Caregivers fine-tune their speech to support children’s word learning during shared book reading

• Scaffolding and word learning from print and digital shared reading are examined. • Caregivers provide fewer verbal scaffolds for words their child already knows. • This modulation of verbal scaffolds (fine-tuning) predicts children’s word learning. • Caregivers do not adjust their use of gestures to the child's word knowledge. • Verbal and gestural scaffolds are reduced in digital-based shared book reading. The current study investigated whether caregivers adapt their communication to their child’s individual lexical knowledge (fine-tuning) and whether such modulations facilitate children’s word learning during shared book reading. It also examined the influence of book format (print vs. digital) on caregivers’ communicative behaviours. English-speaking dyads ( N = 78; Child M age = 57.74 months) were videorecorded during shared reading sessions with a print and a digital storybook. Caregivers’ use of verbal and gestural scaffolds in relation to target words embedded in the storybooks was coded offline. Before the session, caregivers completed a vocabulary checklist to assess their child’s knowledge of the target words. After the session, children’s word learning was assessed using picture naming, definition, and comprehension tasks. Generalized Linear Mixed Models indicated that caregivers adjusted their verbal, but not gestural, scaffolds to their child’s reported lexical knowledge. This verbal fine-tuning predicted children’s word learning, as assessed through a definition task. Overall, caregivers provided significantly fewer scaffolds in the digital compared to the print format. Theoretical and practical implications of these findings are discussed in light of contemporary literacy practices.