A meta-analysis was conducted on the accuracy of predictions of various objective outcomes in the areas of social and clinical psychology from short observations of expressive behavior (under 5 min). The overall effect size (r) for the accuracy of predictions for 38 different results was .39. Studies using longer periods of behavioral observation did not yield greater predictive accuracy; predictions based on observations under 1/2 min in length did not differ significantly from predictions based on 4- and 5-min observations. The type of behavioral channel (such as the face, speech, the body, tone of voice) on which the ratings were based was not related to the accuracy of predictions. Accuracy did not vary significantly between behaviors manipulated in a laboratory and more naturally occurring behavior. Last, effect sizes did not differ significantly for predictions in the areas of clinical psychology, social psychology, and the accuracy of detecting deception.

The way in which people move, talk, and gesture—their facial expressions, posture, and speech—all contribute to the formation of impressions about them. Many of the judgments we make about others in our everyday lives are based on cues from these expressive behaviors. Gordon Allport (1937) believed that expressive behaviors were important indicators of personality and that impressions from brief interactions were often verified upon further acquaintance. Allport and Vernon (1933) demonstrated that people's expressive styles were quite consistent across a variety of situations. They then began to investigate the accuracy of perceivers' impressions that were based on observations of these expressive styles. For reasons that have been discussed elsewhere, this issue—like other issues concerning the accuracy of interpersonal and...