The researchers found that, across the entire series of tests, the children with autism performed as well as — and in some instances even better than — the other children on measures of basic functioning. Uniformly, however, they had trouble with complex tasks.

For example, regarding visual and spatial skills, the children with autism were very good at finding small objects in a cluttered visual field, on tasks like finding Waldo in the ?Where?s Waldo? picture books series. However, when asked to perform a complex task, like telling the difference between the faces of similar looking people, they had great difficulty.

Although their memory for the detail in a story was phenomenal, the children with autism had great difficulty comprehending the story. Many were highly proficient at spelling and had a good command of grammar, but had difficulty understanding complex figures of speech, like idioms and metaphors.

?We see this with our patients,? Dr. Minshew said. ?If you use an expression like ?hop to it,? a child with autism may literally hop.?

Other complex tasks were also difficult for them. The children with autism either had poor handwriting, or wrote very slowly. Many had difficulty tying their shoes and with using scissors.

?These findings show that you can?t compartmentalize autism under three basic areas,? Dr. Minshew said. ?It?s much more complex than that.?

Dr. Minshew explained that the major implication of the finding is that when seeking to understand autism, researchers need to look for a cause or causes that affect multiple brain areas, rather than limiting their search to brain areas dealing with the three characteristic behaviors involving social interactions, communication, and repetitive behaviors or obsessive interests.

?Our paper strongly suggests that autism is not primarily a disorder of social interaction, but a global disorder affecting how the brain processes the information it receives — especially when the information becomes complicated.?

In previous research with an imaging technology known as functional magnetic resonance imaging, or fMRI, Dr. Minshew and her coworkers determined that adults with autism have abnormalities in the neurological wiring through which brain areas communicate. In those studies, the researchers found that people with autism had difficulty performing certain complex tasks that involved brain areas working together. (This research is described in previous releases, http://www.nichd.nih.gov/new/releases/final_autism.cfm, and http://www.nichd.nih.gov/new/releases/autism_brain_structure.cfm.)

Dr. Minshew said that such abnormalities in brain circuitry provide the most likely explanation for why the children with autism in the current study have difficulty with complex tasks that require coordination among brain regions but do well on tasks that require only one region of the brain at a time.