Cognitive dissonance, a psychological theory proposed by Leon Festinger in 1957, describes the mental discomfort experienced when an individual holds contradictory beliefs, values, or attitudes simultaneously. An illustrative experiment on this phenomenon was conducted by Festinger and Carlsmith in 1959. Participants were asked to perform a monotonous task and were subsequently paid either $1 or $20 to persuade another participant (a confederate) that the task was interesting and enjoyable. Afterward, those who were paid $1 experienced greater cognitive dissonance compared to those who were paid $20. To resolve this dissonance, the $1 group altered their attitudes, convincing themselves that the task was genuinely enjoyable. Conversely, the $20 group had sufficient external justification for lying, thus experiencing less dissonance and no significant change in attitude. This experiment demonstrated how individuals rationalize their behavior to reduce cognitive dissonance and achieve internal consistency.