Psychological Science, Ahead of Print.
According to expectancy theory, outcome expectancies are first formed vicariously (through observing other people) and then through direct experience. This cohort-sequential longitudinal study explored these expectancy origins in 1,023 youths (52% female, ages 10.5–15.5 years at recruitment, M = 12.47 years, SD = 0.95). Discontinuous multilevel growth models described patterns of change in expectancies before and after the first experience of distinct drinking milestones (i.e., first sip, first full drink, first heavy-drinking situation). Youths’ expectations for positive and negative drinking outcomes generally increased and decreased over adolescence, respectively, reflecting general developmental trends. Drinking experiences altered learning trajectories, however, reifying positive expectancies and invalidating negative expectancies at each milestone and altering the course of expectancy change thereafter. For positive outcome expectancies, the influence of direct experience on learning was stronger when drinking milestones were met at an earlier age. Conversely, invalidation of negative expectancies was stronger when the first-drink milestone was met at a later age.