Testing the additive and interactive relations of personality and physical indicators of formidability with externalizing behaviors

• Largely null formidability relations with externalizing once gender is accounted for. • Personality relations with externalizing behaviors outweigh physical formidability. • Largely null interactive relations between personality and physical formidability. Personality and formidability are distinct frameworks used to understand the individual differences in engaging in externalizing behaviors. However, these literatures are largely siloed. This study integrated both to examine the additive and interactive relations of personality and physical indicators of formidability with externalizing behaviors in young adulthood ( N = 1,196; Human Connectome Project). Overall, the average associations of Agreeableness, Conscientiousness, and Neuroticism with externalizing behaviors greatly outweighed those of physical indicators of formidability, which were mostly null or negligible. Moreover, the interactive relations between the two constructs were almost uniformly null. While physical indicators of formidability explained little variance in externalizing behaviors above and beyond personality traits, broader measures and diverse samples are needed to clarify these relations.