Infant-directed speech (IDS), also known as "baby talk", is a style of speech used by adults to address infants, characterized by high-pitched, articulated intonation and a simplified lexicon. While ubiquitous across languages and cultures, the neural mechanisms underlying IDS are unknown.
To elucidate these mechanisms, the researchers applied functional magnetic resonance imaging (fMRI) to the brains of 35 first-time parents with preverbal infants and 30 men and women without any parenting experience. Subjects also included 16 mothers with toddlers who spoke two-word utterances and 18 mothers with children in elementary school.
While initially aiming to measure brain activity during active speech, signal disruption caused by head movement prompted the researchers to focus on listening instead, which mirrors similar activation patterns without requiring any motion. Brain scans conducted on subjects listening to recorded IDS revealed that mothers with preverbal infants exhibited increased brain activity in areas of the brain known to govern language. This enhanced activation was not observed in any other group, including mothers of children who had advanced beyond the preverbal stage.
Another brain region signaled a second IDS connection: increased cortical activation was observed in speech-related motor areas of mothers in the same group who scored high on a personality test for extroversion. The results thus expose clear distinctions in how people process and generate IDS, providing the first evidence at the neural level that "baby talk", by acting as a bridge for linguistic transfer from mother to infant, plays a key role in the early stages of language acquisition.