Northwestern University psychology professor William Revelle spent years trying to show there are no real personality types. His latest research published Monday in Nature Human Behavior points to the opposite conclusion. Using data from 1.5 million survey respondents, it identifies four clear personality types—average, reserved, self-centered, and role model—based on the character traits of neuroticism, extraversion, openness, agreeableness, and conscientiousness. "I believed there were no types at all," but the data "kept coming up with the same four clusters ... at higher densities than you'd expect by chance," Revelle says in a release. Per Inverse, four predominant combinations of traits emerged regardless of the researcher in charge or survey questions asked.
To check the results, researchers zoned in on teenage boys, whom they referred to as notoriously self-centered, and found them overrepresented in the corresponding personality type, associated with high extraversion but low openness, agreeableness, and conscientiousness. Underrepresented here, females over 15 are more likely than men to be average—highly neurotic and extraverted but not open—or role model, with high scores in all traits but neuroticism. A type isn't fixed, however. As people age, they tend to move away from being self-centered and reserved and toward the role model category, becoming somewhat more agreeable and conscientious, researchers say. Find out your personality type here. (Your walk might give a clue.)