Greater Good

A new study has tackled one of the most crucial questions for an election year: Who can you trust?

In the study, published in the journal Emotion, researchers looked at how subtle facial cues help individuals decide whether another person is trustworthy. They devised a simple computer game in which participants started with 10 dollars and could choose either to pass it on to a partner or keep it for themselves. If they passed it on, the amount was tripled to 30 dollars, which the partner could then take entirely for herself. If the partner chose not to take the money for herself, each player would receive 15 dollars.

Before starting the game, the researchers showed study participants short video clips of several different people, asking the participants to choose one as their partner for the game. The people in the videos displayed either a genuine smile, a fake smile, or a neutral facial expression. Given the rules of the game, the participants obviously had incentive to choose the player who seemed most trustworthy.
Though the facial expressions were subtle and fleeting, they strongly influenced how the participants made their decisions. Players with the genuine smile were chosen the most frequently, while those with the neutral face were chosen the least. The genuine smilers were also rated as the most likeable, attractive, and cooperative; the neutral faces scored the lowest on all these scales.

In their Emotion paper, the researchers say their results suggest humans “seem to have evolved special systems that allow them to detect cheaters who fake emotions to appear trustworthy and cooperative.” Yet if fake smiles are usually associated with cheaters, why did the fake smilers seem to be more desirable partners than the neutral faces?

Arvid Kappas, one of the study’s authors, says the neutral faces may have seemed suspicious because they didn’t follow a social norm: smiling when presenting oneself. “I think most people are aware that not every person who greets you with a smile is truly happy about seeing you, but they follow the etiquette, the social contract,” says Kappas, a psychology professor at Jacobs University in Germany. “People who do not follow this social contract appear negative.”