Autism has widespread effects, besides affecting how people relate to others, according to a recent study.
Researchers from the Collaborative Program of Excellence in Autism compared 56 children with autism of the age group eight to 15, with 56 who did not have the condition.
It was found that those with autism were found to have more problems with complex tasks, like tying their shoelaces, which suggests that many areas of the brain were affected.
A UK autism expert said the Child Neuropsychology study demonstrated how pervasive the condition was.
Autistic people have long been identified by their difficulties in interacting with others as well as with verbal and non-verbal communication.
In addition they can display repetitive behaviors and have very focused interests.
This study has shown that autism can affect memory, sensory perception and movement because it prevents different parts of the brain working together to achieve complex tasks.
All autistic children had the ability to speak, read and write. However while these performed as well as, and sometimes even better than, the other children in basic tests, they all had trouble with complex tasks.
As a result in the visual and spatial skills tests, autistic children were good at finding small objects in a busy picture, such as finding the character Waldo in the "Where's Waldo" picture books series. However when asked to differentiate between similar-looking people, they found it very difficult.
Spelling and grammar was also easy for these children but they found it quite difficult to understand complex figures of speech, such as idioms. Autistic children also appeared to have problems with their handwriting.
Lead researcher, Nancy Minshew, a specialist in psychiatry and neurology at the University of Pittsburgh School of medicine said, 'These findings show that you cannot compartmentalize autism. It's much more complex.'
According to her researchers investigating autism should therefore look for causes that affect multiple brain areas, rather than simply looking at areas related to communication and repetitive behaviors or obsessive interests.
Dr Minshew added: "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."
Previous studies by the team have revealed through brain scans, that people with autism have abnormalities in the neurological wiring through which brain areas communicate.
She said these abnormalities were the most likely explanation for why the children with autism in the current study had problems with complex tasks but did well in tasks that only required one region of the brain.
Professor Simon Baron Cohen, head of the Autism Research Centre in Cambridge, said: "This new study is important in highlighting atypical functioning in both social and non-social domains, by people with autism spectrum conditions.
"Previously the social difficulties have received a great deal of research attention.
"But this new study reminds us that the causes of autism have more pervasive effects."