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Cognitive ability, personality and interests are three distinct topics of investigation for psychology. In the past two decades, however, there have been growing appeals for research and theories that address the overlap among these domains (Ackerman & Heggestad, 1997; Armstrong, Day, McVay, & Rounds, 2008). One example of such a theory is PPIK theory (intelligence-as-process, personality, interests, and intelligence-as-knowledge) by Ackerman (1996). Integrative theories have the potential of not only increasing our theoretical understanding of the development of these individual differences, but of and improving vocational guidance through better prediction of future occupation (Armstrong, Su, & Rounds, 2011; Johnson & Bouchard, 2009). The research of this thesis was centered on examining the links among cognitive ability, personality and interests. The data came from Project TALENT (PT), a nationally-representative sample of approximately 400,000 American high school students from 1960 (Flanagan et al., 1962). A secondary topic was whether an integrated view could improve the prediction of attained occupation. This was tested with occupational data from follow-up PT surveys, conducted 11 years after high school. The first study addressed the structure of the PT intelligence tests. Three popular models of intelligence were compared through factor analysis: the Extended Fluid-Crystallized (Gf-Gc), Cattell-Horn-Carroll (CHC) and Verbal- Perceptual-Image Rotation (VPR) models. The VPR model provided the best fit to the data. The second study was an investigation of linear and nonlinear intelligence-personality associations in Project TALENT. The ten PT personality scales were related to the Big Five personality factors through content examination, consistent with previous research (Reeve, Meyer, & Bonaccio, 2006). Through literature review of studies on intelligence and the Big Five, 17 hypotheses were made about linear associations and quadratic associations of personality traits with general intelligence (g). The majority of the hypotheses were supported in all four grade samples: 53% in male samples, and 58% in female samples. The most notable finding, contrary to previous research, was that quadratic associations explained substantive variance above and beyond linear effects for Sociability, Maturity, Vigor and Leadership in males, and Sociability, Maturity and Tidiness in females. The third study examined associations between cognitive ability and interests, and their capacity to predict occupational type. Specifically, Ackerman’s PPIK theory suggests that there are two “trait complexes” that are combinations of cognitive abilities and interests (termed science/math and intellectual/cultural). Trait complexes were derived from PT data separately by latent class analysis and factor analysis. It was hypothesized that they should have validity equal to or greater than individual intelligence and interests scores in predicting attained occupation. Instead, trait complexes derived through latent class analysis predicted substantially less variance in occupation than individual scales. The factor-analytic trait complexes performed more like the scales, but one trait complex (which involved g centrally) was inconsistent with PPIK theory. Overall, the trait complexes of PPIK theory were not supported. The results of the three studies are discussed in the context of existing integrative theories, and suggestions for future research are provided.