What is the MBTI? The 16 personality types and the science

The MBTI, or Myers-Briggs Type Indicator, is a personality questionnaire that sorts people into one of 16 types, each named by four letters such as INTJ or ESFP. It was built in the 1940s by Katharine Cook Briggs and her daughter Isabel Briggs Myers from Carl Jung's ideas about psychological types. Millions take it for work and self-reflection, while most research psychologists measure personality a different way, with the Big Five.

In short

• The MBTI asks which side of four pairs you prefer, then combines the four answers into one of 16 types.
• Its critics' main point is that personality varies on a smooth scale, so splitting each scale in half puts near-identical people into opposite types.
• The Big Five, which scores five traits on continuous scales, is the model personality research mostly uses, and it overlaps with four of the MBTI's letters.

What do the four letters of the MBTI mean?

Each letter is one side of a pair, which the test calls a preference. The Myers & Briggs Foundation describes them this way:

Pair	What it asks about	The two sides
E or I	Where you direct your energy	Extraversion: the outer world of people and activity. Introversion: your inner world of ideas
S or N	How you take in information	Sensing: concrete facts and details. Intuition: patterns and the big picture
T or F	How you decide	Thinking: logic and consistency. Feeling: people and values
J or P	How you deal with the outside world	Judging: plans and closure. Perceiving: staying open and flexible

Two choices in each of four pairs give 2 × 2 × 2 × 2 = 16 combinations. Someone who comes out Introverted, Intuitive, Thinking and Judging is an INTJ; someone Extraverted, Sensing, Feeling and Perceiving is an ESFP. The words carry narrower meanings than in everyday speech. "Judging" doesn't mean judgmental, and "Feeling" doesn't mean emotional. The foundation itself says the test "sorts for preferences; it does not measure traits, ability, skill, or character."

Where did the MBTI come from?

Briggs started studying personality around 1917. When Jung's book Psychological Types appeared in English in 1923, she adopted its framework: Jung had proposed that people differ in attitude (extraversion or introversion) and in favored mental functions (sensation, intuition, thinking, feeling). Jung himself developed the ideas from clinical observation, not from tests.

Myers turned them into a questionnaire during the Second World War, with the aim of helping people find work that suited them. Neither woman had formal training in psychology or test design. Her first handbook appeared in 1944. The Educational Testing Service took the test on in 1962, when the first MBTI manual was published, and the rights passed to Consulting Psychologists Press in 1975, now The Myers-Briggs Company. Its publisher has said that as many as 2 million assessments are given each year.

What do psychologists criticize about it?

The central problem is the split. Type theory says people fall into one camp or the other, but on each MBTI scale most people score near the middle, not at the ends. If scores bunched at two ends, as type theory predicts, a cut-off in the middle would cut through empty space. Instead, studies find roughly bell-shaped distributions, so the cut-off falls where people are most crowded.

A worked example shows what that does. Imagine a scale from 0 to 60 where 30 is the cut-off and anything above means Extraversion. Ana scores 31 and Ben scores 29. They answered almost every question alike, yet one is labeled E and the other I, and their reports describe opposite people. Carla scores 58. She and Ana get the same letter, though Carla differs from Ana far more than Ben does. A trait score would keep all three numbers and show Ana and Ben as near neighbors.

That also explains the retest results. Someone near the middle can cross the line on a different day, after a different night's sleep. Studies cited in Wikipedia's summary of MBTI research found that between 39% and 76% of people got a different type when they retook the test after only five weeks. The publisher's 2018 manual, as the Myers & Briggs Foundation reports it, gives test-retest correlations of 0.81 to 0.86 for the four scales among 1,721 adults retested 6 to 15 weeks apart. That is respectable, but those numbers measure how stable the underlying scores are, not how often the four-letter type stays the same.

The third criticism is about use. A 1991 committee of the US National Research Council, reviewing the test in In the Mind's Eye, found good construct validity for the E–I scale and relatively weak validity for the S–N and T–F scales. It called the test's popularity "in the absence of proven scientific worth" troublesome, and said better studies would be needed to justify its use in career counseling. It isn't designed to predict job performance, and its publisher's own guidance is not to use it to select job candidates.

Still argued

Supporters, including the test's publisher, argue that types are a useful language for talking about differences, that the scales are reliable by the usual 0.70 standard, and that people find their profiles accurate. Critics such as the psychologists Randy Stein and Alexander Swan (2019) answer that the theory behind the types clashes with what is known about personality and is hard to test, and others note that people tend to rate vague profiles as accurate whatever their source, the so-called Barnum effect. What both sides tend to accept is that the scores carry real information and that the 16 boxes lose some of it.

What are the Big Five personality traits?

The Big Five, also called the five-factor model, is the framework most personality research uses. It came out of studies of the words people use to describe each other, which kept boiling down to five broad dimensions. The textbook Psychology 2e calls it the most popular theory in personality psychology. The five are often remembered as OCEAN: openness to experience, conscientiousness, extraversion, agreeableness and neuroticism, the tendency to feel anxiety and other negative emotions.

The key difference is that each trait is a score, not a category. Nobody is "an extravert" in the Big Five; they sit at some point on the extraversion scale, and most people sit near the middle of each. The traits stay fairly stable over adulthood, with small shifts: conscientiousness and agreeableness tend to rise with age, neuroticism to fall.

	MBTI	Big Five
Output	One of 16 types	Five scores on continuous scales
Built from	Jung's clinical theory	Statistical analysis of how people describe each other
Measures emotional stability	No	Yes, as neuroticism
Main use	Self-reflection, team workshops, coaching	Research, and some clinical and workplace assessment

The two overlap more than their fans might expect. In a 1989 study of 468 adults aged 19 to 93, the psychologists Robert McCrae and Paul Costa found that MBTI scales lined up strongly with four Big Five traits: E–I with extraversion, S–N with openness, and more modestly T–F with agreeableness and J–P with conscientiousness. They found no support for true types, and concluded the test measures four fairly independent dimensions. The Big Five's fifth trait, neuroticism, has no MBTI letter at all.

Is the MBTI useless, then?

Not useless, but often oversold. Much of what it measures is real, and talking about preferences can help a team see why one person wants a plan agreed in advance and another wants to keep options open. The trouble starts when a four-letter label is treated as a fixed identity, or as a reason someone can or can't do a job. Personality is one part of what psychology studies, and like an IQ score, a personality result describes tendencies on average, not limits on a person.

A useful habit is to read a profile the way critical thinking reads any claim: ask what it would predict, and whether a description would fit almost anyone. Traits like these are, in the end, patterns in how a brain tends to respond to people and situations, and those patterns vary by degree.

Check yourself

• Without looking back: why does a cut-off in the middle of a scale cause trouble for people who score near it?
• What is the main difference between a type and a trait?
• Which Big Five trait has no counterpart among the MBTI's four letters, and what does it describe?

Sources

• MBTI basics — The Myers & Briggs Foundation
• Validity and reliability of the MBTI instrument — The Myers & Briggs Foundation
• Psychological Types, by C. G. Jung — Classics in the History of Psychology, York University, 1921 (English 1923)
• In the Mind's Eye: Enhancing Human Performance — National Research Council, National Academies Press, 1991
• Trait theorists, in Psychology 2e — OpenStax, Rice University
• Myers–Briggs Type Indicator — Wikipedia