Which experiment measured cognitive dissonance by varying the amount participants were paid to lie about a task's enjoyment?

The experiment that measured cognitive dissonance by varying the amount participants were paid to lie about a task's enjoyment is indeed the Festinger and Carlsmith Experiment. This study is foundational in social psychology and explores the concept of cognitive dissonance, which occurs when an individual holds two conflicting beliefs or attitudes.

In this experiment, participants were asked to perform a monotonous and tedious task and then were paid different amounts to convince others that the task was enjoyable. Those who received a smaller reward experienced greater cognitive dissonance because the minimal justification for lying (the low payment) conflicted with their true feelings about the task. To resolve this dissonance, they were more likely to change their attitudes about the task, convincing themselves that it was indeed enjoyable. On the other hand, those paid a larger amount felt justified in lying, thus experiencing less dissonance and maintaining their negative feelings about the task.

This experiment illustrated the principle that when individuals engage in behavior that contradicts their beliefs or knowledge, they will often change their beliefs to align with their actions to reduce the discomfort of dissonance.