Younger individuals may have little or no interest in establishing friendships. Older individuals may have an interest in friendship but lack understanding of the conventions of social interaction. Often an individual's awareness of others is markedly impaired. The impairment in communication is also marked and sustained and affects both verbal and nonverbal skills. A disturbance in the comprehension of language may be evidenced by an inability to understand simple questions, directions, or jokes.
Imaginative play is often absent or markedly impaired.
These individuals also tend not to engage in the simple imitation games or routines of infancy or early childhood or do so only out of context or in a mechanical way. Individuals with Autistic Disorder have restricted, repetitive, and stereotyped patterns of behavior, interests, and activities. They may line up an exact number of play things in the same manner over and over again or repetitively mimic the actions of a television actor. There is typically no period of unequivocally normal development, although one or two years of relatively normal development has been reported in some instances. In a minority of cases, parents report regression in language development, generally manifested as the cessation of speech after a child has acquired from five to ten words.