The presence of a pair of eyes may unconsciously discourage people from lying, even when those lies would benefit victims of a natural disaster, according to the findings of a study published in Evolutionary Psychology.

Previous psychological studies have found that people behave less selfishly and are more likely to make personal sacrifices to benefit others when they can see a pair of eyes, even if those eyes are only in the form of a picture. Psychologists theorize that this happens because humans have a basic motivation, with evolutionary roots, to follow rules and social norms when they think they are being watched. The presence of eyes is thought to activate this instinct on a non-conscious level, even when it is obvious that the eyes do not belong to a real person.

In a new study of 199 Japanese university students, headed by Ryo Oda of the Nagoya Institute of Technology, the “watching eye effect” was put to the test in a case where two social values come into conflict: honesty and helping someone in need. Study participants were asked to roll a die to determine how much money the experimenters would donate to the Japanese Red Cross Society for relief for victims of the March 11, 2012 earthquake and tsunami. Participants rolled the die privately, giving them the opportunity to either lie or tell the truth about the amount to be donated to charity.

Half of the participants completed the study in a room containing a picture of a pair of eyes, while the other half were not exposed to the eyes. By comparing the values of the die rolls that people reported in comparison to what would occur by chance, researchers could tell approximately how many people had reported their rolls dishonestly. Many of those who were not “watched” by eyes had lied, telling the experimenters that they had rolled a higher value than they actually had, and sending more money to charity. In the group that was watched by eyes, people were more likely to tell the truth, sending less money to charity.

The authors of the study conclude from these findings that the watching eye effect on more generous giving found in previous studies works primarily encouraging people to follow the social norm of generosity. They suggest that the risks that come with being perceived by others as dishonest may be greater than those that come with being perceived as not being generous, and so when these two norms are in conflict the watching eye makes people more likely to prioritize telling the truth over giving to others.

They also conclude that these effects occur very rapidly and without conscious thought, which may one day make it possible to nudge people into being more honest and generous in some circumstances simply by exposing them to a pair of watching eyes.