In three articles, I examine the evolved function of social anxiety. Social anxiety—like other responsive defenses—is useful only when the magnitude of the response is appropriate to the demands of situations that involve genuine social threats. In the first article, I review the literature on the ultimate function of social anxiety and argue that the computational systems that underlie social anxiety function to: (1) detect high stakes social interactions; and, (2) minimize the risk of subsequent negative evaluation. In the second article, I present the results of a series of studies in which participants from across the distribution of levels of trait social anxiety completed a threatening or non-threatening priming task, then were asked to identify the emotion displayed in a series of faces. Results revealed a curvilinear relationship between dispositional social anxiety scores and response time, suggesting that moderate social anxiety is advantageous in certain situations. The final article used content analysis to examine the characteristics of the interaction partners and types of situations that college-aged participants recall—as well as the vocabulary and pronouns used—when asked write about an anxiety-provoking situation.