In a two-sample investigation of 766 adolescents, we examined the associations and incremental validity of test-based intelligence, parent-rated conscientiousness, and self-rated achievement striving motivation with objective (grades) and subjective (parent-reported and self-reported academic performance) measures of academic achievement. The two studies yielded largely similar results. Intelligence was related to objective and subjective performance ratings. Conscientiousness showed associations and explained variance beyond intelligence in grades and parent-reported but mostly not in self-reported academic performance. Achievement striving motivation was largely related to and explained variance beyond intelligence and conscientiousness in grades and subjective performance ratings. Findings indicate that traits and motives predict objective and subjective academic achievement measures incrementally to abilities. Differential relationships for conscientiousness depended on the informant of academic performance.
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