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Understanding autism
Understanding autism

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6.1 Intellectual ability

Differences in cognition, that is, in thinking, learning and problem-solving skills are often represented in terms of Intelligence Quotient (IQ). This is a standardised way of measuring intelligence using tests of both verbal and non-verbal ability. The IQ of people with autism ranges from scores of 70 and below, which corresponds to a profound intellectual disability, to 100, which is the average IQ for any population, to 130 and above, which corresponds to high or extremely high IQ.

A graph showing the average distribution of IQ scores.
Figure 8 The characteristic bell-shaped distribution of IQ scores within the general population. Most people’s IQ scores fall within the range 70 to 130. A minority of individuals have scores lower than 70 or higher than 130.

When a person has profound intellectual disabilities, as defined by an IQ of less than 70, their autism has sometimes been described as ‘low-functioning’. This indicates that the person is profoundly affected, with overt speech and language problems, possibly being non-verbal even into adulthood. Autism in a person with an IQ of 70 or above has often been described as ‘high-functioning’. But this is misleading in several ways. Firstly, IQ scores in the range 70–99 are still below average; a person with an IQ of 85, for instance, may struggle with academic tasks. Secondly, ‘high-functioning’ might suggest that the person is not profoundly affected by their autistic symptoms. But social difficulties and repetitive behaviours can be profoundly disabling at any level of intellectual ability. For instance, an academically able autistic person may struggle to understand instructions or questions from teachers, especially if these are phrased in abstract language. They may find their learning environment stressful due to loud noise, bright lights and unusual smells, and they may expend considerable cognitive resources in ‘pretending to be normal’. Consequently, even with a high IQ, a person’s capacity to learn and thrive academically may be hampered by these additional factors. Alternatively, an academically successful person may find everyday tasks very challenging, as expressed here by Dr Wenn Lawson, writer, psychologist and autism advocate:

I have very uneven skills. This is another one of those enigmas. I have University degrees, I am married and I have three grown children. However, I have huge problems with being disorganised, getting lost, using public transport, understanding others, and just the practical interactions of social situations. I think many of you might be saying ‘So what, I do as well.’ I know that neural-typical individuals might have issues in these areas but I would suggest to you that it is the degree of the ‘issue’ that separates us. How many of you need to sit down on the path outside of a supermarket and do breathing exercises because they have changed the tinned soup isle?!

Lawson, 2018