Personality tests are hugely popular, though if you ask working psychologists, they’ll tell you the results are little better than astrological signs. But a new study, based on huge sets of personality data representing 1.5 million people, has persuaded one of the staunchest critics of personality tests to conclude that maybe distinct personality types exist, after all.

In a report published Monday in the journal
Nature Human Behavior, researchers at Northwestern University in Illinois identify four personality types: reserved, role models, average and self-centered.

The new approach was nothing like the basis for widely used personality tests such as the Myers-Briggs, which spits out a personality type with acronyms like INTJ...or ESFP...