Schmidt (2014, PS) - A General Theoretical Integrative Model of Individual Differences.pdf

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Perspectives on Psychological Science2014, Vol. 9(2) 211218 The Author(s) 2014Reprints and permissions:sagepub.com/journalsPermissions.navDOI: 10.1177/1745691613518074

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This article attempts to integrate the substantive and the-oretical questions addressed in four recent articles (Nye,Sue, Rounds & Drasgow, 2012; Schmidt, 2011; Valla &Ceci, 2011; and von Stumm, Hell, & Chamorro-Premuzic,2011) that appeared in Perspectives on PsychologicalScience. These four articles all focus on the effects ofinterests, in conjunction with abilities, on academic and/or occupational achievement. The goal is to place thefindings of these articles in the context of an overall theo-retical model or theory that incorporates the findings ofthese articles and related findings from the literature and

also clarifies the origins and effects of sex differences ininterests. The interests examined range from very general(e.g., general intellectual curiosity) to those specific toparticular occupational groups (e.g., scientific, technical,engineering, and math; STEM occupations). At the inter-mediate level of specificity, the most widely acceptedmodel for occupational interests is Hollands (1985, 1996)model of six basic interest types: Realistic (e.g., police offi-cer or carpenter), Investigative (e.g., scientist, researcher),Artistic (e.g., poet, actor), Social (e.g., social worker, ele-mentary school teacher), Enterprising (e.g., business

founder, entrepreneur), and Conventional (e.g., book-keeper, administrative assistant). The level of specificityof interests studied varies across the articles. The focus ofthe von Stumm et al. article is on the broadest possibleinterest (general interest in knowledge acquisition),whereas the Nye et al. article examines all six of theHolland interest types. The Valla and Ceci and Schmidtarticles fall in between these two in the level of specificityof the interests they focus on. In terms of the Hollandinterest model, the Valla and Ceci article focuses onInvestigative interests and the Schmidt article focuses on

Realistic interests. These two articles, unlike the othertwo, focus on sex differences in occupational interests.

To set the stage for this integrative effort, I first sum-marize each of these articles, starting with the two studiesthat examine sex differences in occupational interests.

8074PPSXXX10.1177/1745691613518074SchmidtACommentary onFourRecentArticles

Corresponding Author:

Frank L. Schmidt, Tippie College of Business, University of Iowa, Iowa

City, IA. 52242

E-mail: [email protected]

A General Theoretical Integrative Modelof Individual Differences in Interests,

Abilities, Personality Traits, and Academicand Occupational Achievement: ACommentary on Four Recent Articles

Frank L. SchmidtTippie College of Business, University of Iowa

AbstractThis commentary integrates the contents of four recent articles on individual differences (Nye, Su, Rounds, & Drasgow,2012; Schmidt, 2011; Valla & Ceci, 2011; von Stumm, Hell, & Chamorro-Premuzic, 2011) in a causal theoretical model.In this model, introversion and fluid intelligence cause interest in general learning (intellectual curiosity), which in turnis a major cause of crystallized intelligence. Certain specific interests and fluid intelligence also contribute to crystallizedintelligence. Prenatal testosterone hormone conditioning is postulated to cause sex differences in certain specificinterests but not in others. Crystallized intelligence, specific interests, and the personality trait of conscientiousnesscause adult academic and occupational performance, whereas crystallized intelligence is the main cause of goodmental functioning at older ages. Research is presented supporting each link in the model.

Keywords

individual differences, interests, abilities, personality, academic achievement, occupational achievement

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212 Schmidt

Valla and Ceci (2011): Sex Differencesin STEM Interests and Abilities

Valla and Ceci critiqued the evidence in the literaturesupporting brain organization theory. This theory holdsthat developmental events during gestation (i.e., malefetal exposure to testosterone) create sex differences in

brain lateralization that in turn produce sex differences intwo abilities (mathematical ability and spatial ability)hypothesized to be critical for performance in STEMareas. Valla and Ceci reviewed the evidence on sex differ-ences in these abilities and found that the literature doesnot support a sex difference in mean level of math ability.However, the male distribution is more variable, causingthe individuals at the upper tail of the distribution to bedisproportionally male. (This is also true of the lower tailof the distribution.) In the case of spatial abilities, Vallaand Ceci found that the literature indicates a substantialmale superiority in three-dimensional visualization but

not in two-dimensional spatial visualization. In the caseof memory for spatial location of objects in the environ-ment, females are superior. Interestingly, they presentedno evidence that any of these forms of spatial ability con-tribute to success in STEM areas over and above theeffects of general mental ability (GMA; intelligence) orother abilities. I have also never been able to locate suchevidence. So the evidence supporting the sex differencesin abilities predicted by brain organization theory ismixed. This conclusion is consistent with those of Fine(2010a, 2010b).

Valla and Ceci stated that some studies indicate thatprenatal testosterone exposure may affect interests and

preferences much more than it affects abilities:

In this scenario, androgenization of the brain mighttilt early preferred play toward spatial activities(e.g., block-building and gross motor play) whichmight foster later spatial and numerical achieve-ment, as some sex difference research indicates(Ceci, Williams, & Barnett, 2009). (Valla & Ceci,2011, p. 139)

They explored this idea in more detail later in thearticle (pp. 140141), presented evidence for its plausibil-

ity, and stated that this evidence suggests that the influ-ence of sex differences due to prenatal testosteroneexposure is not directly on ability, but emerges as a func-tion of interest (p. 141).

This hypothesis is developed more fully in Ceci et al.(2009). It may be that the main effect of prenatal hor-mones is on sex differences in interests and not on abili-ties. A much larger percentage of males are interested ininanimate things (i.e., physical phenomena) rather thanpeople or other living things, and a much larger

percentage of females are interested in people and otherliving beings rather than inanimate things. As shown in amajor meta-analysis, this difference is quite largealmost1 standard deviation (d= .93; Su, Rounds, & Armstrong,2009). This research is summarized in more detail in theSchmidt article. This difference in interests is much largerthan the largest sex difference in the ability domain: thedifference on three-dimensional spatial rotation ability,which ranges in various meta-analyses from .50 to .80standard deviations (Valla & Ceci, 2011).

Schmidt (2011): Sex Differences inTechnical Aptitude

The Schmidt article focuses on the development of sexdifferences in technical aptitude (as measured by tests ofmechanical and electrical aptitude). Technical aptitude isviewed as one of many possible indicator variables forGMA, along with verbal, quantitative, and other aptitude

measures. There is considerable evidence that in groupsin which there is no sex difference on other GMA indica-tor variables, there is a substantial sex difference favoringmales on measures of technical aptitude. This findingleads to the hypothesis that technical aptitude measures,used as GMA indicators, might lead to underestimation offemale GMA. This would be important because researchevidence shows that it is GMA that predicts job perfor-mance and that, after properly controlling for GMA, thespecific indicators of GMA make no additional contribu-tion to job performance prediction. GMA as defined hereis identical to general crystallized intelligence as definedin Cattells (1971, 1987) theory of intelligence (discussed

in the Fluid and crystallized intelligence section).This article cites convincing research evidence showingthere is no overall sex difference in GMA, a finding thatwas also confirmed in the data set used in that article.Based on a very large sample, this study found that tech-nical aptitude does underpredict female GMA, as hypoth-esized. Another way of stating this finding is this:Technical aptitude tests used as indicator measures ofGMA overstate the relative general intelligence level ofmales and understate that of females.

The Schmidt article presents a theory explaining the sexdifference in technical aptitude. This theory postulates that

the ultimate cause of lower average female technical apti-tude scores is not any initial aptitude or ability differencebut rather a lifelong lower average female level of interestin technical areas. In this theory, technical interests lead totechnical experiences (e.g., hobbies focusing on electricaland mechanical pursuits and activities), which in turncause increased technical knowledge and results in higherlevels of technical aptitude. This process produces theobserved sex differences because the proportion of indi-viduals with initial technical interests is larger among males

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A Commentary on Four Recent Articles 213

than among females. The Schmidt article does not postu-late a neurological, gestational, or hormonal basis for thissex difference in interests, as Valla and Ceci did, but it doesreview the research evidence showing that it is difficult, ifnot impossible, to change interests. The intuitive feeling ofmany people is that interests are much easier to modifythan abilities, but the research evidence does not supportthis intuition.

The similarity between the theory presented in Schmidtand those presented in Valla and Ceci and Ceci et al.(2009) is apparent. Each suggest that interests play animportant causal role in the development of knowledge,skills, and aptitudes. This will be reflected in the integra-tive theory presented later.

Von Stumm et al. (2011): GeneralIntellectual Curiosity

Both Valla and Ceci and Schmidt focused on the effects

of specific or narrow interests on outcome areas that arealso specific or narrow. The focus in Valla and Cecis arti-cle is on the impact of interests on the development ofabilities or aptitudes believed to be important for successin STEM fields. The Schmidt article focuses on the effectof technical interests on the development of technicalknowledge and technical aptitude. The technical occupa-tions (such as machinist, mechanical repairman, electri-cian, computer trouble shooter, etc.) can be viewed aslower level versions of the STEM occupations. They canalso be viewed within the Holland interest model asRealistic occupationsa category that is adjacent to, andpositively correlated with, Investigative occupations, thecategory to which STEM occupations fall. In either case,there is a similarity between STEM interests and technicalinterests. The Von Stumm et al. article is very differentfrom these two articles: It focuses on what is probablythe most general of all interests, the general interest inlearning or knowledge acquisition. The term they use forthis interest is intellectual curiosity (also sometimesreferred to as need for cognition), but it can also beviewed as a broad interest in general learningthe pro-clivity to seek knowledge in a wide variety of knowledgeareas. The correlation between measures of interest ingeneral knowledge acquisition such as Ackermans

Typical Intellectual Engagement (TIE) scale (Ackerman,1999; Goff & Ackerman, 1992) and GMA suggests thatintelligence is one cause of TIE, but substantial variationremains after controlling for GMA, no matter how it ismeasured. So even among people with the same level ofGMA, there are wide variations in the level of this broad-est of interests. As noted by von Stumm et al., the TIEscale is the most widely used measure of this trait, andsubsequently I use TIE as the label for this interest.

Should TIE be viewed as a personality trait or asthe broadest of all possible interests? This distinctionis not an easy one and is of necessity somewhat arbitrary.Personality in its broadest sense includes all traitsinterests, traditional personality traits, abilities, values,etc. All of these determine behavioral proclivities or pro-pensities. For example, the personality trait of Conscien-tiousness causes a proclivity toward ordered planning,organization, persistence, and achievement. Likewise thetrait of Extroversion causes a propensity toward gregari-ousness and social interaction in general. The categoriza-tion of TIE as an interest rather than a personality traitstems from the concept of a continuum of specificity ofinterests ranging from the most narrow and specific tothe most general. For example, if we start from a verynarrow interest in, say, knowledge of the biology of mon-arch butterflies, it is apparent that successive expansionsare possible in the direction of greater generality: knowl-edge of the biology of all insects, knowledge of the biol-

ogy of insects and all other animals, knowledge of thebiology of all animals and plants, knowledge of the biol-ogy of all life forms, knowledge of nonliving things, andultimately, all forms of knowledge. As one moves alongthis continuum of interests, one eventually arrives at themost general point, which is interest in acquisition ofknowledge about almost everything. At each point onthe continuum, there is much variability among individu-als, ranging from extreme interest to no interest at all.This is just as true at the point of the broadest interest asit is at the preceding, less general points.

The von Stumm et al. article reviews the literature onTIE and the literature showing the effects of the traits ofConscientiousness and GMA on academic performance.The main focus of the von Stumm et al. article is on therelative causal impacts of GMA, Conscientiousness, andTIE on academic performance. Based on data compiledfrom meta-analyses in the literature and from their ownmeta-analysis of the relation between TIE and academicperformance, they test multiple path analysis models(after correcting for biases caused by measurement error).The model that is found to provide the best fit to the dataand to plausible theoretical assumptions is one in whichGMA, Conscientiousness, and TIE are all direct causes ofacademic performance. The relative strengths (standard-

ized path coefficients) are .35 for GMA, .20 forConscientiousness, and .20 for TIE. This finding showsthat the broad interest in general knowledge acquisitionexerts a causal effect on general academic performanceeven after controlling for general intelligence and thepersonality trait of Conscientiousness (the only personal-ity trait found to correlate with academic performance).

What makes their findings important is the broad andgeneral nature of the dependent variable of academic



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214 Schmidt

performance. This is not limited to particular subjects orcourses; it encompasses performance across all academicsubjects and courses. What this finding shows is that thebroadest of all possible interests has a causal impact onthe broadest of all measures of academic performance orlearning. This appears to be a strong test of the real worldrelevance of a very broad interest measure.

The Nye, Su, Rounds, and Drasgow(2012) Article: Holland Interestsand Academic and OccupationalAchievement

Like Valla and Ceci and Schmidt, the Nye et al. articlefocuses on the impact of specific occupational interest cat-egories, namely the six interest areas in the Holland model(discussed earlier). The ultimate conclusion from theirmeta-analysis is that interest in specific occupation typespredicts job performance and tenure in those occupationsand predicts academic performance and persistence inareas of study related to those occupations. Further, theyshow that an index of congruence (similarity) betweenpeoples strongest interests and the extent to which theiracademic or work environment reflects and supports theseinterests predicts academic and work performance andpersistence better than do the simple interest scale scores.The correlations for the congruence measures are mostlyin the .20 to .35 range, whereas the correlations for indi-vidual interest scale scores (without reference to congru-ence) are lower, ranging from about .05 to .15. (Theauthors correct all correlations for biases created by mea-

surement error and range restriction.) Individuals attemptto find and enter college majors, occupations, and specific

jobs that are most consistent with their strongest interests(as measured intraindividually, i.e., ipsatively). The Nyeet al. article is methodologically and conceptually complexand is a challenge to read. However, it is possible to sum-marize its main findings in a straightforward manner, asdone here.

The Nye et al. article focuses on both academic andoccupational performance, whereas the von Stumm et al.article focuses only on academic performance. The vonStumm et al. article shows that the broad interest in acqui-sition of general knowledge predicts general academicperformance (i.e., learning), even after controlling forintelligence and the personality trait of Conscientiousness.The Nye et al. study shows that interests in six specificoccupational areas predict (although weakly) both aca-demic and occupational performance in those areas andthat this prediction is stronger when the academic or jobenvironment is consistent with the individuals strongestinterest.

A Proposed Integrative TheoreticalModel

Figure 1 shows my proposed integrative theoreticalmodel. As explained below, this theory combines andintegrates not only the contents of, and literature cited by,Valla and Ceci, Schmidt, von Stumm et al., and Nye et al.,but also: (a) the Ackerman (1999) findings showing a pos-itive correlation between both Introversion and TIE andacquisition of general knowledge over time, (b) Cattellsinvestment theory of intelligence with its constructs of

fluid intelligence and crystallized intelligence (Cattell,1971, 1987), (c) recent research showing that crystallized

Introversion

Crystallized Intelligence-

General and Specific

Knowledge and Skills

(gc)

Interest in

General Learning

(TIE)

Mental Functioning

at Older Ages

Adult Academic and

Occupational

Performance

Specific

Interests

Fluid

Intelligence(gf)

Conscientiousness

Prenatal

Harmonal

Conditioning

Fig. 1. A general integrative theoretical model for individual differences variables. (Variables are as defined in the text.)



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intelligence is a much better predictor of real worldperformances and achievement than fluid intelligence(Postlethwaite, 2011), and (d) Goldbergs (2005) neuro-science based research and theory explaining howpeople maintain high levels of intellectual and occupa-tional performance long past ages at which fluid mentalability has declined to relatively low levels. This scopeencompasses a large number of research literaturesacross multiple areas of the psychology of individualdifferences. An explanation of this theoretical modelfollows.

Introversion, TIE, and acquisition of

general knowledge

In a large study of adults, Ackerman and his associates(Ackerman, 1999; Goff & Ackerman, 1992; see alsoAckerman, 1996) presented evidence that Introversionwas positively correlated with TIE (or, alternatively, that

Extroversion was negatively correlated with TIE). Theyalso found that both Introversion and TIE are substan-tially positively correlated with level of general knowl-edge acquired over time. The knowledge measures usedvaried widely and included (a) five tests in the physicalsciences and math; (b) five tests in the social sciences,law, and business; (c) three tests in history and Westerncivilization; (d) four tests in art and literature; and (e)three tests in technology and tools. Both Introversion andTIE were substantially positively correlated with scoreson each one of these 20 knowledge tests. To state thisdichotomously, introverts and high TIE people acquire ahigher level of generic knowledge over time than doextroverts and low TIE people, possibly because theyspend more time reading, thinking, and reflecting, andspend less time in social interactions. The average TIEcorrelation with the 20 knowledge tests (mean r =.35) islarger than the average correlation for Introversion (meanr = .27). (Both these correlations are larger at the con-struct level because they have not been corrected for thedownward bias created by measurement error.) The rela-tive size of these correlations is consistent with the modelin Figure 1, because in the model TIE is a direct cause ofcrystallized intelligence whereas Introversion is an indi-rect cause, with its effect being mediated through TIE.

In the model shown in Figure 1, both Introversion andfluid intelligence exert causal effects on TIE. A relatedand theoretically relevant research finding is this: Intereststend to be positively correlated and the general factorunderlying these intercorrelations correlates .48 with TIE(Ackerman & Heggestad, 1997, p. 235). Scores on thisgeneral factor reflect breath of interests, just as TIE does.This research also found that this composite interestscore (general factor score) correlates positively and sub-stantially with scores on each of the 20 knowledge tests,

with most values in the .30 to .35 range. The pattern ofcorrelations with knowledge scores is quite similar to thatof TIE. It is likely that a combination of TIE scores andscores on this general interest factor is a better measureof interest in general learning than the TIE scale alone. Indiscussing the model in Figure 1, the TIE symbol is usedmerely as a convenient label for interest in general learn-ing. There is no evidence of a sex difference in TIE, andthe Roznowski (1987) study (summarized in Schmidt,2011) provides evidence for the absence of a TIE sex dif-ference. Based on a large sample, that study found thatthe general level of knowledge acquisition over time isthe same for males and females, albeit the distribution ofacquisition across knowledge categories is differentbetween the sexes.

Fluid and crystallized intelligence

Fluid intelligence, TIE, and specific interests exert causal

influences on the development of crystallized intelli-gence, which is defined in Cattells investment theory asacquired knowledge and skills. Crystallized intelligenceis a broad category; it includes skills such as math knowl-edge, mechanical knowledge, word knowledge, knowl-edge of history, and so on. Cattells theory states thateach individual has an initial level of fluid intelligence(thought to be genetically and neurologically based),and people invest their fluid ability in the developmentof a wide variety of knowledge, skills, and aptitudes,with these investments being guided by their interests,both specific and general. TIE is the broadest of theseinterests, and the specific interests include those exam-ined in Nye et al., Schmidt, and Valla and Ceci. TheSchmidt article postulates that technical interests causetechnical knowledge and ultimately cause increases intechnical aptitude. Ackerman (1996, 1999; Ackerman &Heggestad, 1997) presents evidence that three of the sixHolland interest types contribute to generic knowledgeacquisition: Investigative, Realistic, and Artistic interestareas.

Sex differences in interests

As depicted in Figure 1, specific interestsat least some

of themare influenced in the case of males by prenatalhormonal conditioning (exposure to testosterone), aspostulated by Valla and Ceci and Ceci et al. (2009). Inparticular, prenatal hormonal conditioning predisposesmore males than females toward interest in inanimatethings (i.e., physical phenomena) and more females thanmales toward interest in people and other living things.The categories of things and people each encompass anarray of more specific interests. The broad area of interestin inanimate things includes STEM-related interests (as



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216 Schmidt

discussed in Valla and Ceci) and technical interests (asdiscussed in Schmidt).

Academic and occupational

achievement

The theory postulates that the major determinant of adultacademic and occupational achievement is crystallizedintelligence. Postlethwaite (2011) recently presented con-siderable evidence, based on extensive meta-analyses,that crystallized intelligence measures have considerablyhigher validity than fluid ability measures for predictingnot only academic performance but also occupationaland job performance. Typically, fluid intelligence mea-sures add little or nothing to prediction of either aca-demic or job performance beyond the validity ofcrystallized intelligence measures. This finding supportsthe conclusion that acquired knowledge and mental skillsare superior to supposed measures of initial innate men-

tal endowment in determining real world performancesand, more broadly, occupational success in life.

The other two variables exerting causal effects onadult academic and occupational performance are thepersonality trait of Conscientiousness and specific inter-ests. The effect of specific occupational interests wasdemonstrated in the Nye et al. (2012) study, whichshowed that this effect is strongest when the individualsstrongest interests are matched with a work or academicenvironment supportive of those interests. An examplewould be someone with strong social interests findinghimself or herself in a social occupation such as K12school teaching or social work. The causal impact of spe-cific interests will be strong to the extent that people aresuccessful in finding college majors and work environ-ments that match and support their strong specific occu-pational interests. The von Strum et al. article demonstratesthat Conscientiousness contributes to academic success,controlling for the effects of intelligence and TIE. Asdepicted in Figure 1, TIE exerts an indirect, rather thandirect, effect on academic (and work) success in the pres-ent theory, with its effect being mediated through crystal-lized intelligence. There is a large literature showing thatConscientiousness predicts job and occupational perfor-mance, controlling for the effects of mental ability (e.g.,

see Schmidt, Shaffer, & Oh, 2008). Much of this researchis cited in von Stumm et al.

Finally, we have the neuroscience based research andtheory of Goldberg (2005). Goldberg operated within theconceptual framework of Cattells theory of intelligence.He was struck by the massive research evidence thatfluid intelligence, considered to be the ability basis forlearning in general, declines over time as the individualages and has declined fairly substantially by the timepeople enter their 50s. At the same time he noted the

evidence that many, if not most, people achieve theirmost important intellectual and occupational contribu-tions after age 50 and often later. He set out to explainthis apparent contradiction. His research on skilled men-tal performances of people 50 and older supported theconclusion that these achievements in middle age andlater are explained by the use of templates, mental strate-gies, or decision rules or patterns that were built up andstored gradually over time; that is, these achievementsare made possible by use of accumulated crystallizedintelligence skills that had originally required fluid men-tal ability for their acquisition but now operate indepen-dently of current levels of fluid intelligence. The story inhis theory is one of using fluid intelligence over a lifetimeto build up skills, knowledge, and problem-solving strat-egies based on pattern recognition that constitute exper-tise that can be successfully employed well into olderages and long after fluid intelligence had declined mark-edly. Knowledge, skills, and strategies are all forms of

crystallized intelligence within the framework of Cattellstheory. Thus the theoretical model in Figure 1 indicatesthat the key determinant of level of mental functioning asan older adult is crystallized intelligence. This finding isconsistent with the research findings of Ackerman (1999)and the results obtained by Postlethwaite (2011).

The Present Theoretical Integration

This theory accounts for many research findings in theareas of personality, interests, mental abilities, knowledgeand skill acquisition, academic performance, job perfor-mance, and career success. However, it could perhaps becriticized on grounds that it is not sufficiently parsimoni-ous. But theoretical parsimony may have its limits whenthe subject is as complex as the behavior and perfor-mance of humans. This theory may represent the maxi-mum parsimony that is possible in the explanation of thefunctioning of these complex individual differencesvariables.

Causal models or theories of complex phenomena arealways approximations, but a model is useful if it cap-tures the predominant flows of causality. Even then amodel can perhaps be extended to be more complete.The present model intentionally considers only the case

of normal male levels of prenatal exposure to testoster-one. It is possible that extreme levels of prenatal expo-sure produce not only an extreme orientation of interestsaway from people and other living things and towardinanimate objects and phenomena, but also the kind ofextreme introversion seen in autistics. It is possible thatsubclinically autistic individuals tend to gravitate towardthe STEM fields. These ideas suggest a possible way inwhich the model might be extended. Based on the find-ings of Ackerman and his associates (cited earlier), this



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model postulates that introversion is a cause of TIE.Another possibility is that TIE is a cause of introversion.However, personality traits emerge and congeal at ayoung age and are apparent in early childhood, whereasTIE becomes apparent only somewhat later, perhapsaround age 8 at the earliest for some and around adoles-cence for most. So for that reason, there is probably astronger case for introversion being a cause of TIE.However, this is a question for research.

In the model, no variables are postulated as causes orprecursors of fluid intelligence and Conscientiousness.However, these variables do have causes. Studies inbehavior genetics have shown that both personality traitsand mental abilities (including fluid intelligence) arestrongly genetically influenced (cf. Bouchard, 1997a,1997b; Bouchard & McGue, 1981; Holden, 1987). Asshown in Bouchard (1997a), this is also true of vocationalinterests and attitudes toward work. In the case of the non-cognitive traits, heritabilities are typically around .40. The

square root of the heritability is the correlation betweengenes and the trait; the square root of .40 is .63a sub-stantial correlation. Heritabilities are considerably higherfor mental abilities, typically in the .50 to .80 range. Sothere are both genetic and environment precursors ofthese traits, and these could be listed in the model. Whatabout the role of the individuals experience? It turns outthat experience itself is genetically influenced, becausepeople tend to create their own environments and experi-ences based on proclivities and propensities that aregenetically influenced (cf. Plomin & Bergman, 1991; Scarr,1996; Scarr & McCartney, 1983). In the model presentedhere, both TIE and specific interests are traits that leadpeople to create the experiences that shape the amountand type of crystallized intelligence the individual attains.So there is a role in the model for experience.

Summary

This article integrates the findings of four recent articlesappearing in Perspectives on Psychological Science (Nyeet al., 2012; Schmidt, 2011; Valla & Ceci, 2011; von Stummet al., 2011) and related findings in the literature to producea general theoretical model of the causal relationshipsamong abilities, general and specific interests, and person-ality traits in the production of adult academic and occupa-tional achievement and mental functioning in old age. Thetheory postulates a causal process that explains the lowerrepresentation of women in STEM occupations as beingcaused by sex differences in interest in these occupationsand not by any difference in relevant abilities.

Declaration of Conflicting Interests

The author declared no conflicts of interest with respect to theauthorship or the publication of this article.

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the role of personality and general mental ability in joband training performance.Personnel Psychology, 61, 827868.

Su, R., Rounds, J., & Armstrong, P. I. (2009). Men and things,women and people: A meta-analysis of sex differences ininterests.Psychological Bulletin, 135, 859884.

Valla, J. M., & Ceci, S. J. (2011). Can sex differences in science

be tied to the long reach of prenatal harmones? Brain orga-nization theory, digit ratio (2D/4D), and sex differences inpreferences and cognition. Perspectives on PsychologicalScience, 6, 134146. doi:10.1177/1745691611400236

von Stumm, S., Hell, B., & Chamorro-Premuzic, T. (2011). Thehungry mind: Intellectual curiosity is the third pillar of aca-demic performance. Perspectives on Psychological Science,6, 574588. doi:10.1177/1745691611421204


Documents

Schmidt (2014, PS) - A General Theoretical Integrative Model of Individual Differences.pdf