People with autism may perform unusually well on some tests of visual processing

Feb 7 2005

A new study suggests that people with autism may perform unusually well on some tests of visual processing.

The researchers found that autistic people were less likely than others to have false memories about images they had seen earlier. The researchers had previously demonstrated this kind of effect with verbal material, but not with visual material.

In this case, the results suggest that the autistic people had trouble seeing the images in context – a hallmark of the disorder.

The study's findings point out that the effects of autism may be more general than researchers once thought.

"We thought that the effects of autism might go beyond language problems – that it affects different areas of the brain," said David Beversdorf, a study co-author and an assistant professor of neurology at Ohio State University. In 2000, he led a similar study that looked at the effect of autism on language. "We wanted to see if we'd get similar results with a visual model, and we did."

Beversdorf and his colleagues presented their findings on February 4 in St. Louis at the annual meeting of the International Neuropsychological Society.

The researchers tested a total of 28 adults, 14 of whom were high-functioning autistics – these participants could verbalize their thoughts (people with severe forms of autism often can't or don't speak.)

The researchers showed the autistic and non-autistic participants a series of slides that portrayed images containing groups of geometric shapes. The group then looked at a second set of test slides – two of these slides contained images from the original set, two contained images that were obviously not part of the first set of slides, and one slide contained a “lure” image – an object very similar in shape, size, arrangement and color to the images shown in the original set, but one that wasn't actually part of that set.

The lure image tested what researchers call the "false memory effect" – given this slide's similarity to the original group of slides, most people would believe that they had seen it in the original set. And most of the non-autistic participants mistakenly identified the lure as part of the original group.

Not so with the autistic people, though – they were far less susceptible to the false memory.

"This suggests that autistic people may have trouble with using context," Beversdorf said. "The image on the lure slide was so similar to the images shown in the original group of slides that it was fairly difficult to determine if it was part of the first group.

"Whether they were aware of it or not, the non-autistic people had used the context of the original group of slides – the shape, size and color of these images – to decide if they had previously seen the lure image. This same use of context doesn't seem to happen in the autistic brain, which may relate to the altered brain circuitry in autism."

Beversdorf and his colleagues found similar results in a previous language study. In that research, people were read a list of related words followed by a shorter list that included a lure word. More often than not, the autistic participants said that they had not heard the lure in the original word group, while non-autistic people mistakenly said they had heard it.

"The new study reinforces the results of the language study, but expands it beyond the domain of language," said Ashleigh Hillier, a study co-author and a research scientist in neurology at Ohio State University.

"Autistic people usually can't grasp the full meaning, or context, of a situation," she said. "This often leads to difficulties in social settings, as making inferences from what someone else says or thinks is extremely difficult for an autistic person."

People with milder forms of autism often have IQs that are normal or above normal. But they still struggle in the real world. Understanding the kind of difficulties autistic people have with context may improve their treatment options.

"Our studies strongly suggest that autistic people need more emphasis on and explanation about the context of different situations," said Hillier, who leads a social skills support group for people with milder forms of autism. "We can teach them how to interpret different situations."

Hillier and Beversdorf conducted the study with Heather Campbell, a nursing student at Ohio State; Kate Renner, an undergraduate student at the university; and Nicole Phillips, a former Ohio State medical student.

This study was funded by the National Institutes of Health’s National Institute of Neurological Disorders and Stroke.

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