Self-monitoring, a concept introduced in the 1970s by Mark Snyder, describes the extent to which people monitor their self-presentations, expressive behavior, and nonverbal affective displays. Snyder held that human beings generally differ in substantial ways in their abilities and desires to engage in expressive controls (see dramaturgy). Self-monitoring is defined as a personality trait that refers to an ability to regulate behavior to accommodate social situations. People concerned with their expressive self-presentation (see impression management) tend to closely monitor their audience in order to ensure appropriate or desired public appearances. Self-monitors try to understand how individuals and groups will perceive their actions. Some personality types commonly act spontaneously (low self-monitors) and others are more apt to purposely control and consciously adjust their behavior (high self-monitors). Recent studies suggest that a distinction should be made between acquisitive and protective self-monitoring due to their different interactions with metatraits. This differentiates the motive behind self-monitoring behaviours: for the purpose of acquiring appraisal from others (acquisitive) or protecting oneself from social disapproval (protective).
