Developmental trajectories and correlates of executive function in children and adolescents with autism spectrum disorder

Executive function (EF; set of high-order cognitive skills) is a salient neuropsychological impairment present in several samples of children and adolescents with Autism Spectrum Disorder (ASD) and has been linked to ASD’s social outcomes, including Theory of Mind (ToM; ability to infer mental states) and adaptive skills. However, understanding of the development of EF and its contribution to social outcomes in ASD is limited as research to date has rarely employed longitudinal designs while it has mainly focused on cool-cognitive EF, without including the hot-affective EF skills. The present thesis was the first to date to investigate the developmental trends of both hot and cool EF as well as “real-life” EF abilities (as rated by teachers) across childhood and adolescence in ASD and typical development. The EF developmental relations to ToM and adaptive skills were also examined across that broad age span (7-16 years) but a particular longitudinal focus was set on the links between EF and ToM across middle childhood (7-12 years). This original piece of research aimed to shed more light on the nature of the developmental pathway followed in ASD relative to typically developing peers across a broad age range and expand understanding of the neurocognitive impairments in EF that underpin crucial social and behavioural outcomes in middle childhood and adolescence in ASD. Overall, 170 children and adolescents (7-16 years), 91 controls and 79 with ASD, were assessed cross-sectionally. A smaller subgroup of children from the initial sample, aged between 7-12 years (37 controls and 45 with ASD) was followed after one year across middle childhood. Children and adolescents undertook tasks that assessed their cool EF (inhibition, working memory, planning), hot EF (affective decision making, delay discounting), ToM (false belief and mental state/ emotion recognition) and IQ ability at both time points. Teacher ratings of participants’ “real-life” EF abilities and adaptive skills were also obtained at the first time point. It was found for the first time that both cool and hot EF linked with ToM in ASD and controls, with significant developmental improvements for selective cool and hot EF emerging across middle childhood. The expansion of the investigation of the developmental trends to adolescence in ASD revealed mainly a developmental pattern of declines or nonsignificant changes between younger children and adolescents for cool and hot EF (only cool inhibition showed improvements), suggesting that perhaps no dramatic EF changes occur beyond the age of 12 years in ASD. ToM and EF were still associated during adolescence in ASD and typical development. Cool and hot EF presented differentiated cross-sectional developmental trajectories and were found associated only in typical development suggesting that separable cool and hot domains of EF may be apparent in ASD. Finally, the development of “real-life” EF skills was found to also follow a differentiated pattern relative to performancebased, cool and hot EF skills, and only “real-life” but not performance-based EF predicted adaptive skills in ASD and typical development. Generally, with few exceptions (i.e. hot delay discounting), cool and hot EF of children and adolescents with ASD followed a deviant development compared to typically developing peers. The present research emphasised the importance of examining the development of cognitive skills (EF) and their links with behaviour in ASD as it may provide a better understanding of theoretical conceptualisations and inform diagnostic assessment and interventions. The organisation and developmental relationships of hot and cool EF within broad age ranges is a current, open topic of debate that the present thesis addressed. These findings may be crucial in overcoming the limitations of current theories of EF development and lead to a better understanding of the heterogeneity in neurocognitive impairments in ASD.