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There's a popular belief that couples gradually develop matching personalities after spending years together.
Large studies have found considerable personality similarity between partners, but evidence suggests much of it may result from people selecting somewhat similar partners in the first place rather than dramatically converging over time.
Partners can certainly influence each other's habits, routines, language, and experiences.
But dating someone for twenty years doesn't necessarily transform two different personalities into one.
Couples can grow together without becoming psychologically identical.
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