The test is scored by evaluating each answer in terms of what it reveals about the taker. Each question is relevant to one of the following cognitive learning styles. Each is not a polar opposite, but a gradual continuum.

The extraverted types learn best by talking and interacting with others. By interacting with the physical world, extraverts can process and make sense of new information. The introverted types prefer quiet reflection and privacy. Information processing occurs for introverts as they explore ideas and concepts internally.

The second continuum reflects what people focus their attention on. Sensing types enjoy a learning environment in which the material is presented in a detailed and sequential manner. Sensing types often attend to what is occurring in the present and can move to the abstract after they have established a concrete experience. Intuitive types prefer a learning atmosphere in which an emphasis is placed on meaning and associations. Insight is valued higher than careful observation, and pattern recognition occurs naturally for intuitive types.

The third continuum reflects a person's decision preferences. Thinking types desire objective truth and logical principles and are natural at deductive reasoning. Feeling types place an emphasis on issues and causes that can be personalized while they consider other people's motives.

The fourth continuum reflects how a person regards complexity. Judging types will thrive when information is organized and structured, and they will be motivated to complete assignments in order to gain closure. Perceiving types will flourish in a flexible learning environment in which they are stimulated by new and exciting ideas. Judging types like to be on time while perceiving types may be late and/or procrastinate.

David W. Keirsey mapped four "temperaments" to the existing Myers–Briggs system groupings: SP, SJ, NF, and NT; this often results in confusion of the two theories. However, the Keirsey Temperament Sorter is not directly associated with the official Myers–Briggs Type Indicator. 

McCrae and Costa based their Five Factor Model (FFM) on Goldberg's Big Five theory.  McCrae and Costa present correlations between the MBTI scales and the currently popular Big Five personality constructs measured, for example, by the NEO-PI-R.  The five purported personality constructs have been labeled: extraversion, openness, agreeableness, conscientiousness, and neuroticism (emotional instability), although there is not universal agreement on the Big Five theory and the related Five-Factor Model (FFM).  The following study is based on the results from 267 men followed as part of a longitudinal study of aging. (Similar results were obtained with 201 women.)

These results suggest that the four MBTI scales can be incorporated within the Big Five personality trait constructs, but that the MBTI lacks a measure for emotional stability dimension of the Big Five (though the TDI, discussed above, has addressed that dimension). Emotional stability (or neuroticism) is a predictor of depression and anxiety disorders. These correlations refer to the second letter shown, i.e., the table shows that I and P have negative correlations with extraversion and conscientiousness, respectively, while F and N have positive correlations with agreeableness and openness, respectively.

These findings led McCrae and Costa to conclude that, "correlational analyses showed that the four MBTI indices did measure aspects of four of the five major dimensions of normal personality. The five-factor model provides an alternative basis for interpreting MBTI findings within a broader, more commonly shared conceptual framework." However, "there was no support for the view that the MBTI measures truly dichotomous preferences or qualitatively distinct types, instead, the instrument measures four relatively independent dimensions.

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 ..." 

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 extroverted 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 extroverted. 

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." 

The content of the MBTI scales is problematic. In 1991, a 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".  This study 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?)."  

There is insufficient evidence to make claims about utility, particularly of the four-letter type derived from a person's responses to the MBTI items. 

The accuracy of the MBTI depends on honest self-reporting. :52–53 Unlike some personality questionnaires, such as the 16PF Questionnaire, 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 weakly with the Eysenck Personality Questionnaire lie scale.  If respondents "fear they have something to lose, they may answer as they assume they should." :53 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",  so as to allow any kind of behavior to fit any personality type, which may result in the Forer effect, where people 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. :14–15 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. :32–207

Researchers have reported that the JP and the SN scales correlate with one another.  One factor-analytic study based on (N=1291) college-aged students found six different factors instead of the four purported dimensions, thereby raising doubts as to the construct validity of the MBTI. 

According to Hans Eysenck: "The main dimension in the MBTI is called E-I, or extraversion-introversion; this is mostly a sociability scale, correlating quite well with the MMPI social introversion scale (negatively) and the Eysenck Extraversion scale (positively).  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 counseling readiness, -.52 with self-confidence, -.36 with personal adjustment, and -.45 with empathy. 

The failure of the scale to disentangle Introversion and Neuroticism (there is no scale for neurotic and other psychopathological attributes in the MBTI) is its worst feature, only equaled by the failure to use factor analysis in order to test the arrangement of items in the scale." 

The test-retest reliability of the MBTI tends to be low. Large numbers of people (between 39% and 76% of respondents) obtain different type classifications when retaking the indicator after only five weeks.  In Fortune Magazine (May 15, 2013), an article titled "Have we all been duped by the Myers-Briggs Test" stated:

Within each dichotomy scale, as measured on Form G, about 83% of categorizations remain the same when people are retested within nine months and around 75% when retested after nine months. 

About 50% of people re-administered the MBTI within nine months remain the same overall type and 36% the same type after more than nine months.  For Form M (the most current form of the MBTI instrument), the MBTI Manual reports that these scores are higher (p. 163, Table 8.6).

In one study, when people were asked to compare their preferred type to that assigned by the MBTI assessment, only half of the people chose the same profile. 

It has been argued that criticisms regarding the MBTI mostly come down to questions regarding the validity of its origins, not questions regarding the validity of the MBTI's usefulness.  Others argue that the MBTI can be a reliable measurement of personality; it just so happens that "like all measures, the MBTI yields scores that are dependent on sample characteristics and testing conditions". 

Isabel Myers claimed that the proportion of different personality types varied by choice of career or course of study. :40–51  However, researchers examining the proportions of each type within varying professions report that the proportion of MBTI types within each occupation is close to that within a random sample of the population.  

Some researchers have expressed reservations about the relevance of type to job satisfaction, as well as concerns about the potential misuse of the instrument in labeling people. 

CPP became the exclusive publisher of the MBTI in 1975. 

They call it "the world's most widely used personality assessment", with as many as two million assessments administered annually.  CPP and other proponents state that the indicator meets or exceeds the reliability of other psychological instruments and cite reports of individual behavior.  

Although meta-analysis claim support for validity and reliability,   studies suggest that the MBTI "lacks convincing validity data" and that it is pseudoscience. 

The MBTI is not a useful predictor of job performance.  As noted above under Precepts and ethics, the MBTI measures preferences, not ability. 

The use of the MBTI as a predictor of job success is expressly discouraged in the Manual. :78 However, the MBTI continues to be popular because many people lack psychometric sophistication, it is not difficult to understand, and there are many supporting books, websites and other sources which are readily available to the general public.