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KeywordsPersonality Trait Intelligence Test Fluid Intelligence Learning Achievement High Intelligence
Intelligence-personality associations refer to theoretical and empirical relationships that exist between intelligence, which is the ability to learn and adapt, and personality traits which describe characteristic patterns to feel, think, and behave.
Intelligence and personality are the two psychological characteristics or construct dimensions that account for the majority of differences that occur between people in behavior, development, and life outcomes. Intelligence, defined as the ability to learn and adapt, describes individual differences in maximum performance or what a person can do. Accordingly when measuring intelligence, test takers are instructed to do their best to identify the correct response to a question or the right solution for a task. By contrast, personality refers to the variance in those behavioral tendencies that predict what a person will typically do. Thus, personality tests ask for candid and truthful responses about typical behaviors and negate the idea of correct or “best” answers. Both intelligence and personality – markers of maximum and typical performance, respectively – predict a wide range of life outcomes, including educational and professional achievement, well-being, health, and longevity. To elucidate the antithesis of sharing the power to predict and explain behavior while differing in their conceptual frameworks, three perspectives have emerged on intelligence-personality associations. The first and oldest perspective views intelligence and personality as independent domains. The second proposes an association at the level of observation, whereby personality is thought to affect how a person performs in an intelligence test and vice versa. The third perspective assumes a conceptual relationship between intelligence and personality, whereby one domain informs the development and nature of the other. Each perspective has uniquely influenced the study of individual differences and the psychological literature at large.
Perspective of Independence
At the beginning of the twentieth century, the earliest individual differences researchers considered intelligence and personality to be independent domains. Accordingly, intelligence and personality were treated as separate entities that shared no meaningful relationship, although it was recognized that both added to one another in the prediction and explanation of individual differences in behavior (Spearman 1904; Webb 1915). The notion of independence emerged initially from the fact that intelligence and personality define different performance elements (i.e., maximum versus typical performance; see above). In addition, it was believed that both domains were relevant for different life outcomes; that is, intelligence and personality were thought to diverge in their predictive validity. Specifically, intelligence scores were predominantly applied to forecast a person’s achievement potential in terms of school performance and professional attainment. By contrast, personality was mainly thought of in the context of intraindividual outcomes, such as subjective well-being or life satisfaction, and interpersonal factors, including the quality and quantity of all kinds of social relationships (Vernon 1933).
Factor analytic studies further substantiated the theoretical division between intelligence and personality, because they extracted orthogonal factors that differentiated ability-related variances from nonability variances (Webb 1915). With that, the theoretical independence of intelligence and personality became an empirical reality. The enforced orthogonality of intelligence and personality dictated the outcome of all subsequent studies on intelligence-personality associations, because infinitesimal correlations between intelligence and personality scale scores are the inevitable consequence of statistically separating ability from nonability variance (e.g., Major et al. 2014).
Throughout the twentieth century, the perspective that intelligence and personality were independent entities governed psychology and individual differences research. It caused a permanent rift, with individual differences researchers identifying either as personality or as intelligence researchers and both “camps” publishing their findings in different journals, attending different scientific meetings, and pursuing different research agendas. However, today the similarities between intelligence and personality have been widely recognized to outweigh their alleged differences. Both can be reliably quantified through standardized psychometric tests, both are genetically influenced, both show considerable temporal stability across the lifespan, and both predict all relevant life outcomes, ranging from occupational performance to longevity. Accordingly, recent years have witnessed an increase in crossover research that brings together intelligence and personality in new ways, finally abandoning the perspective of independence. As a result, we are now at the beginning of a unified research paradigm for individual differences research that recognizes the importance of studying intelligence-personality associations.
Associations at the Measurement Level
An alternative to treating intelligence and personality as independent domains is the perspective that one construct dimension might affect the assessment of the other and vice versa. Thus, people’s differences in intelligence may inform how they complete a personality questionnaire, and conversely, a person’s personality traits are thought to influence how they perform in an intelligence test. This perspective implies an association of intelligence and personality at the level of observation rather than a substantive relationship between both constructs.
Intelligence → Personality Assessment
Higher intelligence is thought to enable a better understanding of personality test items, and thus, it should result in more “accurate” or truthful responses. Accordingly, the personality scores of more intelligent people are hypothesized to be more dispersed than the scores of less intelligent individuals, who have a poorer comprehension of the specificity of a given personality test item and thus, provide comparatively undifferentiated response. In this context, it has been suggested that the link between intelligence and personality differentiation may also constitute a developmental phenomenon, rather than merely existing at the measurement level (Austin et al. 2000). The developmental viewpoint proposes that higher intelligence enables individuals to access over time a greater variety of situations and make more diverse experiences, which in turn create more differentiated personality profiles than those of people with lesser mental ability.
The empirical evidence for differentiation of personality by intelligence is limited and has yet to produce conclusive results (von Stumm et al. 2009). In other words, it has not been reliably demonstrated that higher intelligence is indeed associated with a significant advantage in comprehending personality test items and that then informs greater personality differentiation at the measurement level. Likewise, intelligence has not been shown to predict engaging in a greater range of activities or situations, whose experiences would then potentially lead to developing a differentiated personality. That said, intelligence has been consistently found to lead to better performance and achievement outcomes across situations, but this does not imply a positive relationship between intelligence and the scope or extent of activity engagement. Thus, intelligence-personality associations at the measurement level, where intelligence influences the assessment of personality, are currently not supported by empirical evidence.
Personality → Intelligence Test Performance
Although personality may influence how people complete intelligence tests in many different ways, the majority of studies on this phenomenon have focused on two traits in particular, namely, extraversion or neuroticism.
Extraversion, which manifests in outgoing, talkative, energetic behaviors (“Extraversion”), spans impulsivity and boredom avoidance that inform test-taking styles in two ways. For one, extraversion may lead to a trade-off between speed and accuracy, so that people, who score high on extraversion, accept an increased error rate in favor of working quickly through a test, while those low on extraversion (i.e., introversion) display the opposite pattern and emphasize accuracy over time. Overall, however, different test-taking styles have a zero net effect on the total score of an intelligence test (Bates and Rock 2004). Accordingly, the theory that extraversion was systematically associated with a speed-accuracy trade-off in intelligence test performance has not been empirically substantiated (von Stumm et al. 2011a). For the other, extraversion interacts with the situational factors or conditions under which an intelligence test is administered. Several studies have shown that people who score high on extraversion perform better when the intelligence test is administered in a stimulating or even slightly stressful settings, for example, when the test is timed or background noise can be heard (Revelle et al. 1976; Bates and Rock 2004). By comparison, people scoring high on introversion perform increasingly worse as the conditions of test administration increase in stress and stimulation, presumably because introverts prefer quiet environments to achieve optimum performance levels (Revelle et al. 1976). While several studies support that the interaction between extraversion/introversion and administration conditions affects intelligence test performance, their corresponding effect sizes range from small to moderate. To summarize, the effects of extraversion on intelligence test performance appear to mainly occur because of an interaction with test administration conditions but less so because of a relationship with test-taking styles. Regarding the magnitude of this association, the influence of extraversion on how people complete an intelligence test is overall modest.
The personality trait neuroticism is characterized by anxiety, worry, and negative affect (“Neuroticism” entry). Across studies, including several large-scale meta-analyses, neuroticism and the related trait dimension of test anxiety have been shown to be negatively associated with intelligence test performance with effect sizes ranging from small to moderate (Hembree 1988; Wicherts and Scholten 2010). Furthermore, studies that employed clinical samples and mood induction paradigms, for example, using sad music or images to induce low mood, have shown that negative affect impairs short- and long-term cognitive performance, especially when negative mood states are either extreme or enduring or both (Joormann 2008).
Two alternative rationalizations exist that explain the negative relationship between neuroticism or more generally negative emotional experiences and intelligence test performance. The first proposes that anxiety-related traits lead to task-irrelevant information processing, which demands cognitive resources that are then no longer available for performing in the intelligence test (cf. dual-task processing; Ellis and Ashbrook 1988). The other rationalization posits that people who are highly anxious may be inherently less intelligent, and thus, the negative association between ability and anxiety may persist at the construct level. However, no plausible theory has been proposed that justifies why anxiety and low ability should co-occur. With that said, to date, conclusive evidence is not available to support the idea of task-irrelevant processing above the one of an inherent relationship between intelligence and anxiety-related traits.
In summary, the empirical evidence for intelligence-personality associations at the measurement level is generally sparse, but two phenomena are thought to be relatively robust. For one, extraversion/introversion interacts with test administration conditions in the effect on intelligence test performance, with extraverts performing better under more stimulating or stressful testing conditions but introverts performing worse. For the other, intelligence test performance appears to be impaired by anxiety and negative emotionality, with people who score high on these and related trait dimensions doing less well in cognitive ability tests.
Associations at the Conceptual Level
An association between intelligence and personality at the conceptual level assumes a developmental relationship, whereby personality traits influence the development of intelligence across the lifespan. Thus, the developmental relationship is thought to be unidirectional (i.e., personality on intelligence) rather than reciprocal (i.e., personality on intelligence and vice versa).
Theories of adult intelligence (“Intelligence/Adult Intelligence” entry) typically differentiate the capacity for knowledge or fluid intelligence or biological reasoning power from the knowledge possessed or crystallized intelligence or learned knowledge and experience (Ackerman 1996; Hemnon 1921). The capacity for knowledge refers to intelligence as the ability to learn and adapt, which is commonly assessed by maximum performance intelligence tests, whose scores are fairly independent of personality (cf. independence perspective above). The capacity for knowledge transforms into actual knowledge over time, as it becomes invested in learning opportunities and experiences. The investment of the capacity for knowledge is guided by so-called investment personality traits that determine when, where, and how people invest and apply their intelligence to learn. In this model, the investment of intelligence is understood as typical behavior that leads to the accumulation of knowledge (Ackerman 1996). Thus, we might want to think of investment traits as the bridging construct that connects intelligence and personality within a developmental process.
Investment Personality Traits
Investment personality traits refer to the tendency to engage in and seek out cognitive activities that are novel, intellectually stimulating, and effortful, for example, reading a challenging book or attending an evening class to study an unfamiliar subject (von Stumm and Ackerman 2013). Given these examples, it is important to note that a specific set of precise “investment behaviors” has not been identified or proposed by previous research.
A recent review revealed that more than 30 investment personality trait scales exist in the psychological literature that were independently conceived by different researchers but refer unanimously to individual differences in the tendency to invest in learning and accumulate knowledge (von Stumm and Ackerman 2013). Two principal trait dimensions are differentiated within the investment trait construct space. On one hand, a cluster of trait variables refers to the “hunger for knowledge,” which is also known as epistemic or intellectual curiosity. This cluster is best characterized by the tendency to seek out traditional learning opportunities and to pursue effortful cognitive engagements; hence, it is predictive of formal learning achievements, for example, in school or university (von Stumm et al., 2011b). On the other hand, a cluster of open exploration tendencies has surfaced that is comparatively less intellectual but concentrates on producing novel sensory and perceptual experiences. This dimension of openness is less predictive of traditional learning achievements (Poropat 2009) but may be more conducive to learning that occurs in everyday life situations, outside formal education settings. Support for the division of the investment trait construct space into “intellectual” and “non-intellectual” dimensions came first from psychometric studies that observed distinct personality factors of intellect and openness. Later brain imagining studies and behavioral genetic research designs further substantiated that investment is best thought of in terms of two distinct trait dimensions (e.g., DeYoung et al. 2009; Wainwright et al. 2008). While the duality of investment traits is widely acknowledged today, researchers have yet to agree on a unanimous terminology to refer to both dimensions.
Investment and Intelligence
Evidence for the effects of investment personality traits on intellectual development comes predominantly from cross-sectional studies, even though prospective research designs are better suited to study the investment theory. A recent meta-analysis of cross-sectional studies showed that various investment personality traits are positively and moderately correlated with makers of adult intelligence, for example, academic achievement and knowledge test scores (von Stumm and Ackerman 2013). Although this association tends to reduce after adjusting for intelligence (i.e., capacity for knowledge) and other personality traits that contribute to learning achievement (e.g., grit, conscientiousness (“Grit/Conscientiousness” entry)), the association between investment traits and academic achievement remains significant in well-powered studies (von Stumm et al. 2011b).
Only one longitudinal study has been reported to date that tested the long-term effects of investment personality traits on intelligence in young adults. Data came from a sample of 239 Bavarian adolescents, who were assessed on investment and different kinds of intelligence at age 17 and 23 years (Ziegler et al. 2012). Investment personality traits at age 17 were found to be positively associated with gains in the capacity for knowledge (i.e., fluid intelligence) between the ages of 17 and 23 years. In turn, the gains in the capacity for knowledge were related to greater knowledge and growth in crystallized intelligence over the same time period. These findings provide partial support for the investment hypothesis, but they also highlight that the effect of investment personality traits on accumulating knowledge may be indirect and mediated by fluid intelligence. However, it is too early to draw firm conclusions here, because the existing evidence base is limited and replication studies are not yet available.
Several other longitudinal studies sought to substantiate the investment theory, albeit in ageing samples that were on average very old (i.e., age 70 years and more). Because ageing populations differ categorically in their cognitive structure, development, and needs from children and adolescents, the investment theory was found to be badly suited to explain individual differences in cognitive decline (von Stumm and Deary 2012). This is neither a surprise nor a problem for the validity of investment traits, because the investment theory was conceived to explain why some people learn better and accumulate more knowledge than others, not why some preserve their cognitive function for longer than others across old age.
Intelligence and personality capture the majority of the psychological differences and similarities that occur between people. Intelligence indicates maximum performance, while personality marks typical performance. As a consequence of this antithetic conceptualization, the study of ability (i.e., intelligence) was traditionally separated from the study of nonability variance (i.e., personality). However, the recent psychological literature has overcome this disconnect and explored ways in which intelligence and personality are related to one another. The most promising avenue of research in this context suggests that personality traits influence the development of intelligence across the lifespan. Accordingly, robust associations have been reported between learning achievement and so-called investment traits that determine when, where, and how people invest their intelligence and thus, the domains in which they accumulate knowledge. However, the current empirical evidence for the investment theory is of limited validity, because most of it comes from cross-sectional studies. To truly advance our understanding of intelligence-personality associations, longitudinal studies are needed that assess both intelligence and investment, as well as other personality traits, repeatedly across assessment occasions. Such studies will be pivotal in producing reliable knowledge about the role that intelligence-personality associations play for individual differences in development.
- Ellis, H. C., & Ashbrook, P. W. (1988). Resource allocation model of the effects of depressed mood states on memory. In K. Fiedler & J. Forgas (Eds.), Affect, cognition, and social behavior (pp. 35–42). Göttingen: Hogrefe.Google Scholar
- Joormann, J. (2008). Cognitive aspects of depression. In I. H. Gotlib & C. Hammen (Eds.), Handbook of depression (pp. 298–321). New York: Guilford Press.Google Scholar
- von Stumm, S., Chamorro-Premuzic, T., & Ackerman, P. L. (2011a). Re-visiting intelligence-personality associations: Vindicating intellectual investment. In T. Chamorro-Premuzic, S. von Stumm, & A. Furnham (Eds.), Handbook of individual differences. Chichester: Wiley-Blackwell.Google Scholar
- von Stumm, S., Hell, B., & Chamorro-Premuzic, T. (2011b). The hungry mind: Intellectual curiosity as third pillar of academic performance. Perspectives on Psychological Science, 51, 12–31.Google Scholar
- Webb, E. (1915). Character and intelligence. Unpublished Doctoral Dissertation, University of London.Google Scholar