Investigating Speech Perception and Individual Variation in Cognitive-Behavioural Traits

Abstract

Autism Spectrum Disorder (ASD) is a neurodevelopmental condition associated with differences in cognition, communication and language processing. These differences may be explained by their distinct cognitive and perceptual processing styles compared to those of neurotypical individuals. Previous studies have shown that individual differences in traits linked to autism, as measured by the Autism Spectrum Quotient (AQ), influence speech perception and the ability to adapt to contextual variability in speech signals (Stewart & Ota, 2008; Yu, 2010). The present study examined how variation in AQ traits is associated with behavioural and neural responses to ambiguous speech sounds. Fifty-two participants completed a two-alternative forced choice (2AFC) task, categorizing a continuum of fricative sounds between /s/ and /ʃ/ in different vowel contexts (/a/ and /u/). Electroencephalography (EEG) was also recorded during a passive oddball paradigm to measure mismatch negativity (MMN) brain responses to such vowel-fricative-vowel syllables. Results from the behavioural task showed strong categorical perception across participants, with vowel context reliably influencing categorization patterns. Comparison of the highest and lowest AQ quartiles showed that Low AQ participants categorized stimuli more often as /ʃ/ overall. Analysis of the 50% cross over point (PSE) indicated that High AQ participants shifted toward /ʃ/ earlier than the Low AQ group, particularly in the /u/ context. Neural responses showed that participants exhibited reliable event-related potential (ERP) responses in the MMN time window, although polarity was positive rather than negative. Group-level differences emerged in both ERP amplitude and latency, with High AQ individuals showing stronger but slower responses to stimuli in the /u/ context. These findings highlight how individual differences can shape both perceptual and neural mechanisms of speech processing.