The study highlighted that middle children tend to be "more honest, humble, and agreeable" than their siblings.

Indeed, research on personality development over time indicates that, at least in adulthood, individuals’ comparative ratings on traits such as extroversion, agreeableness, and conscientiousness ...

Five-Factor Theory: Personality Is Based on Biology Using the Big Five traits (or five-factor model) as a foundation, Five-Factor Theory proposes that the development of common personality traits ...