The Science Of Personality Change - Christian Jarrett

Jarrett defines personality as long-term patterns of thinking, feeling, and relating, best captured by the Big Five (openness, conscientiousness, extraversion, agreeableness, neuroticism). Popular systems like Myers-Briggs are engaging but unreliable—people often get different results on different days—so they’re poor guides for real change.

Traits are partly genetic (around 50% of variance) and correlate with objective biology, so they aren’t just ‘mindset’. Yet long-term studies show nearly everyone changes on at least one major trait over decades. Think of personality as slow to turn but steerable with sustained effort and environmental shifts.

Behaviors like sleep quality, smoking, exercise, and diet don’t just affect health; longitudinal data links them to later shifts in neuroticism, conscientiousness, openness, and extraversion. Good habits tend to pull you upward (more stable, more disciplined); bad ones nudge traits in the opposite direction over time.

Highly conscientious people don’t necessarily have superhuman self-control; they arrange life to avoid temptation in the first place. You can copy this by restructuring your environment, routines, and social circle to reduce friction for good behaviors and increase friction for bad ones.

Research shows people who see effort as energizing (not depleting) maintain more self-control; cultures teaching that discipline is strengthening exhibit less ‘ego depletion’. Adopting the view that using willpower generates more willpower can measurably improve persistence and self-regulation.