In an experiment performed by Steven Sherman in 1980, two sets of people were asked over the phone to donate three hours of time to a cancer drive. One group was simply asked if they would do it. They said yes. Four percent showed up. The other group was asked if they thought they would show up if they were to be asked. Most said they would show up. Almost all of them did. The second group had made an assumption about their own personality, and once they had painted a portrait of what kind of person they were, they had to conform to the idea or risk cognitive dissonance.
