Development of Prosocial Behaviors and Related Brain Network in Infants of High and Low Risk of ASD

Inclusion Criteria: * Subjects were enrolled as high-risk if they had an older sibling with a clinical diagnosis of ASD confirmed on the Autism Diagnostic Observation Schedule, second edition (ADOS-2) or Autism Diagnostic Interview (ADI-R). * Subjects were enrolled in the low-risk group if they had an older sibling without evidence of ASD and no family history of a first or second-degree relative with ASD. Exclusion Criteria: 1. diagnosis or physical signs strongly suggestive of a genetic condition or syndrome (e.g., fragile X syndrome) reported to be associated with ASDs; 2. a significant medical or neurological condition affecting growth, development or cognition (e.g., CNS infection, seizure disorder, congenital heart disease); 3. sensory impairment such as vision or hearing loss; 4. low birth weight (\<2000 grams) or prematurity (\<37 weeks gestation); 5. possible perinatal brain injury from exposure to in-utero exogenous compounds reported to likely affect the brain adversely in at least some individuals (e.g., alcohol, selected prescription medications); 6. contraindication for MRI (e.g., metal implants); 7. a family history of intellectual disability, psychosis, schizophrenia or bipolar disorder in a first-degree relative.