LAUSR

Objective: Parent-training interventions to reduce behavior problems in young children typically coach parents on the content of their speech, but rarely assess parents’ prosody during parent–child interactions. Infant-directed speech helps shape the parent–infant relationship and promote language development, which predicts adaptive behavioral outcomes in children. The current study examined (a) the effect of a parent-training intervention on parents’ vocal cues in interactions with their infant and (b) whether parental prosody mediated the impact of the intervention on infant language production. Method: Sixty families with 12- to 15-month-old infants (47% female; 95% of Hispanic/Latino ethnicity) participated in the Infant Behavior Program (IBP), a brief home-based adaptation of Parent–Child Interaction Therapy, or received standard pediatric care. Speech analysis was performed on mothers’ (n = 40) utterances during infant-led play pre- and postintervention. Infants’ number of utterances spoken during play was assessed at pre- and postintervention, and at 3- and 6-month follow-ups. Results: Mothers who received the IBP spoke with greater pitch range and slower tempo postintervention, when controlling for baseline prosody. Change in these vocal cues, which are typical of infant-directed speech, mediated the effect of the intervention on infants’ word production after 6 months. Conclusions: Interventions targeting the content of parents’ speech during parent–infant interactions may lead to changes in parental prosody, which may be beneficial for infants’ language development. Impaired linguistic abilities in infancy are strongly associated with behavior problems in later childhood; thus, these findings highlight a potential mechanism for intervention efficacy in promoting positive socioemotional and behavioral outcomes.