Parents Adaptively Adjust Timing and Musical Complexity in Object-Use Demonstrations during Early Triadic Interactions

Early musical interactions play a formative role in structuring infant-caregiver exchanges. However, much of the research on communicative musicality has focused on dyadic formats, overlooking the triadic contexts in which infants engage with adults and objects. This study investigates how the musical structuring of adult object-use demonstrations varies across infancy and how these temporal features adapt over developmental time. Drawing on longitudinal naturalistic observations, we analyzed monthly home recordings of eight adult-infant dyads (infants aged 6–12 months) in Spain. Demonstrations were coded for spatial proximity (distant vs. immediate) and musical complexity (three levels) and analyzed using generalized linear mixed-effects models. Results revealed that adults increasingly employed musically rich demonstrations as infants aged, with Level 3 demonstrations lengthening over time, while simpler forms declined in both frequency and duration. In contrast, moderately complex demonstrations (Level 2) remained brief but became more frequent, suggesting a transitional scaffolding function. These findings highlight how adults dynamically calibrate their actions' temporal and musical features to support infants’ participation within evolving triadic ecologies, offering new insight into the rhythmic architecture of early social cognition.