Chapter 1
Why Personality-Intelligence Relations Matter
- Personality and intelligence are defining domains of human individuality that drive important behaviors and outcomes.
- These domains are commonly believed to be unrelated.
- However, if personality and intelligence are related, then assuming they are independent could bias research, theories, and applications.
- Some existing theories suggest there could be ties between personality and intelligence.
- We posit that:
- There are significant connections between personality and intelligence.
- There is an overarching structure and purpose to these trait constellations, shaped by environmental and evolutionary forces.
- Looking beyond the Big Five personality traits and common cognitive abilities provides important insights about the purpose and nature of differences between people.
- Our study uses modern taxonomies of personality traits and cognitive abilities to provide a higher resolution view of these domains than previous investigations.
- Our research is broad and deep. We examine major personality traits and cognitive abilities with more data than ever used before, and 93% of the personality-intelligence relations discussed here have not been previously described in detail using meta-analytic methods.
“Who are you?”
This is perhaps the most commonly asked question among humans. Despite the diverse array of answers—from names to religious beliefs, from character descriptions to life histories—a deeper question that is never asked is “Why are you?” This book builds on a century of science describing who people are to see the broader pattern in why they are.
Personality and cognitive ability are two of the most consequential sets of differences between individuals (Roberts et al., 2007). This book presents the most comprehensive examination of their relations. Cognitive abilities describe what an individual is cognitively capable of. Personality traits describe what an individual typically does. These domains encompass some of the most potent predictors of important behaviors and outcomes in educational, occupational, and personal life domains (Gottfredson, 1997; Judge et al., 1999). They influence the trajectories of individuals, including what activities they prefer (Webb et al., 2007), what environments they gravitate toward (Furnham, 1981), who they are drawn to associate with (Buss, 1985), and how well they perform their work (Dilchert, 2018; Le et al., 2007; Ones et al., 2016; Salgado et al., 2003; Schmidt & Hunter, 1998). They are also key determinants of physical, mental, and even financial health (Hatch et al., 2007; Kuncel et al., 2010). Although considerable research has separately examined the correlates and consequences of cognitive abilities and personality traits (Ones et al., 2007; Wilmot et al., 2019; Wilmot & Ones, 2019, 2022), much less is known about connections between the two domains.
In fact, cognitive abilities and personality traits are generally considered to be unrelated (e.g., Mammadov, 2022; Sackett & Ellingson, 1997). Yet, individual lives unfold as both domains of psychological differences co-manifest across environments. Springing from the confluence of genetic and environmental influences, unique constellations of personality traits, cognitive abilities, and other characteristics jointly define individuality. Our meta-analyses establish significant overlap between human cognitive abilities and personality traits by cumulating quantitative findings from the past 100 years of research.
Focusing narrowly on either cognitive abilities or personality traits hampers research, understanding, and application. If cognitive abilities and personality traits substantially covary, then studies omitting constructs from one of these domains would yield biased results, referred to as the omitted variables problem (Linn & Werts, 1971; Sackett et al., 2003). Incorrectly assuming that personality and ability are independent also results in deficient and misleading scientific theories, research studies, and behavior interventions.1 Meaningful relations between the domains would also raise the etiological question of whether some personality attributes and cognitive abilities are causally related.
Conceptual reasoning suggests that personality and cognitive ability are more closely related than commonly acknowledged. General theories linking personality traits and cognitive abilities include Cattell’s Investment Theory (1987); Ackerman and Heggestad’s Emergence of Trait Complexes Theory (1997); von Stumm and Ackerman’s Theory of Intellectual Engagement (2013); DeYoung’s Cybernetic Big Five Theory (CB5T; 2015); and Ortony, Norman, and Revelle’s Affects, Behaviors, Cognitions, and Desires (ABCD) Theory (2005). Bonds between personality and ability domains would also be consistent with other prominent individual differences frameworks (e.g., behavioral activation and behavioral inhibition [Gray, 1981, 1982], and getting along and getting ahead [Hogan & Holland, 2003]). Evolutionary theory also offers an informative frame:
(1) “evolutionary processes have sculpted not merely the body, but also the brain, the psychological mechanisms it houses, and the behavior it produces; (2) many of those mechanisms are best conceptualized as psychological adaptations designed to solve problems that historically contributed to survival and reproduction, broadly conceived; (3) psychological adaptations, along with byproducts of those adaptations, are activated in modern environments that differ in some important ways from ancestral environments; (4) critically, the notion that psychological mechanisms have adaptive functions is a necessary, not an optional, ingredient for a comprehensive psychological science.” (Buss, 2009)
We view both cognitive ability and personality as evolved psychological solutions to the difficulties and delights of life. The current research builds on previous efforts by quantifying the strength of more links than previously considered, identifying cross-domain trait constellations, and articulating an explanation of the pattern of these relations.
Previous meta-analytic examinations report personality-cognitive ability relations (Ackerman & Heggestad, 1997; Anglim et al., 2022; Schilling et al., 2021; von Stumm & Ackerman, 2013; Wolf & Ackerman, 2005). However, these efforts were limited in the scope of their investigations (e.g., focused on one factor of the Big Five or a few abilities), the sources of their data (e.g., mostly relying on published research), and the taxonomies they used to map different measures to constructs. Consequently, the findings and conclusions were also limited. Nevertheless, two main conclusions are by now well-known in the literature. First, cognitive abilities are moderately associated with a variety of openness-related traits (Ackerman & Heggestad, 1997; Anglim et al., 2022; von Stumm & Ackerman, 2013) but appear to be weakly related to other personality characteristics such as extraversion (Anglim et al., 2022; Wolf & Ackerman, 2005). Second, investment of abilities into acquired knowledge (i.e., invested abilities) requires a hungry mind (i.e., openness traits) and interest in the domain of knowledge to be acquired (Ackerman & Heggestad, 1997).
The research presented in this volume is a 24-fold expansion2 on these previous meta-analyses, enabling us to propose a more expansive theoretical framework to account for personality-ability relations. We had three goals. First, to provide a comprehensive and definitive reporting of the degree of overlap/independence between personality traits and cognitive abilities based on well-supported taxonomies of each domain. Second, to direct the attention of researchers to co-variation among previously unrecognized personality-ability pairings that may share etiology. Finally, to interpret the findings using a theoretical framework that recognizes constellations of traits and abilities that support organismal homeostasis, change, and fitness via cybernetic control. Given the pervasiveness of personality and cognitive ability and the unprecedented depth and breadth of research presented here, this book is relevant to researchers in all fields involving people, from organizational psychology to counseling to education to political science to design to epidemiology to medicine.
Our Research
People’s psychological characteristics do not come in tidy, discrete categories. Rather, individuals and their accompanying attributes are the product of evolutionary pressures that have biological and, eventually, psychological consequences. Across generations and within lifetimes, fitness in varying environments calls for adaptive strategies that result from conscious and unconscious mechanisms. Traits and abilities serve functions, and we reason that if traits and abilities serve similar functions, they will be co-related. We find empirical support for significant connections between personality and intelligence beyond openness-related personality traits, which are explained in a theoretical framework described in Chapter 6 of this book. We posit that these relations reveal an overarching structure and purpose to trait constellations, which is rooted in the evolutionary interplay between genes and environment. Finally, looking beyond the Big Five personality traits and common cognitive abilities reveals important insights about the purpose and nature of differences between individuals.
Previously, individual studies have estimated the relations between personality traits and cognitive abilities (e.g., Busato et al., 2000; Chamorro-Premuzic & Furnham, 2008; Conn & Ricke, 1994), and quantitative summaries have identified a few relations, particularly between cognitive abilities and the broad openness trait (Ackerman & Heggestad, 1997; Anglim et al., 2022; von Stumm & Ackerman, 2013). Our meta-analyses significantly build on these efforts by estimating relations of 97 cognitive abilities, 84 of which were not included in previous meta-analyses. Developments in personality models and taxonomies during the past decade and a half also afforded our research a more fine-grained, hierarchical model of the personality domain (Stanek & Ones, 2018) that extends above and below the Big Five personality factors of neuroticism, agreeableness, conscientiousness, openness, and extraversion. As a result, we were able to quantitatively estimate relations of 79 personality constructs, 28 of which were not included in previous meta-analytic investigations. Our results thus offer insights across the spectrum of personality traits and cognitive abilities (e.g., facets vs. broader factors; Cronbach, 1960; Cronbach & Gleser, 1965; Ones & Viswesvaran, 1996; Shannon & Weaver, 1949; Wittmann & Süß, 1999).
In sum, 93% of the 3,543 ability-personality relations we meta-analyzed had not been previously meta-analytically estimated. Each of these new meta-analyses contributes to basic and applied disciplines that involve personality and cognitive ability constructs and measures in their theories, research, and applications. Results reveal considerable links.
The Organization of This Book
This book is organized to communicate the thinking, approaches, findings, and implications related to our meta-analytic investigations of personality-intelligence relations. In Chapter 2, we provide a brief overview of the personality and cognitive ability domains. Chapter 3 summarizes our meta-analytic methodology, with more comprehensive details provided in Appendix E. Chapters 4 and 5 present the results of our meta-analyses from the perspective of cognitive ability and personality, respectively. Chapter 6 lays out a theory of individual differences that accounts for our meta-analytic results, Chapter 7 presents the results of our meta-analyses in the light of our theory, and Chapter 8 discusses trends that cut across the results. Chapter 9 notes the boundaries of our current understanding of personality-ability relations as well as opportunities for future exploration. Chapter 10 concludes the book by discussing the meaning and implications of our findings. Appendices A and C provide definitions of all the cognitive ability and personality constructs we refer to throughout the book, while Appendices B and D provide information about which measures we used as indicators of each construct.
Only a pair of fools would try to distill 100 years of research on two of the broadest topics in psychology and thousands of meta-analyses into 225 pages of unorthodox conclusions. We proceed.
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