Myers-Briggs Type Indicator - Validity

Validity

The statistical validity of the MBTI as a psychometric instrument has been the subject of criticism. It has been estimated that between a third and a half of the published material on the MBTI has been produced for conferences of the Center for the Application of Psychological Type (which provides training in the MBTI) or as papers in the Journal of Psychological Type (which is edited by Myers-Briggs advocates). It has been argued that this reflects a lack of critical scrutiny.

For example, some researchers expected that scores would show a bimodal distribution with peaks near the ends of the scales, but found that scores on the individual subscales were actually distributed in a centrally peaked manner similar to a normal distribution. A cut-off exists at the center of the subscale such that a score on one side is classified as one type, and a score on the other side as the opposite type. This fails to support the concept of type: the norm is for people to lie near the middle of the subscale. "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 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."

In 1991, the National Academy of Sciences committee reviewed data from MBTI research studies and concluded that only the I-E scale has high correlations with comparable scales of other instruments and low correlations with instruments designed to assess different concepts, showing strong validity. In contrast, the S-N and T-F scales show relatively weak validity. The 1991 review committee concluded at the time there was "not sufficient, well-designed research to justify the use of the MBTI in career counseling programs". However, this study also based its measurement of validity on "criterion-related validity (i.e., does the MBTI predict specific outcomes related to interpersonal relations or career success/job performance?)." The ethical guidelines of the MBTI assessment stress that the MBTI type "does not imply excellence, competence, or natural ability, only what is preferred." The 2009 MBTI Form M Manual Supplement states, "An instrument is said to be valid when it measures what it has been designed to measure (Ghiselli, Campbell, & Zedeck, 1981; Murphy & Davidshofer, 2005)." Studies have found that the MBTI scores compare favorably to other assessments with respect to evidence of convergent validity, divergent validity, construct validity, internal consistency, and test-retest reliability.

The accuracy of the MBTI depends on honest self-reporting by the person tested. Unlike some personality measures, such as the Minnesota Multiphasic Personality Inventory or the Personality Assessment Inventory, the MBTI does not use validity scales to assess exaggerated or socially desirable responses. As a result, individuals motivated to do so can fake their responses, and one study found that the MBTI judgment/perception dimension correlates with the Eysenck Personality Questionnaire lie scale. If respondents "fear they have something to lose, they may answer as they assume they should." However, the MBTI ethical guidelines state, "It is unethical and in many cases illegal to require job applicants to take the Indicator if the results will be used to screen out applicants." The intent of the MBTI is to provide "a framework for understanding individual differences, and … a dynamic model of individual development".

The terminology of the MBTI has been criticized as being very "vague and general" as to allow any kind of behavior to fit any personality type, which may result in the Forer effect, where individuals give a high rating to a positive description that supposedly applies specifically to them. Others argue that while the MBTI type descriptions are brief, they are also distinctive and precise. Some theorists, such as David Keirsey, have expanded on the MBTI descriptions, providing even greater detail. For instance, Keirsey's descriptions of his four temperaments, which he correlated with the sixteen MBTI personality types, show how the temperaments differ in terms of language use, intellectual orientation, educational and vocational interests, social orientation, self-image, personal values, social roles, and characteristic hand gestures.

With regard to factor analysis, one study of 1291 college-aged students found six different factors instead of the four used in the MBTI. In other studies, researchers found that the JP and the SN scales correlate with one another.

According to Hans Eysenck: "The main dimension in the MBTI is called E-I, or extraversion-introversion; this is mostly a sociability scale, corelating quite well with the MMPI social introversion scale (negatively) and the Eysenck Extraversion scale (positively) (Eysenck and Eysenck, 1985). Unfortunately, the scale also has a loading on neuroticism, which correlates with the introverted end. Thus introversion correlates roughly (i.e. averaging values for males and females) -.44 with dominance, -.24 with aggression, +.37 with abasement, +.46 with counselling readiness, -.52 with self-confidence, -.36 with personal adjustment, and -.45 with empathy. The failure of the scale to disentangle Introversion and Neuroticism (in fact there is no scale for neurotic and other psychopathological attricutes in the MBTI) is its worst feature, only equalled by the failure to use factor analysis in order to test the arrangement of items in the scale."