Despite the important developmental outcomes associated with effortful control (EC), there is limited research demonstrating the efficacy of early interventions for improving EC and assessing the extent to which a child's level of baseline EC impacts the outcome of intervention on externalizing problems. This study aims to fill these gaps in the literature by assessing the efficacy of the Infant Behavior Program (IBP), a parenting intervention for infants with elevated levels of behavior problems, in improving infant EC and the moderating effect of baseline infant EC on intervention outcomes. Participants included 60 high-risk 12- to 15-month-old infants and their mothers. Families were randomized to receive the IBP or standard pediatric primary care. Parent-report measures of infant behavior and compliance were examined at baseline, post-intervention, and 3- and 6-month follow-up assessments. Results showed infants who received the IBP displayed significantly higher levels of EC at the post-intervention assessment compared to infants in the control group. Additionally, moderation analyses showed initial levels of EC moderated the effect of the IBP on externalizing problems and compliance, such that infants with higher levels of baseline EC displayed greater decreases in externalizing problems at post-intervention and greater increases in compliance at the 6-month follow-up. While these findings did not survive a false discovery rate correction, they offer preliminary support for the efficacy of the IBP in improving infants' EC and highlight the importance of considering EC as a factor associated with early intervention outcomes for externalizing problems.
Keywords: early intervention; effortful control; infancy; parenting intervention; self-regulation.
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