Are you a 4 or a 9? Maybe you're a 7.

If you have any idea what those numbers mean, you've likely already encountered the Enneagram, whether it was during an office team-building session or in an excruciating dinner party conversation.

If that question reads as total nonsense to you, don't worry. Someone in your life will almost certainly force you to take the test soon.

The Enneagram is the latest in a long line of personality tests and types to penetrate the zeitgeist. From Hogwarts houses to horoscopes, human beings are hard-wired to categorize ourselves and one another, three personality psychologists told Insider.

"Archetypes and typologies are really attractive to people," John D. Mayer, a professor of psychology at the University of New Hampshire, told Insider. 

But while astrology assigns people personality traits based on their relationship to the planets, the Enneagram claims to go a step further, not only offering users a catchy character description, but promising people the tools to self-optimize at a moment when everyone is eager to hack personal growth.

. . .

Categorizing people is a trend that the field of psychology is increasingly moving away from, Robin Edelstein, a professor of personality psychology at the University of Michigan, told Insider. Human beings are complex and forcing them into one of nine types eliminates nuance and simplifies how we think about ourselves and approach our relationships with others, Rutledge said. 

Personality psychologists have also raised concerns about the money-making ventures spawned by the Enneagram and its counterparts, including pricey workshops, classes, and official tests marketed by experts and influencers who have managed to make these models their livelihood. From corporate leadership trainings to Enneagram-focused parenting sessions, these "coaches" can charge hundreds of dollars for a couple of hours of Enneagram work.

"I think that's what rubs a lot of academic psychologists the wrong way," said Edelstein. "It's not in the spirit of what we do."

Read the complete article in Insider on MSN