Supplementary file 1_Intelligence and executive functioning in adolescence: comparing autism spectrum disorder and typical development.docx

ObjectiveThis study examined the relationship between intelligence and executive functions (EF) in adolescents with Autism Spectrum Disorder without intellectual disability (ASD-WID), focusing on the roles of IQ level, sex differences, and comparisons with typically developing (TD) peers matched for age and IQ.
MethodsA total of 214 participants (118 ASD, 96 TD; aged 12–18 years) were assessed with the Wisconsin Card Sorting Test (WCST) and the Color Trails Test (CTT) as measures of planning, cognitive flexibility, and attentional switching. Cognitive ability was assessed using the WISC-R or WAIS-R, yielding full-scale IQ and three cognitive factors: Verbal Comprehension, Perceptual Reasoning, and Working Memory/Resistance to Distractors. Four subgroups (ASD/TD × high/low IQ) were created. Because multiple variables deviated from normality, non-parametric statistics were applied, including Mann–Whitney U tests for group comparisons and Spearman’s rho correlations for associations between IQ indices and EF measures.
ResultsNo overall EF differences were found between the ASD and TD groups when matched for age and full-scale IQ. Within the ASD group, higher IQ was associated with better planning and cognitive flexibility on the WCST, but not with attentional switching on the CTT; the same pattern appeared in TD adolescents. High-IQ ASD and high-IQ TD adolescents performed comparably on EF measures, suggesting possible compensatory mechanisms in ASD-WID. In contrast, ASD adolescents with lower IQ showed more perseverative errors than TD peers with similar IQ. Across the entire sample (ASD + TD combined), boys scored higher in perceptual reasoning than girls; however, no sex differences were found when analyses were conducted within the ASD group alone, indicating that the observed effect of sex was driven by the TD subgroup rather than by adolescents with ASD. Perceptual reasoning and non-verbal IQ were the strongest correlates of EF performance.
ConclusionIntelligence—especially perceptual reasoning—plays a key role in EF outcomes in adolescents with and without ASD. High IQ may buffer EF difficulties in ASD-WID, whereas lower IQ is linked to greater executive control difficulties. These findings highlight the need for assessment and interventions tailored to individual cognitive profiles, rather than diagnostic status alone.