Intelligence and variability in personality

Using archival data, this study tests the Differentiation of Personality by Intelligence (DPI) Hypothesis based on responses from 794 mature students with an average age of 29.74 years ( SD = 2.67). Individuals completed three intelligence measures and an omnibus personality scale measuring 16 personality traits. For each intelligence measure, the sample was split into tertiles and the variability of each of the personality trait scales were compared between the higher versus lower intelligence scoring thirds. Based on variance ratio tests, 29 of the 48 comparisons (60 %) suggested some support for the DPI Hypothesis, although most of the comparison tests (79 %) were statistically non-significant. The results were compared to a previous study examining the DPI Hypothesis with the same personality scale, and in general, the results failed to replicate, with only seven of the 16 findings replicating. As the DPI Hypothesis is typically supported with other personality measures, and not supported across all measures, we suggest that there may be an influence from the personality scale item content and provide a suggestion of how to test this possible influence.