Happy faces considered trustworthy irrespective of perceiver's mood: Challenges to the mood congruency effect

Interpersonal trust is affected by the emotional states and facial expressions of the interacting parties. This study investigated the interactive (combined) effects of emotions and facial expressions by simultaneously manipulating both variables. Three laboratory experiments were conducted using a face evaluation task (i.e., choosing the most trustworthy face from a face pair) with happy, sad, and neutral faces. Experiment 1 tested the effect of facial expressions on trust judgments. Experiments 2 and 3 manipulated both facial expressions and perceiver's emotions. The results of the three experiments showed that happy faces were more often chosen as the most trustworthy relative to neutral and sad faces, and that perceiver's emotions did not influence trust judgment. These results indicated that other's facial expressions as dominant social cue would bias interpersonal trust, which might cause security issue in online social networks.