Research on Attention Deficit Hyperactivity Disorder (ADHD) has provided insights into autism as a neurocognitive disorder. Individuals with autism often show a great deal of interest in details most of us would only barely notice or ignore. Most of us dining at a restaurant would notice the waiter taking our order, while a person with autism might be fascinated with the lights or tablecloth. This behavior is due to structural abnormalities in certain parts of the brain. Likewise, shifting attention from one object to another requires thinking and memory. While most of us take shifting attention for granted, that ability is difficult for individuals with autism. Children with autism and ADHD have problems shifting or maintaining attention.

Research in the late 1980’s and 1990’s shed light on autism’s many defects in thinking. Rumsey and Hamburger conducted a study demonstrating dramatic impairments in reasoning that were not accounted for by problems in other skills. The study showed that patients with autism had good performance on tests requiring simple language ability and memory, but moderate to severe impairment in more complex thinking tasks. In 1992 Minshew and others showed that autistic patients performed normally on simple memory tests and tests of basic language, such as word fluency, reading, decoding, and spelling. Memory problems were seen with delayed recall, and language problems were demonstrated on tests of more advanced abilities such as comprehension of sayings, metaphors, and unclear sentences. A pattern emerged showing that simple abilities were normal but complex abilities were not. Deficits in the ability to think with language and use language to shift from one thought to another were also identified.

Another study by Minshew and others in 1994-95, compared highly functioning subjects with autism against subjects without autism. On tests of mechanical language skills such as speech, mechanical reading, word recognition, spelling, phonetic analysis, and simple calculation, subjects with autism scored the same or better than controls. On tests of complicated verbal thinking, however, subjects with autism scored much lower.

These results led researchers to devise an expanded set of tests to attempt to find higher order thinking disorders in the brain. The tests included measurements of attention, sensory perception, motor function, language ability, memory, thinking, and the ability to understand the sight of objects and spaces. In simple language tests, individuals with autism scored higher than controls, while controls scored higher than autistic subjects on tests of motor, complex memory, complex language, and thinking categories. Ability to handle the sight of objects and space was normal in all subjects. Neither group showed attention deficits nor was there a significant amount of difficulty with motor function.

Through these studies, researchers were able to develop a characteristic profile of thinking that was common to non-mentally retarded adolescents and adults with autism. The test subjects had trouble forming ideas, performing complicated memory and language tasks, and doing tasks that required skilled motor function. They had normal or even superior functioning in attention, sensory perception, simple memory, simple language, rule-learning, and understanding objects in space.

Interestingly, these findings showed real differences between autism and mental retardation.  Individuals with autism often attain IQ scores in the normal range because they have intact language, memory, arithmetic, rule-learning, and sight-interpreting abilities. People with autism do have lower than average abilities in problem solving, concept formation, complex language and complex memory abilities which accounts for their poor ability to adapt and function in society. Sensory perception is not affected by autism.

In various cognitive domains, patients with autism could perform simple tasks normally but performance on more complex abilities was lacking. Not only was test performance different but this dichotomy between simple and complex tasks could be measured electroencephalograph (EEG). In 1991 and again with colleagues in 1997, Minshew reported that individuals with autism display normal EEG tracings when performing simple tests but abnormal EEG when attempting complex thinking tasks.

This EEG evidence along with structural abnormalities identified later strongly suggests that autism is directly caused by a brain abnormality.

The biological test results fit nicely with the behavioral studies that were performed in patients with autism. Seeking and maintaining eye contact, making and interpreting facial expressions, and understanding humor and complex meanings in communication are certainly higher order language skills. While normal subjects tend to do less well on tests as they become more complicated, the performance of autistic subjects dropped precipitously as information became increasingly complex.

Everyday conversation requires complex information processing requiring high-level memory and thinking skills. Individuals with autism lack many of these skills. In fact it is likely that people without autism are using so many subtle and automatic thinking skills involving language, memory, and handling knowledge in social situations that they have yet to be noticed or described. Through studying individuals with autism we not only learn about the illness but also how the brain normally operates during communication.

---------------------------------------------------------------------------------------------------------

References

Minshew, N. J., & Goldstein, G. (1998). Autism as a disorder or complex information processing. Mental Retardation and Developmental Disabilities Research Reviews, 4, 129-136.

Minshew, N. J., Goldstein, G., & Siegel, D. J. (1997). Neuropsychologic functioning in autism: Profile of a complex information processing disorder. Journal of the International Neuropsychological Society, 3, 303-316.

Rumsey JM, Hamburger SD. Neurophysiological findings in high-functioning men with infantile autism, residual state. J Clin Exp Neuropsychol 1988; 10:201–221.

Author: Karina Poirier, Psy.D., BCBA. Director of Clinical Services, Center for Social Cognition http://www.socialcognitions.com/