Dr. Mayhew was interested in adolescents' reaction to disappointment. At the beginning of a local rock concert, Dr. Mayhew had the announcer broadcast that the band would perform an encore performance. All of the adolescents continued to stand and wait for the encore performance following the formal conclusion of the concert. Approximately 60 minutes later the announcer broadcast that the band already left and was unable to perform. Trained observers were placed throughout the concert arena and recorded the reactions of the adolescents in the audience following the news of the cancelled encore performance. The best description for this would be a(n):