Approximate number system processing in school-age children with high-functioning autism: Behavioral and neural...

The approximate number system (ANS) is foundational for mathematical development, but its characteristics and neural mechanisms in children with autism spectrum disorder (ASD) remain unclear. While mathematical difficulties are common in ASD, whether nonsymbolic numerosity processing deficits contribute and how perceptual factors modulate such processing require investigation. This study evaluated the Weak Central Coherence (WCC) and Executive Dysfunction (EDF) accounts of autism by examining whether perceptual grouping (connectedness) differentially affects ANS processing in children with high-functioning autism (HFA) compared to typically developing (TD) peers.

Twenty-nine school-age children (14 HFA, 15 TD), matched on age, IQ, and working memory, completed a dot array comparison task during EEG recording. Numerical ratio and perceptual grouping (connectedness) were manipulated to examine effects on behavioral accuracy and ERP components (N1, P2, P3). This manipulation was designed to evaluate competing theoretical accounts of autism-WCC and EDF-by testing whether perceptual grouping cues differentially modulate ANS processing in HFA versus TD children.

Behaviorally, HFA children showed lower accuracy than TD children, and accuracy was strongly affected by numerical ratio and connectedness. The complementary grouped binomial GLMM additionally indicated a Group × Ratio interaction, with the between-group difference concentrated in the low-ratio (i.e., greater numerical separation and easier discrimination) condition. Neurally, HFA children exhibited enhanced frontal P2 amplitudes specifically during core numerical processing (without connecting lines), suggesting atypical attentional or cognitive control engagement during numerosity estimation. Perceptual grouping modulated early attentional allocation (N1 amplitudes) similarly across groups.

Children with HFA demonstrate impaired behavioral ANS acuity and atypical neural recruitment during nonsymbolic numerosity processing. These findings indicate ANS processing is affected in HFA at both behavioral and neural levels, though not differentially modulated by perceptual grouping. The absence of a significant Group × Connectedness interaction argues against the WCC account. Rather, the overall pattern of reduced ANS accuracy and enhanced P2 responses in HFA is more consistent with an EDF framework, indicating greater neural recruitment during ANS processing. The results provide evidence for inefficient neural processing underlying numerical difficulties in autistic children, with implications for understanding mathematical learning in this population.