The reliability of the Thematic Apperception Test

Controversy over the TAT's reliability may stem largely from the mis-application of traditional psychometric measures, which are inappropriate to this test. The TAT is implicitly based on a multiple regression model, for which coefficient alpha is not appropriate. Also, test-retest correlations may be adversely affected by the standard instructions to write a "creative" story. In a test-retest study, 47 high school students retook the TAT after a year with instructions designed to break the implicit set to produce a new and different story from that previously written. The test-retest correlations were r = .48 (need for affiliation) and .56 (need for intimacy), or approximately the same as those for, e.g., the MMPI, 16PF, and CPI, It was demonstrated that this high stability over time was not due to subjects' recalling and repeating previous responses. Finally, it was shown that alpha considerably underestimated the test-retest reliability, contrary to assumptions of classical psychometrics.