Festinger and Carlsmith conducted a famous experiment in the field of social psychology. This experiment was related to:

The correct option is Cognitive dissonance.

Leon Festinger and James Carlsmith conducted a classic experiment in 1959 to test the theory of cognitive dissonance. Cognitive dissonance refers to the mental discomfort a person experiences when holding two conflicting beliefs, or when their behavior contradicts their beliefs.

In their study, participants were asked to perform extremely boring and repetitive tasks (such as turning wooden pegs on a board for an hour). Afterward, they were asked to tell the next participant (who was actually a confederate of the experimenter) that the tasks were highly exciting and enjoyable. For doing this, participants were paid either $1 or $20.

The researchers found that participants who were paid only $1 rated the boring task as significantly more enjoyable than those who were paid $20. According to cognitive dissonance theory, the participants paid $20 experienced little dissonance because they had a strong external justification (a large sum of money for the time) for lying. However, those paid $1 experienced high dissonance because $1 was insufficient external justification for lying. To resolve this psychological discomfort, they adjusted their internal attitude to align with their behavior, genuinely convincing themselves that the task was fun.