Pivotal response treatment (PRT) is a well-known, motivational treatment for children with autism spectrum disorder (ASD). Much research has shown that the treatment is effective in targeting motivation, which ultimately leads to more widespread positive effects on communication, behavior, and social skills. While behavioral and social-communication measures have traditionally been used as outcome data, this project will improve understanding of how PRT actually changes the brains of children with autism to bring about these behavioral and social improvements. This is relevant to Autism Speaks’ goal of identifying biomarkers and improving treatment for children with ASD. This project will examine the treatment’s effects on brain regions previously found to be involved in social perception, or the initial stages of evaluating the social intentions of others. Four to six-year-old children with ASD will receive 4 months of PRT and will undergo a functional magnetic resonance imaging (fMRI) scan before and after treatment. They will watch videos of moving dots. Some of these dots will look like humans moving and some will look random. The “human” videos were made by putting lights on all the major joints of a human and then videotaping him in the dark so all you can see are the white lights. When typically developing children watch the “human” videos, social parts of the brain are activated. These social parts of the brain are predicted to show more activation after treatment. This will determine if treatment changes the way children with ASD look at “human” versus “random” motion. In addition, these results will help to improve understanding of the effect PRT has on the brain. In order to examine the relationship between the brain and behavior, participants will be given a variety of tests and assessments before and after treatment. These studies are predicted to replicate previous reports of positive behavioral changes in these children. Additionally, it is hypothesized that greater positive behavioral changes will correlate with increased activation in key social parts of the brain. The collection of both behavioral and fMRI outcome data will also allow the investigation of the connection between brain and behavior in children with ASD and translate these findings to predict response to treatment based upon neural response at intake, allowing better tailoring of treatment protocols to each child based upon their initial behavioral and neural response profile.