Intelligence Testing and the Potential of Autistic People

Do the people who seek to measure the intelligence of autistic people need to get out of our heads?


Rose Eveleth has written an important article for the Scientific American about the hidden potential of autistic people and intelligence testing:

Researchers have long considered the majority of those affected by autism to be mentally retarded. Although the numbers cited vary, they generally fall between 70 to 80 percent of the affected population. But when Meredyth Edelson, a researcher at Willamette University, went looking for the source of those statistics, she was surprised that she could not find anything conclusive. Many of the conclusions were based on intelligence tests that tend to overestimate disability in autistic people. "Our knowledge is based on pretty bad data," she says. 


The intelligence of autistic people is especially likely to be underestimated if it is tested by highly verbal instruments like the Wechsler Intelligence Scale for Children (WISC).  The subject is something Eveleth knows a great deal about because of her autistic brothers.  Her brother Decker was unable to finish an intelligence test based on verbal skills:

This year, as part of the test, the woman delivering the questions asked him, "You find out someone is getting married. What is an appropriate question to ask them?"

My brother's answer: "What kind of cake are you having?"

The proctor shook her head. No, she said, that's not a correct answer. Try again. He furrowed his brow in the way we have all learned to be wary of—it is the face that happens before he starts to shut down—and said, "I don't have another question. That's what I would ask." And that was that. He would not provide her another question, and she would not move on without one. He failed that question and never finished the test.


In order to accurately estimate the intelligence of autistic people, it's essential to use a test like Raven's Progressive Matrices, which does not emphasize verbal skills:

The average child will score around the same percentile for all these tests, both verbal and nonverbal. But an autistic child will not. Isabelle Soullieres, a researcher at Harvard University, gave a group of autistics both WISC and the Raven test to measure the difference between the two groups. Although she expected a difference, she was surprised at just how big the gap was. On average, autistic students performed 30 percentile points better on the Raven test than on WISC. Some kids jumped 70 percentile points. "Depending on which test you use, you get a very different picture of the potential of the kids," she says. Other studies have confirmed this gap, although they found a smaller jump between tests.


Intelligence testing issue can be a very painful and confusing issue for autistic people.  Some of the smartest people I know score very low on a test like the WISC.  I score in the low-average range for tests like the Raven and very high on verbally based tests.  I'm not smarter than them, and I know this for a fact.  We just have different kinds of brains.

Anyway, this is one of the best articles that's been published about autism this year, and you should read the whole thing.