A Fake Smile Thwarts Cheater Detection

People can discriminate cheaters from cooperators on the basis of negative facial expressions. However, such cheater detection is far from perfect in real-world situations. Therefore, it is possible that cheaters have the ability to disguise negative emotional expressions that signal their uncooperative attitude. To test this possibility, emotional intensity and trustworthiness were evaluated for facial photographs of cheaters and cooperators defined by scores in an economic game. The facial photographs had either posed happy or angry expressions. The angry expressions of cheaters were rated angrier and less trustworthy than those of cooperators. On the other hand, happy expressions of cheaters were higher in emotional intensity but comparable to those of cooperators in trustworthiness. These results suggest that cheater detection based on the processing of negative facial expressions can be thwarted by a posed or fake smile, which cheaters put on with higher intensity than cooperators.