Do Measures of Crystallized Intelligence Lie on ASD?

Background: The study of Inspection Time (IT) tasks in relation with intelligence measures has been intriguing researchers since the early 70’s. It is now known that this relation fluctuates around a correlation of -0.5. To date, only two studies have addressed this relation in autism.  Scheuffgen et al (2000) showed that, despite low measure IQ  - as measured by the Wechsler Scales - children with autism performed as good or better than age-matched controls in the IT task. Following these results, Wallace et al (2009) corroborated the lack of relation between IT and IQ but not the superiority of IT in ASD, concluding that this difference may be more pronounced in the low end of the spectrum.

Objectives: The question of untapped cognitive potential is perhaps particularly important for low functioning individuals with ASD.  In an attempt to replicate the Schueffgen et al study in a sample of individuals with autism and severe intellectual impairment, the present study aimed to examine the relation (or lack of) between IT and IQ in autism. In particular, it was hypothesized that participants with ASD and low measured IQ would show faster speed of processing than participants with low measured IQ but not ASD.

Methods: 47 participants with Intellectual Disability (ID) and 33 participants with ASD and additional ID between the ages of 6 and 19 completed both the Raven’s Coloured Progressive Matrices (CPM) and a visual IT task. Both tasks were adapted in order to accommodate the low level of ability in participant groups.

Results: Preliminary results show that the ASD group performed faster at the IT task than the ID group, however this difference was not significant. After comparing groups matched by mental-age, the difference remained non-significant. Contrary to expectations, a significant relationship between IT and intellectual ability (CPM raw scores) were found in both the ASD and the ID groups.

Conclusions: These findings support the hypothesis proposed by Scheuffgen et al (2000); who state that individuals with ASD have an intact basic processing mechanism (as in Anderson’s model of minimal cognitive architecture) or “g”, but that low measured IQ scores result from a failure in theory of mind mechanisms, impeding them to access information through social means. In our study, the social and communicative constrains were reduced by using a measure of pure fluid intelligence. These results could imply a future difference in the way the low end of the autistic spectrum is conceptualized and assessed.