Stereotyped movements are one of the defining characteristics of autism spectrum disorders (ASDs), commonly taking the form of body-rocking, hand-flapping, and other repetitive movements. Recent work has shown that environmental events may cause individuals with ASD to engage in more or less stereotypy (stereotyped movements); therefore, environmental alterations have the potential to decrease the motivation for engaging in stereotypy. The present study will test the efficacy of several possible methods of decreasing the motivations for stereotypic behaviors. Researchers will determine whether access to highly valued toys or objects can decrease stereotypy, and if these decreases continue after toys are removed. They will also evaluate whether stereotypy is lower after individuals are permitted to engage in stereotypic behaviors for an extended period of time. Finally, they will test the hypothesis that systematically pairing a specific stimulus with periods of low motivation to engage in stereotypy can result in the stimulus acquiring motivating properties, so that after a training period, presentation of the stimulus would decrease the motivation towards stereotypy. This research may provide new methods of decreasing stereotypic behaviors in children with ASD, which could be used by teachers or parents during critical training periods in order to minimize interference from these behaviors.