential mainly to romantic relationships, Yao and her research team maintain, on the basis of previous research, that oxytocin is also involved in business or economic transactions. When you make a deal with someone, you want to know that the person you’re shaking hands with will come through on his or her end of the bargain. If not, there would be no point in making an agreement. In business, as in romance, you need to be sure that your partner will treat you fairly. We tend to presume that people will look out for their own best interests, but also that they, in turn, will respect ours.

With this in mind, Yao et al. sought to determine if they could experimentally manipulate restoration of trust in people led to believe that they’d been the victims of a betrayal. Participants played an investment game in which they were told that if they gave money to their partners, all would stand to benefit. The partners weren’t visible to participants. (In fact, they didn’t actually exist.) The money was also a currency invented by the experimenters but to the participants, it still felt real.

The betrayal came about when, only after giving away their money, did participants (the “trustors”) learn that their partners (the “trustees”) would give them nothing back in return—instead of the tripled investment they believed they would receive. However, not all of the virtual partners betrayed the trustor; the experimental manipulation involved some partners committing the betrayal and some partners acting as promised.

This was Part 1 of the study. Following the investment game, Yao and her team administered, via a nose spray, either a dose of oxytocin (to one group of participants) or a dose of a placebo (to the other group). The experiment then resumed 45 minutes later with Part 2, in which researchers told participants that the trustees had been asked to think over their behavior in Part 1 and change their actions if they so desired. (Again, this was all experimentally manipulated, as there were no actual trustees.) In the trust restoration condition, the trustee gave the money back to the participant. In the apology condition, the trustee took responsibility for the unfair behavior and expressed remorse. In the fair and “nothing” conditions, the trustee made no reply.

Now Round 2 of the investment game got underway. Participants once again could decide how much to invest in their partner. If trust had been re-established, one would imagine participants should go ahead and invest away—but if they were still fuming over unfair treatment, they’d likely hold onto their experimental money. In fact, the trustors did tend to hand over their cash if the trustee apologized or gave back the initial investment, especially in the repayment condition. As Yao and team point out, if you want to right a financial wrong, the best way to do so is to give back the money you unfairly took. Apologies are nice, but they don’t pay the bills.

And what about the role of the brain’s trust chemical? If oxytocin is involved in trust, then the trustors who took a whiff of the substance should show a stronger trust-restoration effect than those who sniffed a placebo. Here’s where the study took a surprising turn: Among women (and not men), those in the oxytocin condition became less trusting—not more—after a betrayal. In fact, they were particularly less trusting in the trust-restoration condition. In short, they were seeking revenge. Oxytocin did not have the same effect with the males in the study, and among women, the effect of betrayal was even stronger for those measured as high in the general tendency to forgive others. As the authors conclude, “ some contexts oxytocin may make normally forgiving women significantly less tolerant of broken trust” (p. 1791).

These surprising findings suggest that oxytocin, though generally a trust-enhancing chemical, can influence women exposed to it, particularly those ordinarily disposed to forgiveness, more likely to seek revenge after betrayal. The reason that the effect was stronger for females than males could be, as the authors suggest, due to generally higher oxytocin levels in general in women. It’s possible that to reach similar levels of oxytocin to stimulate the trust betrayal reaction, men need higher doses.

This fascinating study suggests that if you’re the victim of a betrayal, your brain and personality may interact to make you want to seek revenge. It’s better not to betray someone at all. However, as the study suggests, if you’re the betrayer, the road to restored harmony may present some unexpected hazards.

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Copyright Susan Krauss Whitbourne 2015


Yao, S., Zhao, W., Cheng, R., Geng, Y., Luo, L., & Ken, K. M. (2014). Oxytocin makes females, but not males, less forgiving following betrayal of trust. International Journal Of Neuropsychopharmacology, 17(11), 1785-1792. doi:10.1017/S146114571400090X

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