The validity (statistical validity and test validity) of the MBTI as a psychometric instrument has been the subject of much criticism.
It has been estimated that between a third and a half of the published material on the MBTI has been produced for the special conferences of the Center for the Application of Psychological Type (which provide the training in the MBTI, and are funded by sales of the MBTI) or as papers in the Journal of Psychological Type (which is edited and supported by Myers–Briggs advocates and by sales of the indicator). It has been argued that this reflects a lack of critical scrutiny. Many of the studies that endorse MBTI are methodologically weak or unscientific. A 1996 review by Gardner and Martinko concluded: “It is clear that efforts to detect simplistic linkages between type preferences and managerial effectiveness have been disappointing. Indeed, given the mixed quality of research and the inconsistent findings, no definitive conclusion regarding these relationships can be drawn.”
Psychometric specialist Robert Hogan wrote: “Most personality psychologists regard the MBTI as little more than an elaborate Chinese fortune cookie …”
The test and all those of its kind, are categorized in medical journals as one of many self-discovery ‘fads’. That owes its sustained popularity and is categorized together as within the same class of suggestion of ‘which chakra or zodiac sign is dominant’, with the “tests” use of binary questioning and the similar popularity of the MBPT, as akin to all others such as the related ‘9 Enneagram of Personality types’ as each relying on the exploitation of the Barnum effect, a mix of flattery, followed by confirmation bias, with the participants thereby proceeding to searchingly attempt to ‘fit the prediction’.
No evidence for dichotomies
As described in the § Four dichotomies section, Isabel Myers considered the direction of the preference (for example, E vs. I) to be more important than the degree of the preference. Statistically, this would mean that scores on each MBTI scale would show a bimodal distribution with most people scoring near the ends of the scales, thus dividing people into either, e.g., an extraverted or an introverted psychological type. However, most studies have found that scores on the individual scales were actually distributed in a centrally peaked manner, similar to a normal distribution, indicating that the majority of people were actually in the middle of the scale and were thus neither clearly introverted nor extraverted. Most personality traits do show a normal distribution of scores from low to high, with about 15% of people at the low end, about 15% at the high end and the majority of people in the middle ranges. But in order for the MBTI to be scored, a cut-off line is used at the middle of each scale and all those scoring below the line are classified as a low type and those scoring above the line are given the opposite type. Thus, psychometric assessment research fails to support the concept of type, but rather shows that most people lie near the middle of a continuous curve. “Although we do not conclude that the absence of bimodality necessarily proves that the MBTI developers’ theory-based assumption of categorical “types” of personality is invalid, the absence of empirical bimodality in IRT-based research of MBTI scores does indeed remove a potentially powerful line of evidence that was previously available to “type” advocates to cite in defense of their position.”
No evidence for “dynamic” type stack
Some MBTI supporters argue that the application of type dynamics to MBTI (e.g. where inferred “dominant” or “auxiliary” functions like Se / “Extraverted Sensing” or Ni / “Introverted Intuition” are presumed to exist) is a logical category error that has little empirical evidence backing it. Instead, they argue that Myers Briggs validity as a psychometric tool is highest when each type category is viewed independently as a dichoto