The most popular of the group is the Myers-Briggs Type Indicator, roughly based on Dr. Carl Jung’s psychology, which since the 1960s has sorted some 50 million subjects into introvert or extrovert, sensing or intuiting, thinking or feeling and judging or perceiving. Along the way, it has spawned dating sites, couples therapy, diet services, spinoffs for your pet and some backlash.

Adam Grant, professor of organizational psychology at the University of Pennsylvania, said there’s a concerning lack of evidence for the test’s accuracy. “The Myers-Briggs is like asking people what do you like more: shoelaces or earrings?” he said. “You tend to infer that there’s going to be an ‘aha!’ even though it’s not a valid question.” Dr. Grant has tested both as an INTJ and ESFP. It “creates the illusion of expertise about psychology,” he said.

Even Dr. Jung, whose work inspired the test, acknowledged the limitations of type. “There is no such thing as a pure extrovert or a pure introvert,” he wrote. “Such a man would be in the lunatic asylum.”

Where Y’All Sitting?

Personality testing is now a $500 million industry, with growth rates estimated at 10 to 15 percent annually, and appeal to consulting firms, hedge funds and start-ups alike. At McKinsey & Company, incoming associates discover their Myers-Briggs profile within days of coming aboard; at Bridgewater, the test is often administered during the application or onboarding process.

“The Color Code ” assessment was created by Dr. Hartman, a psychologist from Salt Lake City, Utah, in his self-published 1987 book of the same name, which he said has sold hundreds of thousands of copies. It bills itself as “the most accurate, comprehensive and easy to use personality test available.”

For Mr. Shapiro and some of his colleagues, it became something of a religion. “The color code helped me figure out my relationship with my mother,” he said. “It helped me figure out why dating certain girls was easier than others. To this day I still think about it in my relationships.”