Hi everyone and welcome to my letter I post in the #AtoZChallenge. Today, I want to write about IQ. IQ, a measure of intelligence, is one of the determining criteria for intellectual disability. So how is it measured in the general population and in people with an intellectual or developmental disability?
The concept of IQ dates back to the 19th century, when early psychologists first started developing tests for measuring intelligence. These were based on the idea that intelligence increases as a child grows up, so they were based on skill sets a child of a certain age should be able to master. IQ was then decided to be intellectual age divided by chronological age multiplied by 100 (to get the idea that a normal IQ is 100). For example, if a child aged five masters the skills of a three-year-old, their IQ was 3 / 5 * 100 = 60.
This is problematic, because among other things it does not allow for testing of adults and does not allow for variation on different skill levels. It was therefore abandoned in favor of a norm-based IQ testing system. Both the Wechsler scales (most commonly used in Europe) and the Stanford-Binet test (which is used more often in the U.S.), are norm-based, with an IQ of 100 being average and standard deviations of 15 (Wechsler) or 16 (Stanford-Binet) determining differences such as intellectual disability and giftedness.
I am familiar only with the Wechsler scales. There is a preschooler, a children’s and an adult version of these. The children’s and adult versions at least contain non-verbal as well as verbal tasks. Until some years ago, these were divided into categories of verbal and performance IQ. I, for one, can only have my verbal IQ tested. This refers to skills such as math, vocabulary, working memory, information (general knowledge questions), etc. The performance/non-verbal tasks include patterns, object recognition (where you see an object with part of it missing and need to identify it), etc. I am pretty sure that, if my performance IQ could ever be tested, it’d be significantly lower than my verbal IQ, as is commonly the case with verbally capable autistics.
On the other hand, nonspeaking or partly verbal autistics often find their intelligence being underestimated because they struggle on verbal IQ tests or cannot take them at all. For this reason, for nonspeaking autistics, a non-verbal IQ test may be more appropriate.
I did honestly find that the adult Wechsler scale was quite difficult even for me, a person with a high level high school and some college education. I honestly doubt those with a moderate intellectual disability will even be able to answer the simplest of questions on it. For example, the first math question was something like: “John had six apples, Peter had two apples, how many apples did the two of them have combined?” Interestingly, the first vocab question was to define “apple”. And no, in Dutch, there is no ambiguity (in case people are thinking “the brand that makes iPhones”). However, the correct answer was “fruit”, which I struggled to come up with, as that’s not a definition, more like a categorization.