Black Friday arrives with irresistible deals and urgent messages: “once a year” and “too good to miss.” Carts fill with items never intended to be bought, justified by the thought that the money would be spent eventually, so the savings must be worth it. Crowds of people drown out the question of whether any of it is truly needed.

Discomfort can arise when one holds two contradictory beliefs; this is the essence of cognitive dissonance. For example, the two thoughts of saving and spending are inconsistent, creating psychological tension. This theory was first presented by American social psychologist Leon Festinge in 1957 in his book, “A Theory of Cognitive Dissonance.” Building on his social comparison theory, which proposed that people have an innate drive to evaluate one’s attitude compared to others, he questioned how individuals navigate discrepancies between their own actions and beliefs.

When dissonance occurs, the mental discomfort must be reduced to maintain mental regulation and consistency. This can be done in two ways: by changing the thought or by changing the behavior. In the shopping example, changing the thought involves justifying the spending by framing the purchase as saving money, while changing the behavior involves choosing not to spend.

Cognitive dissonance can arise in virtually all aspects of life, but there are conditions that strengthen its effect. When an action is freely chosen, there's room for internal conflict, and if it’s also under high commitment, the choice can feel more meaningful. The dissonance is also greater if the action causes negative consequences, such as financial distress, especially when those outcomes were foreseeable at the time of the decision. These conditions shape how people reconcile their attitudes and behaviors.

Beyond shaping individual beliefs and actions, cognitive dissonance is a fundamental mechanism for evolution . New knowledge is only useful if it modifies what is already known, often conflicting with existing beliefs, which creates cognitive dissonance. When new information challenges what’s established, society reduces this tension through either rejection or rationalization. Over time, new knowledge proves its value and becomes integrated into what’s known, shaping human learning and reasoning.

Cognitive dissonance is considered one of the most influential and studied theories within social psychology. When in a state of dissonance, the process of reduction directly influences individual belief perceptions and actions, serving as an underlying propeller of cognitive evolution. While it typically influences behavior unconsciously, understanding and being actively aware of cognitive dissonance can be an opportunity for purposeful, positive change.