<b>Early joint engagement during caregiver-child interactions: Developmental trajectories in genetic syndromes and caregiver scaffolding strategies</b>

<p dir="ltr">Joint engagement is a dyadic state during caregiver-child interactions where both the child and caregiver are actively involved in shared activities and objects. As joint engagement is often reduced in neurodevelopmental conditions, several caregiver-mediated interventions have been developed to target it, with children exhibiting greater joint engagement when caregivers provide responsive verbal inputs. Yet, there has been limited research on joint engagement in children with genetic syndromes, despite their significant developmental deficits and joint engagement challenges. Additionally, prior studies have focused on coaching caregivers to use verbal strategies to promote joint engagement, with less emphasis on nonverbal strategies. We conducted two studies that included infants and toddlers with Angelman syndrome (AS) and Down syndrome (DS), which differ in functional severity across multiple developmental domains. In the first study, we characterized and compared the developmental trajectories of joint engagement in AS, DS, and typically developing (TD) children. Multilevel analyses showed that coordinated joint engagement developed differently across these groups: AS children exhibited consistently low engagement, while DS and TD children showed similar growth rates, though the initial engagement level in DS was lower than in TD children. In contrast, supported joint engagement developed similarly across groups. In the second study, we examined the unique contributions of verbal and nonverbal strategies in promoting current and future joint engagement. Hierarchical regression analyses revealed that caregivers’ nonverbal matching of toys was significantly associated with children’s current joint engagement and marginally related to future joint engagement. Verbal strategies, however, were unrelated to joint engagement. Overall, our studies suggest that joint engagement develops differently in AS and DS and that nonverbal scaffolding strategies play a critical role in promoting joint engagement in young children. Future research may examine additional genetic syndromes to further advance syndromic-specific, caregiver-mediated interventions of joint engagement for children with genetic syndromes.</p>