One hypothesis about why there are so many more boys and men on the autism spectrum than there are girls and women is that boys and men, for whatever reason, are more likely to get diagnoses of autism spectrum conditions.
One of the reasons commonly put forward by people (including me) making this argument is that the diagnostic criteria reflect a picture of autism derived disproportionately from autistic boys and men, and autistic girls and women differ sufficiently from their male counterparts in their abilities, behavior, developmental histories etc. to ensure that they will often fail to meet those criteria.
While browsing PLOS ONE I found a couple of recent-ish articles looking into what those differences might be.
The more recent study, just published this week, involved giving four largish groups of participants (one autistic and one neurotypical group within each sex, with each group having thirty-two people in it) a battery of tests designed to measure five different skills: theory of mind, emotion recognition, executive functioning, perceptual attention to detail, and manual dexterity.
What are all those things and how would you go about measuring them? Well, the first of those skills, theory of mind --- also called cognitive empathy or mind-reading --- is one I've written a lot about on this blog. I've also written a lot (usually in the same posts) about the tool psychologists seem to use most of the time to assess this skill in adults: the Reading the Mind in the Eyes Test. I don't think I need to say anything more about either the skill or the test; the test is relatively straightforward, a series of black-and-white photographs of faces, cropped to show only the eyes, paired with a choice of four emotion words. You are supposed to guess which of the words best describes what the person whose eyes are in the photograph is feeling.
I listed theory of mind and emotion recognition separately, even though the Reading the Mind in the Eyes Test obviously involves both. There's another test the researchers used, one that they describe as a test of emotion recognition, that reads to me like it's almost the same thing as the Reading the Mind in the Eyes Test, only it uses pictures of entire faces instead of just eyes. It's called the Karolinska Directed Emotional Faces Test.
To test the participants' executive-functioning abilities, the researchers used something called the Go/No Go Task. This involves pressing buttons on a computer keyboard in response to certain cues appearing on the computer screen; in this study the cues were arrows pointing either to the right or to the left. (Right and left were each associated with a different target key: P for right and Q for left. So the people taking the test were literally minding their P's and Q's!) The test also includes extraneous cues that test takers are not supposed to respond to. So what's being tested is not just one's ability to hit a key when a light goes on; it's also one's ability to restrain one's key-hitting impulse when something close to, but not exactly like, the target stimulus appears.
There were some other things the researchers included under the umbrella of executive functioning: working memory (tested by having the participants repeat nonsense syllables), word generativity (ability to come up with lots of words beginning with the same letter in a short amount of time) and motor planning, which they tested using the Assembly subtest of the Purdue Pegboard Test. (This involves putting simple objects together in a set order using whatever hand they tell you to use.) This obviously assesses manual dexterity as well as the ability to figure out what you need to do in what order (i.e., motor planning), although they also had the participants complete the other parts of the Purdue Pegboard Test to test manual dexterity alone.
Finally, the test they used to measure attention to detail was the Embedded Figures Test, which I've also blogged about before, noting that autistic people have shown a particular aptitude for this task.
The results are mostly unsurprising: the autistic study participants did worse at both of the facial-expression-interpreting tasks, and also at pressing the right key in the Go/No Go task. On the two language-related memory tasks, they performed no differently than the control group. (This is not surprising given that all of the participants are described as "high-functioning," having average-to-above-average IQs (about 115, plus or minus about 15 points) with verbal IQ greater than or equal to performance IQ).
The emotion-recognition data get more interesting when you look more closely at them, though; apparently the autistic study participants had more trouble identifying some emotions than others. Fear was the one it took them longest to recognize; it was also the hardest one for the non-autistic people to identify, too, but the gap between the two groups' average reaction times is the biggest in this category. It took the autistic study participants, on average, somewhere between four and five seconds (closer to five) to identify the fearful faces. For the non-autistic participants, it took maybe three and a half seconds. Happy faces were the easiest for both groups to identify, and the difference between groups was only half a second compared to the 1-1.5 second gap in their response times to fearful faces. All the other reaction times are clustered within a relatively narrow range for both groups: between 2.5 and 3 seconds for the autistic group, and between 2 and 2.5 for the control group. So, even though fear was tricky for everyone, it proved especially challenging for the autistic people. The study authors guess that maybe this is because autistic people studiously avoid looking at other people's eyes, and the eyes are apparently the most important cue that someone looks frightened.
There were also a couple of novel findings, too, though. For instance, on the Assembly component of the Purdue Pegboard Test, it was only the autistic men who had any problems relative to their same-sex control group. The autistic women were, you might say, indistinguishable from their peers.
But the most surprising thing, for me, was their results on the Embedded Figures Test. This is a pretty solidly defined Thing Autistic People Are Really Good At, yet in this study, where there was a difference between autistic and non-autistic groups, it was the non-autistic people who found the hidden shape faster. (That was also true for the men and not for the women).
In general, the authors describe a pattern of male and female autistics having more or less the same degree of impairment in what they call the "hallmark" of autism spectrum conditions, which is inability to pick up on another person's nonverbal cues to their mental or emotional states*, but with the autistic men, and not women, also having additional impairments in other domains.
The authors point out that this contradicts what had been conventional wisdom about cognitive sex differences within autism, which held that autistic women were usually more severely disabled than autistic men**.
I haven't forgotten about the other, earlier study; I'm just going to give it its own post so as not to make this one overlong.
Lai, M., Lombardo, M., Ruigrok, A., Chakrabarti, B., Wheelwright, S., Auyeung, B., Allison, C., , ., & Baron-Cohen, S. (2012). Cognition in Males and Females with Autism: Similarities and Differences PLoS ONE, 7 (10) DOI: 10.1371/journal.pone.0047198
*This elusive quality can be called theory of mind, mentalizing, "mind-reading" or empathizing. It may also involve more than one cognitive, emotional or perceptual ability, but this study doesn't really go into that.
**To be REALLY picky, this study doesn't address the issue of intellectual disability, as no one who participated in it would meet the criteria for having ID. This shows that autistic men of slightly above average IQ are more likely to have problems with motor planning and figure disembedding.