Some children line up toys or objects and become very distressed if these are disturbed. Some children develop intense attachments to odd objects, such as pipe cleaners, batteries, or film canisters. Many children may seem underresponsive or overresponsive to sensory stimuli. Thus, they may be suspected of being deaf or visually impaired. It is common for such young children to be referred for hearing and vision tests.
Some children carry food preferences to extremes, with favored foods eaten to excess.
Many such children are very overactive, yet tend to become less overactive in adolescence. The process of learning and thinking in these children is impaired, most particularly in the capacity for imitation, comprehension of spoken words and gestures, flexibility, inventiveness, learning and applying rules, and using acquired information. Follow-up studies have also shown that retardation present at the time of initial diagnosis tends to persist. Those children with a low IQ show more severely impaired social development. They are more likely to display unusual social responses, such as touching or smelling people, ritualistic behavior, or self-injury.