How Personality Tests Work

Common Criticisms of Personality Tests
Hm, was Jung referring to extraverts and introverts in this quote?  Digital Light Source/UIG via Getty Images
Hm, was Jung referring to extraverts and introverts in this quote?  Digital Light Source/UIG via Getty Images

Psychologists, especially in the academic world, direct a fair amount of criticism toward the MBTI and similar personality tests. The most common criticisms include:

  • They're not based on hard data. Neither Myers nor Briggs had any training or education in psychology, and they developed their ideas and theories intuitively. Even the ideas of Jung, an icon in the field of psychology, are considered to have limited practical value for similar reasons [source: Shulman]. Myers and Briggs eventually collected data at hospitals and universities for the test, and CPP claims that "a simple search on the Center for Applications of Psychological Type's MBTI Bibliography Search reveals nearly 11,000 citations of the MBTI assessment" [source: Segovia]. But a third or more of studies finding evidence in support of the MBTI are funded by CPP or people who otherwise make money through the use of the MBTI, and academic psychologists report that much of the evidence is weak [source: Pittenger, Cunningham].
  • Tirza Shulman, PhD, an instructor at Moraine Park Technical College who specializes in personality studies said, "When academic psychologists who don't work for big MBTI look at it, they don't find much. The issue is compounded by the consistent findings that the MBTI lacks internal validity and reliability, so without that it's really tough to make any sort of case for external validity."
  • The four dichotomies of the MBTI don't exist. The MBTI is a type-based indicator, meaning results are sorted into categories with no acknowledgment of degree. Psychological assessments — as used in psychometrics, or the psychological theory of mental measurement — that are used more frequently in the field of psychology follow a trait-based paradigm, where personality traits fall along a spectrum. When you take the MBTI, your answers fall on either side of the center line. If you answer every single question pertaining to the thinking/feeling dichotomy on the feeling side, you'll get the same result for that dichotomy as someone who answered 11 questions for thinking and 13 questions for feeling. "One of the core assumptions of psychometrics, supported by research, is that traits are on a continuum," Shulman said, "and by forcing people into categories (you are an Introvert or an Extravert, rather than you fall on the introverted side of the continuum, but still have some facets that are more extraverted) it loses a lot of nuance."
  • There are problems with the MBTI's construction. The test relies on self-reporting, which opens up a lot of potential for bias. Also, two of the dichotomies are entangled: Answers on the judging/perceiving scale are correlated with answers on the sensing/intuition scale, which ideally should be separate. And there's an overall lack of precision in describing the various categories, which rely on generally positive terms that subjects are happy to apply to themselves [sources: McRae and Costa, Boyle].

These shortcomings affect other self-report tests and personality inventories that are based on the same model as the MBTI. Generally, psychologists view Big Five personality tests as more reliable. But CPP, the publisher of the Myers-Briggs Type Indicator, has some rebuttals to these criticisms.