Do you make the cut? Four of history's trickiest entrance exams.

Psychologists are still arguing about the best methods to spot intelligence.

Take intelligence tests issued by IBM, NASA, and the U.S. Army.
Take intelligence tests issued by IBM, NASA, and the U.S. Army.Photographs by Brian Klutch and illustrations by Ted Kinyak

Since the turn of the 20th century, psychologists have tried to pin down what it means to be smart. More than 100 years later, they're still arguing about the best methods to spot intelligence. But that squishiness hasn't stopped organizations from NASA to Mensa from adapting psych assessments into some of the trickiest exams ever to meet the No. 2 pencil. Ready to give 'em a go? Time starts... now.

This article was originally published in the Spring 2018 Intelligence issue of Popular Science.