Child-directed speech as a potential source of phonetic precursor enhancement in sound change: Evidence from Cantonese

Phonetically natural sound changes are often assumed to have articulatory, auditory, perceptual, or aerodynamic origins. Any account of sound change must reckon with enhancement of phonetic precursors in order to account for the emergence of categorical sound patterns. Recent studies have advocated viewing child-directed speech (CDS) as a form of hyperspeech. From the perspective of sound change, the child’s phonetic inputs, skewed by the enhancing characteristics of CDS, might led the child’s own production to reflect those enhanced features. To investigate the role of the linguistic inputs to child language acquisition as a potential engine of enhancement that propels (or hinders) sound change, we examined the production of 26 Hong Kong Cantonese-speaking mothers when speaking to their children and to another adult. While well-established sound changes in progress exhibit a “reversal to standard” pattern in CDS, gradient phonetic variation not only is not reduced in CDS, but, in some mothers’ cases, the variation is amplified.