The assessment of the intellectual profile in children with ASD is of a crucial importance. For example, the DSM-5 requires to specify whether ASD is associated with intellectual disability. For this reason, intelligence... [ view full abstract ]
The assessment of the intellectual profile in children with ASD is of a crucial importance. For example, the DSM-5 requires to specify whether ASD is associated with intellectual disability. For this reason, intelligence measures are routinely used for the diagnosis and the assessment of children with autism spectrum disorders (ASD). On this respect, research has shown that up to the 70% of the individuals with ASD present with intellectual impairments. However, the prevalence of intellectual impairments in individuals with ASD is still not clear and it varies considerably across different studies. Several batteries are employed to assess the intellectual profile of children with ASD, but the most prominent is WISC-IV. However, the presence of sharp discrepancies between verbal and non-verbal indexes has led some researchers to argue that WISC-IV might actually underestimate the intellectual functioning of children with ASD, who are often impaired in verbal tasks. In this study we tested 50 children with ASD by using two intelligence batteries WISC-IV and Leiter-3, which is a non-verbal battery for assessing intelligence. The hypothesized i) that WISC-IV underestimates the IQ in children with ASD ii) and that this is particularly true for children with a lower intellectual functioning profile. Results showed that Leiter-3 indexes were higher compared to WISC-IV indexes. In particular, the difference between the two IQs WISC-IV and Leiter-3 was dramatic, F(1, 49) = 89.16, p < .001, η2p = .645. We also directly compared results from the two batteries in the two groups. We performed a 2 groups [HFA and LFA] × 2 batteries [WISC-IV and Leiter-3] mixed ANOVA. The interaction between groups and batteries, F(1, 48) = 29.12, p < .001, η2p = .378, the effect of batteries, F(1, 48) = 163.73, p < .001, η2p = .773, and the effect of groups, F(1, 48) = 86.73, p < .001, η2p = .664, were statistically significant These results clearly indicate that the cognitive profile at WISC-IV was generally lower than that obtained through the Leiter-3, which is consistent with the observation that WISC-IV appears to underestimate the performance of children with ASD. Furthermore, the difference between the two batteries was greater in children with a lower intellectual profile, which confirms that children with a lower functioning profile are severely penalized by the WISC-IV. This paper provides experts and clinicians with important insights on the intellectual functioning of children with autism and with or without intellectual impairments, demonstrating that the way in which intelligence is assessed in these children clearly matters and caution is need in evaluating the intellectual functioning of these children.
