Background: Trusting other people is necessary for satisfactory and successful social interaction. A person’s perceived trustworthiness is related to perceived facial happiness. We investigated how trustworthy someone with a smiling face looks depending on changes in eye expression.
Method: Video-clips of dynamic expressions were presented, with different combinations of the mouth (smiling vs. neutral) and the eyes (happy, neutral, surprised, sad, fearful, disgusted, or angry). Participants judged how happy (happiness task) or trustworthy (trustworthiness task) the expressers were.
Results: Both happiness and trustworthiness judgments and reaction times varied as a function of small changes from happy to non-happy eyes in a smiling face, and depending on the specific nature of the eye expression, with angry eyes being particularly detrimental.
Conclusions: Perception of facial happiness is more dependent on the smiling mouth, whereas trustworthiness relies more on eye expression. Judgments of untrustworthiness are especially sensitive to incongruence between the eyes and the mouth.