Individuals with congenital amusia do not show context-dependent perception of tonal categories.

Perceptual adaptation is an active cognitive process where listeners re-analyse speech categories based on new contexts/situations/talkers. It involves top-down influences from higher cortical levels on lower-level auditory processes. Individuals with congenital amusia have impaired pitch processing with reduced connectivity between frontal and temporal regions. This study examined whether deficits in amusia would lead to impaired perceptual adaptation in lexical tone perception. Thirteen Mandarin-speaking amusics and 13 controls identified the category of target tones on an 8-step continuum ranging from rising to high-level, either in isolation or in a high-/low-pitched context. For tones with no context, amusics exhibited reduced categorical perception than controls. While controls' lexical tone categorization demonstrated a significant context effect due to perceptual adaptation, amusics showed similar categorization patterns across both contexts. These findings suggest that congenital amusia impacts the extraction of context-dependent tonal categories in speech perception, indicating that perceptual adaptation may depend on listeners' perceptual acuity.