If you’ve ever visited a career counselor, you may already be familiar with the Myers-Briggs Type Indicator, or MBTI. It was created by a mother-daughter team in the 1940s. Myers and Briggs were not psychologists, but they had read “Psychological Types” by Carl Jung, and they wanted to show how everyone could fit into one of the personality types that Jung had described.

The indicator divides people according to four binary factors, for a total of sixteen types. The MBTI website describes the factors thusly:

  • Introversion/Extroversion — Do you prefer to focus on the outer world or your own inner world?
  • Sensing/Intuition — Do you prefer to focus on the basic information you take in or do you prefer to interpret and add meaning?
  • Thinking/Feeling — When making decisions, do you prefer to first look at logic and consistency or first look at the people and special circumstances?
  • Judging/Perceiving — In dealing with the outside world, do you prefer to get things decided or do you prefer to stay open to new information and options?

Looking at these factors, you can see why so many people take this test when they are in college, or when they are considering a career move. While many people spend their whole lives in careers that aren’t obvious matches for their personalities, you’re most likely to be happy and successful in a job that suits you. An introvert may be advised to seek out behind-the-scenes jobs, while extroverts are pushed towards public-facing roles. Judging types are good project managers, but they may struggle in jobs that require investigation or information-gathering.

So, is finding a great candidate as easy as giving applicants a test? Not so fast. The MBTI was never meant to be scientific, and throughout the years, plenty of psychologists have criticized it as imprecise. Even Carl Jung, on whose theories the indicator was based, disagreed with the idea that people broke down into easy binaries; he thought of personality as more of a spectrum. This is probably why many people who take the test twice get different results. Asked to decide between two options when they really fall in between, they choose randomly. However, if all you want to do is narrow down your job search, the MBTI is a good place to start. If the suggested careers sound all wrong for you, then don’t go into those careers.

With that in mind, it’s easy to see why it’s a bad idea to predicate hiring or promotion decisions on a personality test. You may miss out on perfectly qualified candidates because of the way they answered a question. And it’s legally dubious — forcing employees or applicants to take a personality test may violate privacy laws.

A completely foolproof way to divide people up by personality would make life a lot easier for managers and job seekers alike. Alas, the Myers-Briggs test is not that. It should only be treated as a rough guide to a career path.