Self-monitoring is a concept introduced during the 1970s by Mark Snyder, that shows how much people monitor their self-presentations, expressive behavior, and nonverbal affective displays. Human beings generally differ in substantial ways in their abilities and desires to engage in expressive controls (see dramaturgy). It 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).
During the 1970s when the self-monitoring concept was introduced it became part of two larger ongoing debates. Within personality research there was the tension between traits and situations. Were people more inclined to behave consistent with their personality traits or were they influenced by the immediate social situation? The self-monitoring construct offered a resolution to this debate because there was no need to argue that humans were influenced entirely by either traits or situations. High self-monitors were better predicted by their social environment (situation) while low self-monitors were better predicted by their traits. Another debate that was raging during this time period within social psychology was whether or not attitudes were good predictors of behavior. The self-monitoring construct offered a resolution to this debate as well because it posited that low self-monitors would behave largely consistent with their attitudes, while attitudes would be poor predictors of behavior for high self-monitors. The self-monitoring construct fit neatly into the arguments of the day where high self-monitors affirmed the situation-oriented view typically associated with social psychology, while the low self-monitors affirmed the trait-oriented view typically associated with personality psychology.