Norwegian parents do not modulate infant-directed speech based on their infants’ attributed word knowledge

Infant-directed speech (IDS), the register caregivers often use when interacting with infants,has been suggested to facilitate language learning. To assess its didactic role, we examinedthe acoustic modifications parents make in IDS for words they attribute to their infant asunknown, versus known, by analysing data from three studies of Norwegian IDS with 8–18-month-old infants (N=132 infants, N=182 parents). Parents’ speech was recorded during ashared-reading interaction with their infant and with an experimenter (as a control register),ensuring that speech content was matched across participants and registers. Contrary to ourhypotheses, we found no evidence that parents emphasised IDS for words attributed asunknown. Furthermore, Bayesian analyses suggested that Norwegian parents do notmodulate IDS based on infants’ attributed word knowledge. Thus, our findings do not supportthe notion that parents use IDS as a didactic strategy to teach individual words, underscoringalternative motivations for engaging in such speech.