Non-Verbal Intelligence Is a Better Predictor of Cognitive Flexibility in Low Functioning Adolescents with Autism Compared to Adolescents with Intellectual Developmental Disability

Background: Children and adolescents with Autism Spectrum Disorder (ASD) often have more difficulties with cognitive flexibility compared to their typically developing (TD) peers (Geurts et al., 2004). Cognitive flexibility is part of executive functioning (EF) skills and involves the ability to switch flexibly between mental states and take multiple simultaneous perspectives. Research in TD children has demonstrated that verbal abilities predict and mediate performance on tasks that measure cognitive flexibility both concurrently (Low & Simpson, 2012) and longitudinally (Watson, Painter, & Bornstein, 2001). This relationship is less understood in ASD in part because individuals with ASD rely more on visual rather than verbal abilities when completing executive functioning tasks (Kunda & Goel, 2011), and demonstrate predictive relationships between non-verbal abilities and switching performance (Campbell et.al., 2017).

Objectives: This study examined whether a relationship between non-verbal intelligence and cognitive flexibility exists that is specific to adolescents with ASD and lower cognitive abilities (low-functioning), compared to adolescents with Intellectual Developmental Disability (IDD), who also have comparable EF difficulties (Visser et.al., 2015). Specifically, we explored whether there are differences in the relationships between verbal and non-verbal intelligence and cognitive flexibility between groups, and if non-verbal intelligence can predict cognitive flexibility ability in either groups.

Methods: Fifty-three participants (37 males, 16 females; 12-17 years) with a primary diagnosis of either ASD (n= 20) or IDD (n= 33) completed the Wechsler Abbreviated Scale of Intelligence (WASI-II); all participants had a FSIQ of 70 and below (M_FSIQ= 53.7, SD= 10.4). Verbal and non-verbal intelligence were defined by Verbal Comprehension (VCI) and Perceptual Reasoning (PRI) WASI-II indices, respectively. All participants completed a computerized version of the Wisconsin Card Sorting Task (WCST) to measure cognitive flexibility ability.

Results: No significant group difference between ASD and IDD participants was found on either WCST performance (total correct T-score) or verbal intelligence (VCI score). However, the ASD group scored significantly higher on the non-verbal subtests (PRI: M = 65.6, SD = 15.3) compared to the IDD group (M = 56.6, SD = 9.7), t(51)=2.35, p <.05. A linear regression analyses revealed that verbal intelligence (VCI score) did not predict WCST performance for either the ASD (p = .10) nor IDD groups (p = .11). However, non-verbal intelligence (PRI score) was a significant predictor (R² = 36) of the WCST scores for the ASD group only (p =.005).

Conclusions: Non-verbal intelligence predicted performance on the WCST in a group of lower-functioning adolescents with ASD, but not in the adolescents with IDD. It is important to note that this relationship was present despite similar WCST performance across groups. Our study highlights the unique role of non-verbal intelligence in ASD when explaining cognitive flexibility ability. In addition, the relative non-verbal strength observed in our ASD sample suggests that individuals with ASD may solve cognitive flexibility tasks by relying on their non-verbal abilities.