Construction of the MBTI^®

Following on from that was the idea that people would be able to report their preferences through using a self report psychological inventory based on Jung's theory, recognising the differences between a theory of personality type and a theory of personality traits. The type/trait difference in looking at personality is significant as can be seen below:

TRAIT	TYPE
Personality Traits differ only in the amount possessed by each person	Personality Types are developed through using qualitatively distinct inborn preferences
Traits are reductive The sum of an individual's traits determines all behaviour.	Type is systemic and purposeful. Behaviour expresses type. People can act in and out of type
Trait_based psychological instruments or tests: measure amounts Normally distributed scores extreme scores are important the scores show the amount of a trait possessed	Type_based psychological instruments or tests: sort into categories bi_modal or skewed scores the mid_point is important the scores show confidence in the sorting procedure
Too much or too little of a trait can be negative or diagnostic	Too much or too little of a type preference is meaningless

Using this theoretical background, the practical requirements of constructing an instrument to reflect the theory led to the following strategies:

• selection of items that enabled people to select between the functional and attitudinal opposites; and
• testing and weighting items psychometrically so that choice of items would more easily reflect individual preferences, in particular precision in the centre of the scale so that persons with indeterminate preferences would be more likely to be classified according to their true preference

One of the consequences of these issues, as well as the need to identify Dominant and auxiliary functions as prescribed by Jung's theory, was the development of a second set of Attitudes (Judging/Perceiving) not found explicitly in Jung's theory, but in Myers and Briggs view implied in his writings on the subject.

Initially, questions that became part of the MBTI^® were constructed on small 3 x 5 cards and then tested by asking anybody that walked in the door of a Myers or Briggs residence. The information from these activities, combined with the large studies engaged in by Isabel Myers (assisted by her father who utilised his connections as Director of the Bureau of National Standards) and the facilities of the Educational Testing Service from 1949, further developed these questions.

One of the interesting sidelights of this research is that Isabel Myers conducted research on these items on males and females separately. A consequence of this was the separate scoring keys for male and female for today's MBTI^® forms.

Work on the construction and development of the MBTI^® is still continuing in order to make it more effective in applying type theory, in particular the development of other forms of the MBTI^®, including translation into other languages.

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