We will recruit 64 children [n=32 at 12 months of age (plus or minus 2 months); n=32 at 18 months of age (plus or minus 2 months)] who are at-risk for ASD due to communication/language delays (at-risk group). The at-risk children will be matched at initial on chronological age, SES, and sex, to typically developing children (n=75) with no history of developmental delays. These 139 participants will hereafter be referred to as the toddler sample. At the 36 month final visit, diagnostic status (e.g. ASD, non-ASD specific delays, catch up) will be determined for children in the at-risk group. In addition, 10 healthy adults, aged 18-40 will serve as control participants for the purpose of piloting the functional paradigms for the MRI portion of the protocol.