Does the Speaker Matter: EEG Evidence on the Influence of Voice Information on Phoneme Learning in Infancy

Infants acquire the sound categories of their native language within the first year of life, despite the lack of invariant acoustic features that define these categories across speakers and contexts. Given infants’ ability to process voice information and their preference for the familiar maternal voice, we investigated whether voice familiarity supports the acquisition of phonemes. Specifically, we tested whether infants learn a difficult native vowel contrast better from a familiar speaker compared to an unfamiliar speaker. During a 5-minute phoneme training, 71 3-month-old German-learning infants were exposed to a difficult native vowel contrast (/ɪ/–/ɛ/), spoken either by a previously familiarized speaker or by an unfamiliar speaker. In the subsequent test phase, measuring the electrophysiological mismatch response, we assessed infants’ ability to differentiate the vowels when spoken by either the training speaker or a novel speaker. Using Bayesian analysis, we found evidence against improved vowel discrimination after training with a familiar speaker. Instead, it was training with an unfamiliar speaker that resulted in facilitated vowel discrimination for a novel speaker at test. Our findings suggest that infants may not necessarily benefit from a familiar speaker during phoneme learning, particularly when the speaker is not a caregiver and thus lacks an emotional connection. Learning from an unfamiliar speaker, however, may enhance generalization across speakers, potentially due to increased attention driven by novelty.