The autism world is full of statistics. People love to talk about prevalence rates, and correlations, and the percentage of autistics that can do this that or the other. It can get a little obsessive at times, though it never fails to bring forth all sorts of interesting data. There is, however, one autism statistic that has always bothered me, yet it’s repeated over and over again as if it’s doctrine. This statistic is the claim that “40% of autistic people are also intellectually disabled.”
You’ll often see this statistic being given in marketing campaigns by some of the not-so-good autism organizations. You’ll see something like “Did you know that 40% of people with autism are also struggling with intellectual disability? Make sure you give a big tax-deductible donation to Our Organization so we can Cure Autism Now!®” This is usually also prefaced with some statistic about how common autism is (I’m going to eventually write a post about these as well) and a few calls to be afraid. This is because fear is a very powerful motivator to get people spend money on a cause. Some big autism organizations have grown to their huge sizes just by using fear rhetoric via statistics like these.
Anyway, back to statistics, the distribution of measured intelligence among autistic people is interesting. For the general population, the line for intelligence, when graphed, makes a nice even bell curve with the average sitting at about a 90 on the 200 point IQ scale. However, in autistic people, both intellectual disability and intellectual giftedness are measured much more often, and so the graph of measured autistic intelligence makes a sort of reverse bell curve, with peaks at both the higher end and lower end of the scale. Apparently, 40% of autistic people have a measured IQ under 70, making them intellectually disabled.
Though, the key word here is measured. I am convinced that this statistic is not an accurate reflection of what the distribution of intelligence actually looks like in autistic people.
Any IQ test that you may take would have been originally designed to test the intelligence of a neurotypical person, and these tests don’t take into account how the neurological differences of an autistic or other neurodiverse person would affect the results of the test. For example, any IQ test requires that the test-taker communicate with the test administrator about what their answers are. Here is a potential first breakdown, as a large part of autism is communication differences. An autistic person may actually be doing well on an IQ test but not able to communicate their answers in a way the administrator understands, or their way of communication may be misinterpreted (and remember, communication abilities do not necessarily correlate with overall intelligence). Or, a neurotypical person might think they’re giving the test in a quiet, distraction-free environment, but really those fluorescent lights are highly distracting or even painful to the autistic person being given the IQ test, and as such, results can be skewed. These are just a few examples of how autism might lead to inaccurate results on an IQ test.
These potential differences aren’t just entirely me speculating either, it’s been known since at least the 1980s that intelligence is notoriously difficult to measure in autistic people. For most people, if they take an IQ test at one point and then take the same test again at a later date, their score should be roughly the same assuming no such events like a traumatic brain injury or substance abuse occur in between. But this is not the case for many autistic people. Some autistic people can take the same IQ test over and over again and score all over the board without any consistency among scores. The same people who admit this are also some of the same people that will put out the 40% number as if it’s hard fact. If you’re seeing so much inconsistency in your data, don’t you think there’s something going on with your measurement techniques?
You can also look to the personal stories of many autistic people to find that so often seemingly low IQ score is the result not of a lack of cognition, but rather by a lack of communication. So often you’ll see autistic people, frequently nonverbal or minimally verbal autistic people, who were measured as being intellectually disabled and went through their whole childhood assumed to be unintelligent. Then, upon learning to better communicate with neurotypical people, often with an AAC device, it is discovered that they weren’t intellectually impaired at all, and actually are highly intelligent. Emma, a minimally-verbal autistic girl who is about my age, writes on her blog (in this post) about how she spent years in special education classrooms in which she was assumed to be unintelligent. It was assumed she could not read because she could not read out loud, when in reality she read just fine but couldn’t make her mouth say the right words. It was assumed she did not understand because she could not communicate what she knew. Emma surprised everyone when she started typing and it was realized that she was actually incredibly intelligent and a phenomenal writer. Stories like these are sometimes treated as though they are some sort of amazing anomaly, but in actuality they are very, very, common. This happens all of the time.
Now, there definitely are autistic people who actually are intellectually disabled (and let me be clear, this in no way makes them lesser people or less deserving of love and acceptance). Intellectual disability probably is much more common in autistic people than in non-autistic people. However, I guesstimate that at least half of autistic people with measured IQs in the ID range do not actually have any intellectual impairments at all. There are intellectually gifted autistics, and there are intellectually disabled autistics, and there are lots of autistics with phenomenally average IQs. But I think you can be fairly certain that any IQ measurements for autistic people may not be completely accurate, and that the percentage of intellectually disabled autistic people is not actually 40%.
If you’re the parent of an autistic child with a low measured IQ, I hope this can give you hope. Just because the doctor says your three-year-old nonverbal child’s measured IQ is 53, that absolutely does not mean that you should give up on your child’s intelligence. Always presume competence. Don’t talk about your child with him in the room as if he cannot understand what you’re saying, do not assume by default that she does not understand something because she can’t express herself in a way you understand, and never close opportunities for your child to grow and develop because you assume they lack the intelligence to take advantage of it. Your child might just surprise you one day. And, if not, that’s OK too. You should love and appreciate your child whether or not they have an intellectual disability, or autism, or anything else.