We think personality is far more permanent than it really is. A 2026 study comparing public beliefs with eight longitudinal datasets covering 166,971 people found that people underestimated average Big Five changes in 90% of year-to-year comparisons—and every comparison spanning ages 15 to 90.

A comparison of public beliefs with eight longitudinal panels found that average Big Five personality change was repeatedly underestimated, although the headline's 90% requires care.