Ecologically Valid Assessment of Infant Physical Aggression: A Pilot Feasibility Study

Physical aggression (PA) in infancy represents an important area of study for understanding the development of externalizing behaviors. Current methodologies for assessing infant PA rely primarily on parent‐report measures or brief structured laboratory observations, each with inherent limitations. This pilot feasibility study ( N = 31) evaluated a multi‐day, home‐based observation protocol for capturing infant PA in children aged 11–24 months using wearable and stationary cameras across 5 days. Parents recorded an average of 2.5 h/day across 5 days, demonstrating high compliance and successful capture of infant PA. Observed PA occurred more frequently than parent‐reported PA, with modest concordance between methods ( β = 0.24). Nearly half of observed aggression was preceded by conflict, underscoring its contextual relevance. Parent‐reported laxness was associated positively with parent‐reported PA ( r = 0.38). Findings suggest that naturalistic observations provide an ecologically valid assessment approach that captures PA behaviors that may go unreported or unnoticed by parents. This methodology holds promise for improving understanding of early PA development and addresses a gap in the measurement of naturalistic, home‐based observations that capture PA behaviors in ecologically valid contexts.