Oxytocin, the love hormone is the reason why some people bend ethical rules and even lie to help those closer to them - like their colleagues or family members.
Oxytocin is the hormone that the body naturally produces to stimulate bonding.
According to a study, oxytocin caused participants to lie more to benefit their groups, and to do so more quickly and without expectation of reciprocal dishonesty from their group.
"People are willing to bend ethical rules to help the people close to us. This raises an interesting, although perhaps more philosophical, question: Are all lies immoral?" asked Shaul Shalvi of Israel-based Ben-Gurion University of the Negev (BGU)'s department of psychology.
"These findings reveal that dishonesty is somewhat rooted in the brain. Oxytocin shifts the decision-maker's focus from self to group interests," Shalvi added.
The research focused on ethical decision-making and the justifications people use to do wrong and still feel moral.
It looked at what determines how much people lie and which settings increase people's honesty as very little is known about the biological foundations of immoral behaviour.
The results highlight the role of bonding and cooperation in shaping dishonesty, providing insight into when and why collaboration turns into corruption.
Higher levels of oxytocin correlate with greater empathy, lower social anxiety and more pro-social choice in anonymous games, reduction in fear response, and greater trust in interpersonal exchange.
In the experiment by Shalvi and Carsten KW De Dreu of University of Amsterdam, 60 male participants received a dose of either oxytocin or placebo.
They were then split into teams of three and asked to predict the results of 10 coin tosses.
Participants were asked to toss the coin, see the outcome and report whether their prediction was correct.
They knew that for each correct prediction, they could lie and earn more money to split between their group members, who were engaging in the same task.
The statistical probability of someone correctly guessing the results of nine or 10 coin tosses is about one percent.
Yet, 53 percent of those who were given oxytocin claimed to have correctly predicted that many coin tosses, which is extremely unlikely.
Only 23 percent of the participants who received the placebo reported the same results, said the research published in the journal Proceedings of the National Academy of Science (PNAS).