Inhibitory control and math abilities in autism spectrum disorder and typical development

Abstract The general aim of the present dissertation is to investigate inhibitory processes and math abilities in people with autism spectrum disorder (ASD), as compared to typically developing (TD) participants. Understanding the cognitive and academic strengths and weaknesses of students with ASD is crucial for education, quality of life and future outcomes. However, these areas of research are still not fully developed. The first study of the current dissertation (Chapter 2) aimed to advance our understanding of inhibitory control in autism, adopting a meta-analytic multilevel approach. Specifically, this meta-analysis aimed to estimate potential differences between the two groups in inhibitory processes and better understand the significant moderating roles of various sources of heterogeneity. Both measures and participant characteristics were analyzed as possible moderators, for direct and indirect inhibitory measures. The first meta-analysis, on 164 studies adopting direct measures, indicated a significant small-to-medium (g=0.484) deficit in the group with ASD (n=5,140) compared with controls (n=6,075). Similar effect sizes between response inhibition and interference control were found, but they were differentially affected by intellectual functioning and age. The second meta-analysis, on 24 studies using indirect measures, revealed a large deficit (g=1.334) in the group with ASD (n=985) compared with controls (n=1,300). Presentation format, intellectual functioning, and age were significant moderators. The effect of comorbidity with ADHD was not statistically significant. Implications are discussed for IC research and practice in autism. The second study (Chapter 3) of this dissertation focused on previous literature about math abilities in participants with ASD, adopting a meta-analytic approach to estimate potential differences and identify moderating variables. Studies focusing on math abilities in autism are limited and often provide inconsistent results and therefore the meta-analysis was conducted to investigate math abilities in people with ASD compared to TD participants. According with PRISMA guidelines, a systematic search strategy was adopted. First, 4405 records were identified through database searching; then, the title-abstract screening led to the identification of 58 potentially relevant studies and, finally, after the full-text screening, 13 studies were included. Results shows that the group with ASD (n=533) performed lower than the TD group (n=525) with a small-to-medium effect (g=0.49). The effect size was not moderated by task-related characteristics. Instead, sample-related characteristics, specifically age, verbal intellectual functioning, and working memory, were significant moderators. This meta-analysis shows that people with ASD have poorer math skills than their TD peers, suggesting the importance of investigating math abilities in autism, taking into account the role of moderating variables. In the third study of this dissertation (Chapter 4), both inhibitory processes and math abilities were investigated in a sample of participants with ASD (N = 33), as compared to a TD group (N = 60). The first part of the study examined inhibitory processes in detail, considering both response inhibition and interference control measures. Additionally, the study explored the role of possible mediators in explaining differences between groups, such as basic cognitive processes and working memory. Concerning inhibitory control, results showed a poorer performance of the group with ASD in two of the four tasks used: the Matching Familiar Figures task (MFFT), mainly adopted to measure response inhibition, and the Flanker task, mainly adopted to measure interference control. Mediation analyses showed that basic cognitive processes partially mediated group differences on both tasks, whereas working memory partially explained group differences on MFFT. Moreover, group differences were also found in visuospatial working memory, whereas no difference in verbal working memory was found after controlling for vocabulary effect. The second part of the study compared the two groups on different math tasks, assessing specific types of math knowledge. Furthermore, the study investigated the unique contribution of cognitive predictors (vocabulary, response inhibition, interference control, verbal and visuospatial working memory) to specific math abilities and explored whether the association between cognitive predictors and specific math abilities varied between the group with ASD and the TD group. Results showed that the group with ASD showed lower scores on all specific math measures; cognitive processes differently contributed to diverse math abilities, and vocabulary and verbal working memory were stronger associated to specific math abilities in the group with ASD than in the TD group. Findings showed that in general the group with ASD encounters more difficulties in both cognitive processes and math abilities, highlighting some of the factors underlying these differences. Implications for research and clinical assessment intervention were discussed.