Final answer:
Impaired social skills, repetitive motor behaviors, and preoccupation with specific subjects are behaviors diagnostic of autistic disorder.
Step-by-step explanation:
A characteristic symptom of Autism Spectrum Disorder (ASD) is impaired social skills. Children with autism may have difficulty making and maintaining eye contact and reading social cues. They also may have problems feeling empathy for others. Other symptoms of ASD include repetitive motor behaviors (such as rocking back and forth), preoccupation with specific subjects, strict adherence to certain rituals, and unusual language use.