Personality Assessment in Groups of Different Verbal Intelligence Levels

The differentiation of personality by intelligence hypothesis, which has mixed support in the literature, predicts that personality is more variable for more intelligent individuals. This study aimed to test that hypothesis by comparing variances, reliability coefficients, and inter-scale correlations of personality as assessed by self-reports between groups of participants with different intelligence scores. We used two independent datasets (N₁ = 655; N₂ = 836; N_total = 1491) in which the same vocabulary test was used as a measure of verbal intelligence, but personality was measured as self-report by different inventories (NEO-FFI and HEXACO-100). As the verbal ability scores had a normal distribution, the combined mean was calculated, and empirical groups were generated within each sample to compare groups of participants who indicated a low-ability group (G1) and the high-ability group (G3). Results mostly support the differentiation hypothesis in the NEO-FFI dataset, where participants in G3 have higher variances and reliability coefficients than participants in G1, but do not show lower inter-scale correlation coefficients. However, the same trend was not found in the second sample where personality was assessed by the HEXACO inventory. In conclusion, the results of this study provide only partial support for the personality differentiation by intelligence hypothesis.