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
