What are classic symptoms of autism spectrum disorder?

Varies: Autism disorders occur on a spectrum from fairly mild impairment to very severe. Patients with ASD have problems with social interaction, communication, processing sensory information and intellectual disabilities. For a complete list and more explanation look at the cdc site. http://www.cdc.gov/ncbddd/autism/signs.html.

Often less social: There is not a single type of autism. Every one with this label functions a little differently. But in general each one has some depree of problem with: social skills, empathy, communication, and flexible behavior. The level of disability and combination of problems vary greatly from individual to individual. Some speak normally, others don't speak at all.