Does conscientiousness predict college GPA better for high ability groups?

Despite a well-established literature on the predictive validity of conscientiousness and intelligence for academic achievements, few studies have examined non-linear effects of these constructs in predicting academic outcomes. In the current study, conscientiousness, intelligence, and a conscientiousness by intelligence interaction predicted high school and college GPAs. Tests and surveys were administered or retrieved from university records for 200 undergraduate students. Based on Spearman's Law of Diminishing Returns (SLODR), conscientiousness was expected to predict academic outcomes better for high ability individuals, due to the diminishing predictive power of intelligence and increasing influence of non-intelligence factors. Consistent with previous research, main effects for intelligence and conscientiousness were observed. However, contrary to SLODR and prior findings, support was not found for a conscientiousness by intelligence interaction in predicting academic outcomes. Limitations and implications are discussed.