Is That You I Hear? Speaker Familiarity Modulates Neural Signatures of Lexical-semantic Activation in 18-month-old Infants

Developmental language studies have shown that lexical-semantic organization develops between 18 and 24 months of age in monolingual infants. In the present study, we aimed to examine whether voice familiarity facilitates lexical-semantic activation in the infant brain. We recorded the brain activity of 18-month-old, French-learning infants using EEG while they listened to taxonomically related and unrelated spoken word pairs by one voice with which they were familiarized with before the experiment, and one voice with which they were not familiarized. The ERPs were measured in response to related and unrelated target words. Our results showed an N400 effect (greater amplitudes for unrelated as opposed to related target words) over the left hemisphere, only for the familiar voice, suggesting that the voice familiarity facilitated lexical-semantic activation. For unfamiliar voices, we observed an earlier congruence effect (greater amplitudes for related than for unrelated target words). This suggests that although 18-month-olds process lexical-semantic information from unfamiliar speakers, their neural signatures of lexical-semantic processing are less mature. Our results show that even in the absence of personal relation with a speaker, familiarity with a voice augments infant lexical-semantic processing. This supports the idea that extralinguistic information plays a role in infant lexical-semantic activation.