It has repeatedly been observed that autism spectrum disorders (ASD) disproportionately affect males relative to females. Although many hypotheses attempt to explain this bias, no clear answers have emerged due to inconsistent and incomplete characterization and small sample sizes. This study seeks to examine sex- specific differences in individuals with ASD using methods including deep phenotyping and genotyping. Researchers will quantitatively phenotype multiple behavioral domains and measure several key ASD-related neural systems at the level of brain structure, connectivity, and function. Additionally, investigators will measure copy number variation (CNV) and single nucleotide variation (SNV) for these participants and their parents, which will allow for the testing of sex- and circuit-specific genotype-phenotype hypotheses. Through this study, investigators will Identify sex-differences in brain mechanisms underlying ASD, search for relationships between brain mechanisms and underlying genetic differences, and determine the mechanisms underlying heterogeneity in the presentation and severity of ASD in boys and girls.