Exploring together: Dyadic coordination in object exploration and its role in early lexical development in preterm and full-term toddlers

BACKGROUND: Early language development emerges from the dynamic integration of sensorimotor experiences and caregiver-child interaction. The present study investigated how toddlers' manual object exploration and caregivers' behaviors jointly relate to early lexical development within a dyadic framework, comparing full-term (FT) and preterm (PT) toddlers at 18 months of age. METHODS: Sixty-four dyads of 18-month-old toddlers and their parent (36 FT, 28 PT) participated in a semi-structured play session involving familiar and unfamiliar objects while the interaction was video-recorded using both head-mounted and external cameras. Toddlers' expressive vocabulary was assessed using the Italian version of the MacArthur-Bates Communicative Development Inventories. Micro-analytic coding captured toddlers and caregivers' manual object exploration, and caregivers' labelling. RESULTS: Expressive vocabulary was associated with differences in toddlers' exploratory behaviors. Across groups, toddlers with higher vocabulary showed greater sensitivity to object familiarity, displaying more frequent manipulation of familiar objects. Within the PT group, toddlers with higher vocabulary spent longer exploring objects compared with both lower-performing PT peers and FT toddlers. Caregivers' verbal input differed across groups: caregivers of PT toddlers with lower vocabulary produced more object labels and more contingent labeling during toddlers' manipulation, suggesting an implicit increased verbal scaffolding strategy. CONCLUSIONS: These findings highlight the importance of considering early language development as an embodied and relational process emerging from coordinated exploratory and communicative behaviors within caregiver-toddler dyads, particularly in contexts of developmental risk such as prematurity.