Patterns of Mean-Level Change in Personality Traits Across the Life Course: A Meta-Analysis of Longitudinal Studies

The question

Do personality traits actually change, on average, as people age — and if so, which ones, when, and by how much?

The method

A meta-analysis of 92 longitudinal samples tracking mean-level change in the Big Five traits across the life course [1].

The findings

Conscientiousness rises measurably in adulthood, most in the 20s and 30s (d = .22 from ages 20–30, d = .26 from 30–40, both statistically significant) [1]. Social dominance — the assertive, take-charge facet of extraversion — shows the largest gains, climbing through the teens and twenties (d = .20 at 10–18, .41 at 18–22, .28 at 22–30) and cumulating to over one full standard deviation of change across young adulthood [1]. Emotional stability rises in small steps across the teens, twenties, and thirties [1]. Two traits run the other way: social vitality (the second facet of extraversion) and openness to experience rise in adolescence but then decline in old age; agreeableness barely moves until old age, when it rises [1].

The limits

These are group averages built by stitching together many separate studies at different ages, not one cohort tracked from birth to death — the authors describe the resulting life-course trajectory as an upper-bound estimate, since no single longitudinal study has followed the same people that long [1]. The changes, while statistically real, are modest in absolute size — a fraction of a standard deviation per decade for most traits.

• When you pass on an otherwise promising candidate because they read as undisciplined or unreliable today: conscientiousness is exactly the trait shown to rise through the 20s and 30s [1] — someone can still grow into the reliability the role needs, not just be scored on it as a fixed quantity now.
• When a young hire seems to lack the assertiveness or “take charge” quality a role needs: social dominance is the trait that grows fastest and furthest of anything measured here across young adulthood [1] — don’t mistake early-career reticence for a permanent ceiling on it.