Psychology has long recognized that people must know themselves in order to survive and adapt in life. The value of self-knowledge stems from the fact that the self represents the only constant throughout life. Because of this if the self is well defined, it can provide a solid basis of values, preferences, and attitudes to manage the many decisions of daily life. Clear self-knowledge helps people to quickly decide and express their views on issues such as capital punishment, the ideal profession, or their tastes in music, whereas the absence of clear self-knowledge can leave an individual paralyzed by these decisions. Given the importance of self-knowledge, psychologists have spent a great deal of time attempting to understand how people come to know themselves.
Self-perception theory represents one of the most influential theories of how self-knowledge unfolds. Developed by social psychologist Daryl Bem self-perception theory consists of two basic claims. First the theory claims that people come to know their own attitudes, beliefs, and other internal states by inferring them from their own behavior and the circumstances under which they occur. So a student who observes that he or she constantly reads psychology books may infer an interest in psychology. Second the theory claims that when internal cues are weak, the individual is in the same position as an outside observer who must rely upon the external cues of their behavior to infer their own inner characteristics. In this case people’s conclusion that they genuinely like psychology will be reinforced if there are no external incentives to explain their behavior (e.g., grades), and they have no clear prior opinions regarding psychology. Thus people simply use their behavior and the circumstances in which it occurs to infer their own beliefs and attitudes.
One reason why self-perception theory has been so influential stems from its simplicity as an explanation for how self-knowledge develops. That is people come to know themselves merely by observing their own behavior. Beyond its simplicity, however, self-perception theory has been so influential because it provides an important contrast to the most famous psychological theory of how behavior shapes self-knowledge: cognitive dissonance theory. Cognitive dissonance theory assumes that people are motivated to maintain consistency between self beliefs and experience an unpleasant state of dissonance when they hold two inconsistent beliefs about the self. Thus the inconsistency between the thoughts "I do not like psychology" and "I constantly read about psychology" arouses dissonance, and people are motivated to reduce dissonance by changing one of those thoughts. The most direct way to resolve dissonance is to change the prior belief ("I do not like psychology") to align with the behavior ("I spend a great deal of time learning about psychology"). That is the person can resolve dissonance by making their initial attitude more favorable (I really do like psychology) and, hence, consistent with their behavior.
There are two differences between cognitive dissonance theory and self-perception theory. First unlike cognitive dissonance theory, self-perception theory does not assume that any motivational state (e.g., dissonance reduction) is necessary for change in self-knowledge. In fact self-perception theory only requires people’s willingness to infer their own attitudes and beliefs by considering the environmental and dispositional causes for their own actions for changes in self-knowledge to occur. Second self-perception theory claims that people can use their own behavior to infer self-knowledge when the internal cues of prior beliefs are ambiguous or weak, whereas cognitive dissonance theory assumes that people adjust self-knowledge only when the internal cues of prior beliefs are clear and conflict with their freely chosen behavior. Taken together these two differences have led psychologists to suggest that both self-perception theory and cognitive dissonance theory can explain the adjustment of self-knowledge under different conditions. Self-perception theory explains the creation of new self-knowledge following behavior that does not conflict with clear initial self-views whereas cognitive dissonance explains change in existing self-knowledge following freely chosen behavior that does conflict with clear initial self-views.
The resolution of the self-perception theory versus cognitive dissonance theory debate represents one of the greatest contributions of self-perception theory. Indeed psychology only becomes better when old theories are challenged and complemented by new theories. However the contribution of self-perception theory extends beyond cognitive dissonance theory through its ability to account for a wider variety of self-attribution phenomenon. Most notably self-perception theory can explain how people develop self-knowledge from behavior even when there is no inconsistency between prior beliefs and behavior. So self-perception theory can explain how people infer that they intrinsically enjoy engaging in an activity (psychology) that they once found intrinsically unenjoyable (behavior-belief inconsistency) when there are not obvious situational incentives to explain their behavior (e.g., money for grades). In addition, however, self-perception theory can explain how people infer that they do not intrinsically enjoy engaging in an activity (psychology) that they once found intrinsically enjoyable (behavior-belief consistency) when there are obvious situational incentives that can explain their behavior (e.g., money for grades). Cognitive dissonance theory cannot explain this type of change in self-views because the behavior of task engagement (reading psychology) is not inconsistent with the initial belief that they enjoy the task. Self-perception theory can explain this type of change in self-beliefs because it does not assume that an inconsistency must exist between initial beliefs and behavior for people to adjust self-knowledge. That is people infer that they must be engaging in the task to earn the external rewards rather than to satisfy their intrinsic interest in the activity. Self- perception theory not only explains the change in self-views produced by external rewards that cannot be explained with cognitive dissonance but also emphasizes the dangers of offering people incentives to engage in tasks that they are already interested in. The ability to explain changes in self-knowledge under a wide range of conditions makes self-perception theory one of the most influential theories of how people get to know themselves.