Constitutionally-based individual differences in emotional, motor, and attentional reactivity, and self-regulation. More generally, it is person’s characteristic disposition, or style of approaching and reacting to people and situations.
See Childhood Behaviour Questionnaire (CBQ), Extraversion, Five factor model, Goodness-of-fit (psychology), Impulsiveness, Impulsivity, New York Longitudinal Study (NYLS), Neuroticism, Oppositional defiant disorder (ODD), Personality, Surgency