Speech categorization consistency is robustly associated with receptive oral language performance

Speech perception research on individual differences and clinical populations has traditionally emphasized the gradient/categorical dimension of categorization. Recent work, however, highlights categorization consistency-trial-by-trial response variability-as a more informative index of individual differences. Whether this index is relevant for language functions remains unknown. Across three experiments, we tested whether speech categorization consistency, rather than gradiency, was associated with receptive oral language ability. In Experiment 1, English-speaking adults (n = 57) completed a speech visual analog scaling task, rating a speech continuum on a continuous scale, alongside two language assessments. Greater consistency in speech categorization was strongly associated with better receptive oral language performance, whereas gradiency showed no such relationship. Experiment 2 (n = 76) added a visual analog scaling task in which participants performed the same task with a visual continuum to determine whether the observed effects reflected domain-general categorization mechanisms. Speech consistency again showed a strong association with language ability, and commonality analyses indicated that this effect was largely unique to speech, not to visual consistency. Experiment 3 (n = 95) equated the number of speech and visual continua and added a nonverbal IQ measure. Despite shared variance across domains, speech categorization consistency retained a unique association with language performance beyond visual categorization consistency and nonverbal IQ. These findings suggest that categorization consistency reflects both domain-general and speech-specific components, with speech consistency showing the most robust relationship to receptive oral language performance. This reframes individual differences in speech categorization by highlighting categorization consistency as an important dimension linking perceptual processing and broader language function. (PsycInfo Database Record (c) 2026 APA, all rights reserved).