Although children with autism usually appear physically normal and have good muscle control, odd repetitive motions may set them off from other children. A child might spend hours repeatedly flicking or flapping her fingers or rocking back and forth. Many flail their arms or walk on their toes. Some suddenly freeze in position. Experts call such behaviors stereotypies or self-stimulation.
Some people with autism also tend to repeat certain actions over and over. A child might spend hours lining up pretzel sticks. Or, like Alan, run from room to room turning lights on and off.
Some children with autism develop troublesome fixations with specific objects, which can lead to unhealthy or dangerous behaviors. For example, one child insists on carrying feces from the bathroom into her classroom. Other behaviors are simply startling, humorous, or embarrassing to those around them. One girl, obsessed with digital watches, grabs the arms of strangers to look at their wrists.
For unexplained reasons, people with autism demand consistency in their environment. Many insist on eating the same foods, at the same time, sitting at precisely the same place at the table every day. They may get furious if a picture is tilted on the wall, or wildly upset if their toothbrush has been moved even slightly. A minor change in their routine, like taking a different route to school, may be tremendously upsetting.
Scientists are exploring several possible explanations for such repetitive, obsessive behavior. Perhaps the order and sameness lends some stability in a world of sensory confusion. Perhaps focused behaviors help them to block out painful stimuli. Yet another theory is that these behaviors are linked to the senses that work well or poorly. A child who sniffs everything in sight may be using a stable sense of smell to explore his environment. Or perhaps the reverse is true: he may be trying to stimulate a sense that is dim.
Imaginative play, too, is limited by these repetitive behaviors and obsessions. Most children, as early as age 2, use their imagination to pretend. They create new uses for an object, perhaps using a bowl for a hat. Or they pretend to be someone else, like a mother cooking dinner for her "family" of dolls. In contrast, children with autism rarely pretend. Rather than rocking a doll or rolling a toy car, they may simply hold it, smell it, or spin it for hours on end.