The Irrational Ape: Why Flawed Logic Puts us all at Risk and How Critical Thinking Can Save the World

by David Robert Grimes

Perhaps the most pervasive example is the Myers–Briggs Type Indicator (MBTI) test beloved by many institutions. This purports to measure psychological styles in how people make decisions and is used to measure aptitude for jobs, personal training and even marriage counselling. But despite the enthusiasm with which MBTI has long been deployed, studies to date indicate that it has very poor validity and fails to measure what it claims to. Were this not enough, it has low reproducibility, and the same subject can yield radically different personality results even a few days apart. Much of the criticism of these tests has focused on the vague nature of the testing questions, which lend themselves to the Forer bias of assigning a high rating to positive descriptions. The defects of this test prompted psychometric specialist Robert Hogan to opine that ‘most personality psychologists regard the MBTI as little more than an elaborate Chinese fortune cookie’.