Cognitive Assessment, Research Link

No, the WISC-IV doesn’t underestimate the intelligence of children with autism.

The title of a new study asks “Does WISC-IV underestimate the intelligence of autistic children?” The authors’ answer is that it probably does. I believe that the reasoning behind this conclusion is faulty.

This study gives the unwarranted impression that it is a disservice to children with autism to use the WISC-IV. Let me be clear—I want to be helpful to children with autism. I certainly do not wish to do anything that hurts anyone. A naive reading of this article leads us to believe that there is an easy way to avoid causing harm (i.e., use the Raven’s Progressive Matrices test instead of the WISC-IV). In my opinion, acting on this advice does no favors to children with autism and may even result in harm.

Based on the evidence presented in the study, the average score differences between children with and without autism is smaller on Raven’s Progressive Matrices (RPM) and larger on the WISC-IV. The rhetoric of the introduction leaves the reader with the impression that the RPM is a better test of intelligence than the WISC-IV. Once we accept this, it is easy to discount the results of the WISC-IV and focus primarily on the RPM.

There is a seductive undercurrent to the argument: If you advocate for children with autism, don’t you want to show that they are more intelligent rather than less intelligent? Yes, of course! Doesn’t it seem harmful to give a test that will show that children with autism are less intelligent? It certainly seems so!

Such rhetoric reveals a fundamental misunderstanding of what individual intelligence tests like the WISC-IV are designed to do. In the vast majority of settings, they are not for certifying how intelligent a person is (whatever that means!). Their primary purpose is to help psychologists understand what a person can and cannot do. They are designed to help explain what is easy and what is difficult for a person so that appropriate interventions can be selected.

The WISC-IV provides a Full Scale IQ, which gives an overall summary of cognitive functions. However, it also gives more detailed information about various aspects of ability. Here is a graph I constructed from Figure 1 in the paper. In my graph, I converted percentiles to index scores and rearranged the order of the scores to facilitate interpretation.


Average Raven’s Progressive Matrices (RPM) and WISC-IV scores for children with and without autism

It is clear that the difference between the two groups of children is small for the RPM. It is also clear that the difference is also small for the WISC-IV Perceptual Reasoning Index (PRI). Why is this? The RPM and the PRI are both nonverbal measures of logical reasoning (AKA fluid intelligence). Both the WISC-IV and the RPM tell us that, on average, children with autism perform relatively well in this domain. The RPM is a great test, but it has no more to tell us. In contrast, the WISC-IV not only tells us what children with autism, on average, do relatively well, but also what they typically have difficulty with.

It is no surprise that the largest difference is in the Verbal Comprehension Index (VCI), a measure of verbal knowledge and language comprehension. Communication problems are a major component of the definition of autism. If children with autism had performed equally well on the VCI, we would wonder whether the VCI was really measuring what it was supposed to measure. Note that I am not saying that a low score on VCI is a requirement for the diagnosis of autism or that the VCI is the best measure of the kinds of language problems that are characteristic of autism. Rather, I am saying that children with autism, on average, have difficulties with language comprehension and that this difference is manifest to some degree in the WISC-IV scores.

The WISC-IV scores also suggest that, on average, children with autism not only have lower scores in verbal knowledge and comprehension, they are more likely to have other cognitive deficits, including in verbal working memory (as measured by the WMI) and information processing speed (as measured by the PSI).

Thus, as a clinical instrument, the WISC-IV performs its purpose reasonably well. Compared to the RPM, it gives a more complete picture of the kinds of cognitive strengths and weaknesses that are common in children with autism.

If the researchers wish to demonstrate that the WISC-IV truly underestimates the intelligence of children with autism, they would need to show that it underpredicts important life outcomes among this population. For example, suppose we compare children with and without autism who score similarly low on the WISC-IV. If the WISC-IV underestimated the intelligence of children with autism, they would be expected to do better in school than the low-scoring children without autism. Obviously, a sophisticated analysis of this matter would involve a more complex research design, but in principle this is the kind of result that would be needed to show that the WISC-IV is a poor measure of cognitive abilities for children with autism.

Research Link

Short list of bad things associated with high IQ

IQ is positively correlated with almost everything that is good in life and negatively correlated with almost every bad outcome you can think of. The reasons for these correlations are diverse and often surprising.

Though high IQ is generally associated with positive outcomes, it is associated with a few negative ones. It is unknown how many there are but the list is surely very short. Here are some of them:

  1. People with high IQ tend to be nearsighted. The higher the IQ, the more likely the person is going to need glasses. Some stereotypes exist for a reason! Why the association exists is anyone’s guess…and many guesses have been made. The most amusing hypothesis I have found is the idea that big brains squish the eyes! One thing that is clear is that the correlation is not due to excessive reading.
  2. People with high IQ tend to have allergies. Another stereotype! However, the evidence for this finding is somewhat mixed. Perhaps there is some sort of trade-off: You can either distinguish between good and bad foreign particles or you can distinguish between good and bad ideas.
  3. People with high IQ are more likely to commit suicide? The evidence for this finding is mixed and sometimes in the opposite direction, probably because the relationship IQ and suicide is non-linear and moderated by a number of demographic and cultural factors. My guess is that some people who know that they are talented feel worthless when they have failed to live up to expectations (both their own and other people’s).

A new study suggests that this list might get a little longer (sort of). It is well known that IQ and criminality are negatively correlated and that high IQ appears to be associated with lower levels of criminality even among those otherwise at higher risk of becoming criminals. However, a new study by Hampton, Drabick, and Steinberg suggests that, all else equal, high IQ, among people with psychopathic tendencies, is associated with higher levels of criminal offending.

My interpretation of this is that high cognitive ability is neither good nor bad. Rather, it simply allows you do more of what you want to do. In a well-regulated society in which incentives are properly aligned with good behavior, high intelligence will correlate with good behavior. However, in certain contexts (e.g., criminal organizations and dictatorial regimes), high intelligence amplifies one’s capacity to do harm.

Cognitive Assessment, Research Link

Working memory capacity for body movements?

This article is serious. But I think it is fun fun fun!

A test of working memory capacity was developed such that people had to imitate sequences of body movements such as the ones below:

Sample 1
Sample 2
Sample 3

So, participants would be shown such clips in quick succession and then asked to imitate the movements in the same order.

Interestingly, the test is not just a novel way of measuring something we can already measure. It has differential validity. That is, it did not correlate with more traditional measures of visual and verbal working memory but it did correlate with a test measuring understanding of gestures.

I imagine that dancers would do well on such a test for two reasons. First, people who are good at imitating body movements (a la Gardner’s Bodily-Kinesthetic Intelligence) have a natural advantage in learning to dance. Second, dancing gives extensive training in imitating other people’s body movements. Expertise and training matter! Anyway, giving such a test to dancers and non-dancers would be a fun little study to do.

CHC Theory, Research Link

Fluctuations in attention are related to fluid but not crystallized intelligence

Attentional Control and Fluid Intelligence

There are many defensible ways to slice the ability domain. In a previous post, I put fluid intelligence, working memory capacity, and processing speed together in a conceptual grouping called Controlled Attention. I did not do this capriciously but on my review of the available evidence. However, the precise nature of the ways in which these abilities depend on attentional control is still being explored.

In what I consider to be an important paper, Unsworth and McMillan (2014) provide direct evidence that fluid intelligence test performance is related to moment-to-moment fluctuations of one’s attentional state. The paper consists of three experiments designed to tease apart various explanations of the positive correlation between test item performance and self-rated attentional state measured before each item (ranging from 1 = not at all focused on the task to 10 = totally focused on the present task).

Overall findings

  1. Test performance was not negatively affected by having to complete attentional state ratings.
  2. Self-rated attentional state predicted performance on fluid intelligence test items but not on crystallized test items.
  3. Participants with the most variability in self-rated attentional state from item to item performed more poorly on fluid intelligence test items than did people with more stable levels of self-rated attentional state. Thus, attentional control, in accordance with theory, appears to be an important component of fluid intelligence.

One of my suspicions was that is that participants might justify poor perceived performance on a previous item by claiming low levels of attention before the next item. It might be easier on one’s self esteem to claim, “That last item was hard because I am feeling scattered, not because I am not smart.” However, this explanation is undermined by the fact that self-rated attentional state predicted performance on fluid intelligence test items whether the items were in ascending level of difficulty or in random order. Even so, it would have been nice to have seen analyses showing that attentional state predicted performance on the next item more strongly than it “predicts” performance on the previous item.

CHC Theory, Cognitive Assessment, Research Link

Spatial memory and fluid intelligence: A small question answered very well

Siedlecki and Salthouse (2013) have conducted the kind of intelligence research I love to read. In “Using contextual analysis to investigate the nature of spatial memory,” they describe how they had noticed an incidental finding from a previous study that intrigued them and then carefully designed a battery of tests to see if the phenomenon would replicate and withstand several challenges to the original interpretation. It did.

The specific finding is that after accounting for fluid intelligence, spatial memory has no unique relationship with reference markers of verbal memory. This finding is important because it suggests that although it is fine to talk about “memory” as a conceptual category, there may not be an ability called general memory.

The evidence from this paper (and earlier studies) suggests that CHC Theory may need to be amended such that spatial memory and visual memory are distinguished. Furthermore, spatial memory seems to have a special relationship with fluid intelligence, even when fluid intelligence is measured with non-spatial tests.

What l like about this study is that its methodological rigor makes the finding much more persuasive than is the case in most individual differences research. Most studies in this area are from convenience samples and rarely are designed to test highly specific hypotheses.

Cognitive Assessment, Research Link

Delightful article about cloze tests? Yes, delightful I say!

Any article that starts off quoting Mrs. Bennet, my favorite Jane Austen character, is going to catch my eye. This article (published online ahead of print)  really used the quote with great skill and then proceeded to teach me quite a lot that I did not know. Check it out:

Gellert, A. S. & Elbro, C. (2012). Cloze Tests May be Quick, But Are They Dirty? Development and Preliminary Validation of a Cloze Test of Reading Comprehension, Journal of Psychoeducational Assesssment.

Cognitive Assessment, Research Link

Nice summary of phenotypic hallmarks of learning disorders

Table 1 from this article  has a nice summary of phenotypical deficits in people with dysgraphia, dyslexia, and oral and written language disorders:


Automatic legible letter writing

Orthographic coding

Finger succession


Pseudoword reading


Phonological coding

Orthographic coding

Rapid automatic naming


Rapid automatic switching

Oral and Written Language Learning Disability

Morphological coding

Syntax coding

CHC Theory, Research Link

Conspiracy Theories and Crystallized IQ

Agents of the Clandestine World Government posing as researchers have just published this bit of misinformation: People who know what’s really going on know very little! That’s right. This so-called “study” claims that people who believe in “conspiracy theories” (i.e., the truth) have lower crystallized intelligence. Very clever, Clandestine World Government, but we will not be mocked!