One of the core features of autism spectrum disorder (ASD) is restricted and repetitive patterns of behaviours and interests. A related characteristic that has often been reported in descriptions of people with ASD is a strong preference for familiar stimuli. However, many of the basic processes involved in preference development have not yet been thoroughly studied in individuals with ASD. This project will examine a basic method of preference development in youths with ASD. In typically developing people, increased familiarity with stimuli (e.g., people, places, objects, etc.) generally results in greater comfort with, and liking of, them. This phenomenon is called the "mere repeated exposure effect" (MRE effect). The main goal of the proposed research is to examine whether the MRE effect is intact in individuals with ASD. It is expected that, while participants with ASD will require more exposure to stimuli before they begin demonstrating increases in liking ratings, their preferences for stimuli will persist longer (i.e., across more exposures) than those of comparison participants. The results of this study may prove noteworthy for several reasons. In particular, differences in how people with ASD develop preferences will be crucial to consider in designing educational programs and behavioural interventions for these individuals. We also expect that the results of this study will help us to better understand some of the core symptoms of ASD (particularly restricted interests and preference for sameness) and will have important implications for the early identification of this disorder.