The consistency of categorization-consistency in speech perception

Listeners generally map continuous acoustic information onto categories in a gradient manner with varying individual differences. Typically, such individual differences in speech categorization have been characterized by the mean slope of the response function, as quantified through the visual analog scaling (VAS) task. However, recent evidence suggests that categorization consistency (trial-by-trial response variability) may be a more robust predictor of real-world outcomes than the mean slope. Despite this, the extent to which these VAS indices represent reliable and stable traits relevant to speech perception remains uncertain. This study investigates the stability and trait-like nature of VAS indices by analyzing VAS responses across a diverse range of speech continua. We also examine the potential associations between differences in speech categorization and broader cognitive differences. American English-speaking adults (n = 68) completed the VAS task, alongside three questionnaires assessing autistic traits, anxiety, and impulsivity. We found that categorization consistency showed stronger correlations across continuum types than the categorization slope. Furthermore, no significant correlations were observed between the VAS indices and broader cognitive factors. These results suggest categorization consistency is a more stable property of individuals over the mean slope, and importantly, it is not an artifact due to higher cognitive factors. Thus, the extent to which listeners are consistent in their speech categorization may provide a more accurate characterization of individual differences in speech perception.