The illusion of control is the tendency for people to overestimate their ability to control events, for instance to feel that they control outcomes that they demonstrably have no influence over. The effect was named by psychologist Ellen Langer and has been replicated in many different contexts. It is thought to influence gambling behavior and belief in the paranormal. Along with illusory superiority and optimism bias, the illusion of control is one of the positive illusions. Although, the idea of illusion of control has been studied prior to Langer. Psychological theorists have consistently emphasized the importance of perceptions of control over life events. One of the earliest instances of this is when Adler argued that people strive for proficiency in their lives. Heider later proposed that humans have a strong motive to control their environment and White hypothesized a basic competence motive that people satisfy by exerting control. Weiner, an attribution theorist, modified his original theory of achievement motivation to include a controllability dimension. Kelley then argued that people’s failure to detect noncontingencies may result in their attributing uncontrollable outcomes to personal causes. Later on, Lefcourt argued that the sense of control, the illusion that one can exercise personal choice, has a definite and a positive role in sustaining life. Nearer to the present, Taylor and Brown argued that positive illusions, including the illusion of control, foster mental health.

The illusion is more common in familiar situations, and in situations where the person knows the desired outcome. Feedback that emphasizes success rather than failure can increase the effect, while feedback that emphasizes failure can decrease or reverse the effect. The illusion is weaker for depressed individuals and is stronger when individuals have an emotional need to control the outcome. The illusion is strengthened by stressful and competitive situations, including financial trading. Though people are likely to overestimate their control when the situations are heavily chance-determined, they also tend to underestimate their control when they actually have it, which runs contrary to some theories of the illusion and its adaptiveness. People also showed a higher illusion of control when they were allowed to become familiar with a task through practice trials, make their choice before the event happens like with throwing dice, and when they can make their choice rather than have it made for them with the same odds. People even are more likely to show control when they have more answers right at the beginning than at the end even when the people had the same number of correct answers.

The illusion might arise because people lack direct introspective insight into whether they are in control of events. This has been called the introspection illusion. Instead they may judge their degree of control by a process that is often unreliable. As a result, they see themselves as responsible for events when there is little or no causal link. In one study, college students were in a virtual reality setting to treat a fear of heights using an elevator. Those who were told that they had control, yet had none felt as though they had as much control as those who actually did have control over the elevator. Those who were led to believe they did not have control said they felt as though they had little control.