Rebecca Coffey

The Bejeezus Out of Me

The Biology of Lying

Is lying hard-wired into the human “tend and defend” response?

Posted Mar 31, 2014

When a mother in Ohio faked her address in order to send her child to a better public school, she got arrested. At trial she testified that she willingly lied to improve her child’s chances in life. She got jail time.

And not everyone was happy about that. The inclination to bend moral codes to help a child seems forgiveable, especially when doing so might make a real difference in the rest of that child’s life. Are we quick to forgive—and quick to lie—because “tend and defend” behavior is an evolved part of the mammalian repertoire?

Oxytocin is an evolutionarily ancient brain chemical underlying caring behaviors in both men and women. Nursing mothers, for example, have huge levels of it in their blood. It’s known widely as the “bonding hormone.” Psychologists at Israel’s Ben-Gurion University of the Negev report in the Proceedings of the National Academy of Sciences on an experiment that used oxytocin to test whether ramping up people’s oxytocin levels made them more likely to lie for each others’ benefit.

The experimenters worked with sixty healthy men who volunteered to administer to themselves nasally doses of either oxytocin or placebo. (They weren’t told which they were administering.) Then the experimenters assigned each man to a group of three. After the oxytocin had taken effect, a computer engaged each man individually in bets about the outcome of a heads-or-tails coin-toss game. The men were told that if they performed well, all three members of their group would be rewarded. The men reported their own scores, which, because they were alone in the room with the computer, gave them ample opportunity to lie. What they didn’t know, of course, was that the computer was also keeping score.

As expected, oxytocin increased the frequency with which men lied. The psychologists re-ran the experiment to see whether oxytocin would increase lying when the men were told that only they would benefit from the coin toss game. The men did not tend to lie for themselves. Which suggests that oxytocin was responsible only for the increased emotional bonding among men. Apparently, it is an affiliation hormone, and not, when artificially administered, a dishonesty drug.


Shaul Shalvia and Carsten K. W. De Dreub,"Oxytocin promotes group-serving dishonesty," Proceedings of the National Academy of Sciences.

Photo credit Katie Tegtmeyer

By day Rebecca Coffey is a science journalist, contributing to Scientific American, Discover, and Vermont Public Radio. She also presents a weekly radio spot, Family Friendly Science, on the nationally syndicated show, Daybreak USA. By night she is a novelist and humorist. Hysterical: Anna Freud's Story is due out in May 2014 from She Writes Press. Nietzsche's Angel Food Cake: And Other "Recipes" for the Intellectually Famished was published in October 2013 by Beck & Branch.

More Posts