In research on individual differences, vocational interests play an important role. Although such interests have typically received less attention than cognitive ability and personality, they are often considered to be the third pillar of individual differences (Chamorro-Premuzic,
2007). Initially, it was assumed that vocational interests mainly influence decisions regarding what to study or which occupation to enter. However, more recent research has shown that interests also relate to performance in one’s chosen direction (Nye et al.,
2012; Van Iddekinge et al.,
2011). In general, interests have motivational properties influencing the direction of activities, the level of energy invested in them, and the persistence in the activities. All three aspects are direct determinants of job performance (Su,
2012).
The General Factor of Personality
Most currently known personality models, such as the Big Five, the Giant Three, or the HEXACO model, assume multiple, independent personality dimensions. Yet, meta-analyses have clearly confirmed that these dimensions consistently correlate, indicating that they share a relevant proportion of their variance. This shared variance captures the socially desirable ends of the underlying scales (e.g., Musek,
2017; Rushton & Irwing,
2011; Van der Linden et al.,
2010a,
2016). For example, in terms of the Big Five, a general factor emerges that implies that high-scoring individuals seem to be relatively open-minded, hard-working and reliable, sociable, friendly, and emotionally stable. The general factor has not only been identified in the Big Five, but also in virtually every other personality model, such as Eysenck’s three-factor model, the six-factor HEXACO, or in the California Personality Inventory (Loehlin, 2012). Moreover, a GFP even emerges when using a personality type approach (Gerlach et al.,
2018).
It does not really matter which personality model (e.g., Big Five, HEXACO, PEN) or instrument (NEO, BFI, CPI) one uses to extract a GFP, because the resulting general factors will be highly similar (e.g., Loehlin & Horn,
2012; Rushton & Irwing,
2011; Van der Linden et al.,
2016). The only condition is that a sufficiently broad range of personality traits is taken into account so that the GFP truly reflects a mix of different traits. Thus, the principle of the “indifference of the indicator” (Jensen,
1998) also applies to the GFP. As an illustration, the direct correlations between general factors from different personality models/instruments is around
r = 0.60 (e.g., Loehlin & Horn,
2012; Van der Linden et al.,
2011). More sophisticated modeling showed that the associations between GFPs extracted from different comprehensive personality measures reaches unity (Rushton & Irwing,
2011).
The GFP is not only robust regarding model or instrument, but also regarding statistical method: Different ways of extracting the GFP all lead to nearly identical results (Van der Linden et al.,
2017). This makes sense, because the different statistical methods, at the end, capture the shared variance among personality traits. Thus, exploratory factor analytic techniques, such as principal axis factoring, or more complex confirmatory modeling techniques, lead to GFPs that typically correlate in the range of
r = 0.90 to 1.00. It also does not make a conceptual difference whether one will test hierarchical or bi-factor models. Crede and Harms (
2015) stated that “…admittedly, one of the superior alternative models, the bi-factor model (BFM), would result in an interpretation that is similar to that arising from the higher-order factor model” (p. 857).
Although the existence of a GFP is now beyond reasonable dispute, there is an ongoing scientific debate regarding its presumed nature. Initially, some scholars considered the GFP to mainly reflect methodological artifacts, such as response tendencies or an inflated sense of self when filling out self-reports (Bäckström et al.,
2009; Connelly & Chang,
2016; Revelle & Wilt,
2013). Other scholars suggested that the general factor may be a statistical artifact caused by correlations at the facet level (Ashton et al.,
2009). If such artifact explanations are valid, then the GFP does not reflect a person’s ‘true personality’, but would merely be a nuisance in personality assessment.
In contrast is the notion that the GFP is substantive and reflects a genuine trait (Figueredo et al.,
2004; Musek,
2007; Rushton et al.,
2008). The currently leading substantive interpretation is that it reflects general social effectiveness (Dunkel & Van der Linden,
2014; Loehlin,
2011; Van der Linden et al.,
2016). In this view, high-GFP individuals are characterized by having social knowledge and skills that help them obtain their goals.
Several lines of empirical findings fit with the social effectiveness account of the GFP. For example, high-GFP individuals do better on ability tests of social knowledge and skills (Van der Linden et al.,
2014), the GFP strongly overlaps with measures of emotional intelligence (Anglim et al.,
2019; Van der Linden et al.,
2017), and it is related to various positive social outcomes such as likability/popularity and leadership (Van der Linden et al.,
2010b; Wu et al.,
2020). The GFP has also been linked to a range of other-rated or objective outcomes in which social effectiveness is assumed to play a role, such as job performance (Pelt et al.,
2017). Importantly, several of these previous studies showed that the GFP drives the lion’s share of the criterion-related validity of lower-order factors such as the Big Five, or HEXACO (see, for example, the meta-analytic reports of Pelt et al.,
2017).
The various arguments and pieces of evidence in the artifact versus substantive views have been extensively addressed in many previous articles and therefore will only be briefly summarized here. One of the key points is whether the GFP is restricted to self-reports, as can be expected from a measurement artifact, or whether it also relates to other-rated or objective outcomes, which would be in line with the substantive account. Above, we already referred to studies that have confirmed that the GFP indeed relates to other-rated and objective outcomes. Moreover, GFPs extracted from self-reports substantially overlap with GFPs extracted from other-ratings of personality (Oltmanns et al.,
2018; Rushton et al.,
2008). Some studies seemed to suggest that there is no overlap on GFPs from self and other ratings (e.g., Chang et al.,
2012). However, in each of these cases, close scrutiny of the paper reveals that debatable controls were used to make the general factor “disappear”, and by doing so, the studies may have taken away much (if not all) of the true variance of the GFP (Van der Linden et al.,
2021).
Ashton et al. (
2009) proposed an alternative model, in which correlations between facets are merely causing the impression of higher-order factors above the six HEXACO dimensions. Subsequently, they showed that no higher-order factors appear when controlling for facet-level correlations. This approach, however, does not explain what may cause the intercorrelations between facets or why theoretical explanations at the facet level should have precedence over explanations assuming higher-order factors (Van der Linden et al.,
2016).
Finally, there is evidence showing that removing the socially desirable component of personality items decreases the size of the GFP (Bäckström et al.,
2009). The limitation of that approach is that it remains unclear whether one can remove socially desirable content without changing the nature of the items and losing their criterion-related validity (e.g., whether it still predicts job performance). Moreover, even though the GFP is reduced in size with this approach, it does not completely disappear. In fact, the authors that originally tested the effect of social desirability on the GFP recently acknowledged that a relevant (substantive) general factor seems to be present in personality measures (Bäckström et al.,
2020).
In conclusion, although the last word in the GFP debate has not been spoken, there is sufficient evidence suggesting that the substantive account is a reasonable hypothesis that needs further testing. Yet, if the GFP indeed would be substantive, then a subsequent question is, why would it be useful to pay attention to such a general factor? One theoretical reason for doing so is that it might partly explain why so many previous meta-analyses with, for example, the Big Five, have found relations to outcomes, such as job performance, self-esteem, psychopathology, and many others (Oltmanns et al.,
2018; Oshio et al.,
2018; Pelt et al.,
2017), in a pattern of O + , C + , E + , A + , and N − . Such a common pattern could be partially and parsimoniously explained by the GFP as the driving force behind the associations found. Another possible advantage of the GFP is that it might be able to unify various theories or models of individual differences. For example, it has been used to integrate the literature on personality and emotional intelligence by arguing that emotional intelligence may exert influence on most of the specific personality dimensions, thereby causing their intercorrelations (Van der Linden et al.,
2017). The practical relevance of the GFP includes that it has found to be relevant for personnel selection (Pelt et al.,
2017) and that it has clinical relevance because low scores indicate a range of psychological problems (Oltmanns et al.,
2018).
The GFP and Vocational Interest
One imperative reason for examining the link between the GFP and vocational interests is that it provides a novel way of testing the social effectiveness hypothesis. Specifically, it can be expected that people tend to have a preference for activities and occupational areas in which they can excel (Nye et al.,
2012; Su,
2012). Someone who has a talent or is skilled in calculations would, on average, be interested in professions or activities in which those skills and talents can be used. In the same line of reasoning, if a person would be socially effective, it can be expected that they prefer occupations in which they can express their social skills that are presumably central to the GFP.
Accordingly, it can be expected that the GFP would be particularly related to vocational areas that more strongly rely on social interactions. Being socially effective may be helpful in almost any job, but various vocational interest models clearly point to some areas in which social effectiveness is more salient and/or important (Su,
2012). One of the most prominent interest models is Holland’s RIASEC model, which distinguishes six basic higher-order factors of vocational interests, namely realistic, investigative, artistic, social, enterprising, and conventional interests (Holland,
1997). Particularly, the social and enterprising interests are related to preferences in working with people or achieving success by means of social interactions, respectively (Berings et al.,
2004; Su,
2012). The other dimensions in the model more strongly refer to working with things (e.g., realistic) or ideas (e.g., investigative). Thus, in the Holland model, it can be expected that the GFP may particularly relate to those dimensions in which social interactions play an important role.
If the GFP would only represent response bias or socially desirable responding, it would not be obvious why it would be particularly related to occupations with stronger social components, unless people who have a tendency to fake higher scores on socially desirable personality traits may also have a tendency to fake more interest in social desirable occupations. In that case, the resulting GFP–interests correlation would still reflect artifact. However, there are no studies suggesting that social or enterprising interests are more socially desirable compared to, for example, artistic or investigative interests. Indeed, studies on occupational prestige suggest that social occupations often are accompanied with lower payment and prestige compared to, for instance, technical jobs (Bose & Rossi,
1983; Duncan,
1961).
A second reason for including the GFP is to gain more fundamental insight into the relationship between personality and vocational interests. Previous studies and meta-analyses on this topic have, without exception, considered the personality dimensions under study mostly as conceptually independent traits (Larson et al.,
2002; Mount et al.,
2005). This approach has theoretical and analytical consequences. Theoretically, it implies that one has to develop separate explanations for each specific relationship between a certain personality trait and an interest, whereas there may be more general processes involved that have a broader influence on multiple traits. Thus, the GFP potential may contribute to a deeper understanding of what drives the overlap between traits and interests.
Analytically the “separate trait approach” often leads to researchers adopting regression analyses, in which the shared variance of the personality dimensions has been taken out of the equation (i.e., the regression controls for the overlap). This means that one actually examines the residuals of the personality dimensions (for example those aspects of extraversion or openness that are not shared with other traits) instead of how the traits were initially measured. Yet, from a GFP point of view, the shared variance between traits is relevant, or even crucial, and omitting it would dismiss part of the driving force behind the relationship between personality and vocational interests. In the present research, we will address the topics outlined above in four large datasets, including different measures of personality and vocational interests.
Study 2: Vocational Interests in Project Talent
Study 2 was conducted as a conceptual replication and addressed the limitations of study 1. We used data from Project Talent, which is a well-known and large study from the 1960s in which roughly 5% of the entire US high-school population was sampled (American Institute for Research, Project Talent, 1960). We focused on the data in the last year of high school in which vocational interests may have been more strongly developed and were also the most relevant, because they directly relate to the educational or vocational choices in the subsequent year. Another advantage of having high-school students as participants is that they were not yet strongly exposed to working life (although some students may have had part-time or summer jobs). This largely addressed a possible alternative causal explanation being that the profession one works in influences personality as well as vocational interest (i.e., reversed causation). Lastly, an additional asset of the Project Talent data was that it included cognitive tests, which allowed for the extraction of a general cognitive ability factor. Cognitive ability is known to relate to vocational interests, for example, higher cognitive ability has been shown to relate to more complex (e.g., computer programming) or investigative jobs (Pässler et al.,
2015).
In addition, several studies suggest that there may be a positive correlation between cognitive ability and the GFP (e.g., Dunkel et al.,
2014). Similar to our lines of reasoning on gender as a control variable, we consider cognitive ability a relevant control variable to examine. For example, based on the literature, there is the possibility that cognitive ability may be “the hidden variable” that relates to the GFP as well as vocational interest. In that case, the GFP–vocational interest association would be spurious and disappear or otherwise substantially diminished after controlling for cognitive ability. Alternatively, cognitive ability might also be a statistical suppressor of the true GFP–interests associations and controlling for it would then increase the associations. Another option is that despite their possible intercorrelation, the GFP and cognitive ability may mostly influence unique parts of the variance in vocational interests. If that is so, controlling for cognitive ability would not have strong effect on the GFP–interest associations. Again, the current literature is not conclusive about these possibilities, and for reasons of transparency, we consider it informative to report the direct associations between the GFP and vocational interests as well as those after controlling for cognitive ability. Overall, the main aim of study 2 was to conceptually replicate the relationship between the GFP and interests in jobs and activities (in the “
Method” section, the specific interest dimensions are explained) with a different set of personality and interests measures.
Method
Sample
In study 2, the sample was drawn from the Project Talent (
https://www.icpsr.umich.edu/web/NACDA/studies/33341), which was a large national-wide study in the USA that in the 1960s started surveying high school students from 1353 schools across the country. A full description of the procedures and test constructions is provided by Flanagan (
1962). For the reasons provided in the “Introduction” section of study 2, we used the sample from the last year of high school. In this sample (
N = 81,130), the mean age of the participants was 17.25 years (
SD = 1.78). 48.9% were male and 51.1% female.
Results
The existence of the GFP in Project Talent has already been confirmed by the study of Dunkel et al. (
2014), who tested the relationship between personality and general cognitive ability. In the present study, we used the same extraction method, namely the first unrotated factor obtained with principal axis factoring. The GFP in this dataset explained no less than 61.38% (eigenvalue
[EV] = 6.14) of the variance in the specific scales. The general factor loaded on each of the scales in the expected direction (i.e., towards social desirability/effectiveness). The mean loading was 0.75. The specific factor loadings were 0.77, 0.79, 0.78, 0.56, 0.69, 0.83, 0.75, 0.77, 0.83, and 0.76 for, VI, CA, MA, IM, SC, CU, SO, LE, SE, and Ti, respectively.
We went beyond Dunkel et al. (
2014) by also testing the viability of the GFP in Project Talent using CFA. The details of those analyses are reported in the supplementary material (
S1). As a summary, the direct model, in which the GFP loaded on each of the scales, showed an acceptable fit when looking at the CFI and TLI indices (0.93 and 0.91, respectively), but the RMSEA was suboptimal (0.11). Further examination showed that the unique variances of several specific personality scales correlated beyond the general factor. Accordingly, when allowing six correlations between the unique scale variances, the fit improved (CFI = 0.97, TLI = 0.95, RMSEA = 0.08). Note that allowing those additional correlations had an effect on the fit, they hardly had an effect on the nature of the GFP and its factor loadings (still ranging from 0.55 to 0.84,
MLoading = 0.75). More importantly, the latent GFP from the CFA correlated
r = 0.99 with the GFP extracted by means of PAF as described by Dunkel et al. (
2014). Alternative models that did not include a general personality factor showed worse fit (see S1).
GFP and Vocational Interests
Table
5 shows the zero-order correlations between the study’s variables. Due to the very large sample size, we do not report significance levels as they are not informative and mainly effect sizes are relevant. The correlations in Table
5 reveal that the GFP was positively associated with the broad interest factor “Working with People”, whereas the correlation with the factor “Interests in Things” was rather low.
Table 5
Zero-order correlations between the variables in study 2
1. Sex | 1 | | | | | | | | | | | | | | | | | | | | | |
2. Age | − 0.12 | 1 | | | | | | | | | | | | | | | | | | | | |
3. GFP | 0.14 | − 0.08 | 1 | | | | | | | | | | | | | | | | | | | |
4. g factor | − 0.07 | − 0.20 | 0.14 | 1 | | | | | | | | | | | | | | | | | | |
5. Things | − 0.75 | 0.09 | − 0.08 | 0.11 | 1 | | | | | | | | | | | | | | | | | |
6. People | 0.35 | − 0.09 | 0.25 | 0.10 | 0 | 1 | | | | | | | | | | | | | | | | |
7. Physical, science, engineering, mathematics | − 0.40 | − 0.01 | 0.09 | 0.30 | 0.68 | 0.20 | 1 | | | | | | | | | | | | | | | |
8. Biological medicine | − 0.07 | − 0.05 | 0.18 | 0.23 | 0.32 | 0.44 | 0.71 | 1 | | | | | | | | | | | | | | |
9. Public service | − 0.23 | − 0.02 | 0.15 | 0.15 | 0.48 | 0.60 | 0.55 | 0.50 | 1 | | | | | | | | | | | | | |
10. Literary-linguistic | 0.24 | − 0.08 | 0.23 | 0.21 | − 0.01 | 0.77 | 0.44 | 0.58 | 0.55 | 1 | | | | | | | | | | | | |
11. Social service | 0.40 | − 0.06 | 0.24 | 0.09 | − 0.21 | 0.68 | 0.27 | 0.51 | 0.39 | 0.72 | 1 | | | | | | | | | | | |
12. Artistic | 0.20 | − 0.05 | 0.18 | 0.20 | 0.05 | 0.59 | 0.44 | 0.54 | 0.41 | 0.76 | 0.58 | 1 | | | | | | | | | | |
13. Musical | 0.19 | − 0.04 | 0.17 | 0.15 | − 0.03 | 0.51 | 0.33 | 0.44 | 0.33 | 0.68 | 0.54 | 0.65 | 1 | | | | | | | | | |
14. Sports | − 0.26 | 0 | 0.13 | 0.17 | 0.51 | 0.21 | 0.59 | 0.50 | 0.51 | 0.45 | 0.41 | 0.43 | 0.33 | 1 | | | | | | | | |
15. Hunting and fishing | − 0.40 | 0.04 | 0.05 | 0.16 | 0.58 | − 0.01 | 0.53 | 0.41 | 0.38 | 0.25 | 0.15 | 0.31 | 0.21 | 0.64 | 1 | | | | | | | |
16. Business management | -0.19 | 0.01 | 0.16 | 0.12 | 0.46 | 0.53 | 0.57 | 0.50 | 0.70 | 0.60 | 0.54 | 0.50 | 0.37 | 0.60 | 0.43 | 1 | | | | | | |
17. Sales | -0.14 | 0.03 | 0.11 | 0.06 | 0.37 | 0.47 | 0.44 | 0.39 | 0.56 | 0.51 | 0.47 | 0.44 | 0.32 | 0.50 | 0.36 | 0.77 | 1 | | | | | |
18. Computation | -0.01 | 0.01 | 0.12 | 0.10 | 0.19 | 0.41 | 0.50 | 0.36 | 0.43 | 0.42 | 0.50 | 0.35 | 0.28 | 0.43 | 0.24 | 0.65 | 0.59 | 1 | | | | |
19. Office work | 0.45 | -0.01 | 0.12 | -0.06 | -0.33 | 0.44 | 0.05 | 0.14 | 0.14 | 0.41 | 0.61 | 0.35 | 0.30 | 0.20 | -0.02 | 0.40 | 0.40 | 0.63 | 1 | | | |
20. Mechanical technical | -0.54 | 0.10 | -0.03 | 0.11 | 0.85 | -0.07 | 0.73 | 0.44 | 0.42 | 0.21 | 0.14 | 0.29 | 0.17 | 0.59 | 0.62 | 0.55 | 0.47 | 0.41 | 0.06 | 1 | | |
21. Skilled trades | -0.29 | 0.11 | -0.02 | 0.01 | 0.65 | 0.07 | 0.52 | 0.37 | 0.38 | 0.32 | 0.35 | 0.38 | 0.26 | 0.58 | 0.54 | 0.58 | 0.56 | 0.47 | 0.31 | 0.81 | 1 | |
22. Farming | -0.25 | 0.06 | 0.03 | 0.12 | 0.54 | 0.05 | 0.49 | 0.40 | 0.34 | 0.32 | 0.30 | 0.38 | 0.26 | 0.59 | 0.67 | 0.46 | 0.42 | 0.31 | 0.14 | 0.63 | 0.68 | 1 |
23. Labor | -0.30 | 0.12 | -0.03 | 0.01 | 0.61 | 0.04 | 0.45 | 0.30 | 0.35 | 0.28 | 0.30 | 0.29 | 0.22 | 0.52 | 0.50 | 0.56 | 0.54 | 0.43 | 0.28 | 0.71 | 0.84 | 0.63 |
With regard to the 17 more specific interest factors, and in line with expectations, the GFP showed correlations of
r ≥ 0.15 with the clearly social occupational areas of business and management, public services, and social service. In the context of this study, the GFP’s higher correlations with biological/medicine, linguistic, musical, and artistic occupations may initially seem less obvious. Yet, in previous research, those latter four occupational categories have been shown to be subsumed under the broader category of working with people (i.e., show higher loadings on the “People factor” than on the “Things factor”, e.g., Su,
2012).
Similar to study 1, there were relevant relations between gender and vocational interests. Noteworthy is the rather strong negative correlation (
r = − 0.75) between gender and the broad interest factor of “Interest in Things”. Females, on average, scored lower on this factor (Su et al.,
2009). General cognitive ability showed several associations with vocational interests too. Most of these were positive, the exception being Office work. The two strongest correlations were with hard sciences and engineering, and with life sciences. However, cognitive ability was also positively associated with interests, such as linguistic, artistic, and sport activities.
The partial correlations are reported in Table
6 and show that even after controlling for gender and cognitive ability, the pattern of results remained largely the same. Thus, the findings regarding the link between the GFP and social interests were not merely “a by-product” of gender or cognitive ability.
Table 6
Partial correlations (controlling for sex and general cognitive ability) between interests and the GFP (N = 78,436)
Things (factor) | 0.04 |
People (factor) | 0.20 |
Physical science, engineering, mathematics | 0.09 |
Biological Science, medicine | 0.14 |
Public Service | 0.15 |
Literary-Linguistic | 0.15 |
Social Service | 0.17 |
Artistic | 0.09 |
Musical | 0.10 |
Sports | 0.13 |
Hunting and Fishing | 0.06 |
Business and Management | 0.16 |
Sales | 0.09 |
Computation | 0.08 |
Office Work | 0.03 |
Mechanical-Technical | − 0.01 |
Skilled trades | − 0.04 |
Farming | 0.00 |
Labor | − 0.05 |
Table 7
Correlations between the PTPI dimensions and interests, and the unique variances (between brackets) of the PTPI dimensions and interests
Socioability | − 0.08 (− 0.03) | 0.17 (− 0.03) |
Social sensitivity | − 0.17 (− 0.18) | 0.26 (0.09) |
Impulsiveness | 0.02 (0.07) | 0.06 (− 0.09) |
Vigor | 0.08 (0.21) | 0.12 (− 0.12) |
Calmness | − 0.02 (0.07) | 0.16 (− 0.06) |
Tidiness | − 0.16 (− 0.16) | 0.19 (0.00) |
Culture | − 0.19 (0.23) | 0.31 (0.19) |
Leadership | 0.02 (0.12) | 0.20 (0.00) |
Self-confidence | 0.01(0.09) | 0.12 (− 0.07) |
Mature personality | − 0.03(0.06) | 0.20 (0.02) |
Table 8
Percentages of explained variance (R2Δ) in Interest in Things and people, by the GFP and the combined (10) unique variances of the PTPI dimensions
Things | < 0.01 | 503.06 | 0.13 | 1213.37 |
People | 0.06 | 5121.88 | 0.05 | 536.95 |
The GFP Versus the Specific Personality Scales
As in study 1, we included a test showing the relative contribution of the general factor versus the unique variances of the ten specific personality scales of the PTPI. In doing so, for clarity, we restricted the analyses to the two broad interest categories, things and people. First, we calculated the correlations of each PTPI scale with those categories. Table
7 shows that each of the scales was positively related to interest in working with people (low impulsivity showed the weakest correlation and culture the strongest correlation). However, when only considering the unique variance of the scales—after having taken out the GFP—it is clear that almost all of these correlations became either very small or even reversed sign and became negatively related to interest in working with people. The only exception was culture, which went from
r = 0.31 to 0.18. A regression with interest in people as the dependent variable, the GFP as a predictor in the first step, and the unique variances of the ten specific scales in step 2 further confirmed the influence of the GFP. Specifically, in the first step, the GFP as a positive predictor explained 6.1% of the variance in people interest. The 10 unique variances in step 2 became a negative predictor of people interest and explained a smaller proportion of the variance, 5.4% (see Table
8).
Discussion
In the large sample of Project Talent, study 2 showed conceptual replication by using entirely different personality and vocational interest measures compared to study 1. Again, the GFP was clearly positively related to a preference for working with people and was not relevantly related to a preference for working with things. Similar to study 1, the results were robust after controlling for gender, and the findings also remained stable after controlling for general cognitive ability.
Regarding the specific vocational interest dimensions, the strongest relationships with the GFP were among those that can reasonably be expected to have more social components, such as public and social services, and business and management (Rosenbloom & Ash, 2004). The GFP also showed relevant associations with several interest dimensions that would seem less obvious from the social effectiveness perspective, such as literary-linguistic activities and occupations. Su (
2012), however, showed that in the Project Talent sample, library science is substantially related to interest in working with people. Thus, in this respect, the correlations between those interests and the GFP fit with the general notion that the GFP particularly relates to jobs with a strong “people” component.
In study 2, it was also replicated that the GFP and a general factor in vocational interests showed a correlation that is not in line with the bias or artifact interpretation. The correlation was r = 0.13, whereas a much more substantial correlation of r ≈ 0.50 may be expected if both would have reflected similar response biases or general artifacts.
The comparisons between the relative impact of the shared variance of the personality scales, i.e., the GFP, versus their unique variance also led to as similar picture as in study 1. When it came to interest in working with people, the GFP explained most of the variance. Beyond that, the total unique variances of the specific scales added a smaller, but still relevant part of the variance in people interest. However, the unique variances of the scales were mainly negative predictors of interest in working with people. Those set findings iterate that a large component of the relations between personality scales and interest in social occupations may be due to the general factor.
Study 3: Testing the Genetic Correlations
After the findings from studies 1 and 2, a subsequent logical step was to examine the extent to which phenotypical associations between the GFP and vocational interests are at the genetic level. In the introduction, we mentioned that the heritability of the GFP has already been confirmed in several studies that used twin data (Loehlin,
2011; Figueredo & Rushton,
2009; Van der Linden et al.,
2018; Veselka et al.,
2009). An initial study of Power and Pluess (
2015) that used genome-wide data, casted some doubts on whether the correlations between the Big Five are also revealed at the genetic level. This is relevant because if there would be no genetic Big Five intercorrelations then that would make it difficult to uphold that there is a genetic GFP. The study of Power and Pluess, however, was based on a relatively small sample for genome-wide analyses. Moreover, many of their estimates did not converge and they could also not confirm the basic heritabilities of several of the Big Five dimensions. In contrast, a more recent genome-wide study of Lo et al. (
2017), using a much larger dataset, did confirm the Big Five intercorrelations at the genetic level. In fact, the (absolute) genetic correlations in Lo et al.’s study ranged from |0.11| to |0.40|, with a mean intercorrelation of
r = 0.232, which was remarkably similar to the meta-analytic phenotypical Big Five intercorrelations reported by Van der Linden et al., (
2010a,
2010b), which had a mean observed (uncorrected) Big Five intercorrelation of
r = 0.225.
The reason that the present genetic study is useful is that phenotypical correlations can only show that a relationship exists, but they do not provide information about which factors contribute to the correlations. Behavioral genetic analyses with twin data, however, allow a distinction between genetic and environmental factors contributing to associations (Plomin et al.,
2008). Such analyses are based on the fact that monozygotic twins share approximately 100% of their genetic variance, whereas dizygotic twins share, on average, 50% of their genes. Behavior genetics assumes that monozygotic twins, reared together, do not share more etiological environmental events than dizygotic twins, reared together (Kendler et al.,
1993). Therefore, differences in the extent to which monozygotic and dizygotic twins resemble each other are attributed to the effects of genes (i.e., heritability). With behavioral genetic analyses, a phenotypical correlation can be decomposed into additive genetic effects (A), non-additive genetic effects (D), shared environment (C), and non-shared environment (E). The difference between additive and non-additive genetic effects is that in the former multiple genes are assumed to independently contribute to a trait (or correlation between traits). Non-additive genetic effects, on the other hand, imply dominance and/or polygenetic effects (e.g., interactions between genes).
With regard to vocational interests, it is informative to distinguish between environmental and genetic influences on the relationship with personality. If there is a relevant heritable component then this would indicate that genes that influence individual differences in personality, i.e., the GFP, are also involved in individual differences in vocational interests.
Method
Sample
Participants in study 3 were the 768 adolescent twin pairs (1536 individuals) in the National Merit Twin Study. A full description of the procedures and tests are given by Loehlin and Nichols (
1976). The twins were identified among the high school students who took the national merit scholarship qualifying test (NMSQT) in the USA in 1962. The monozygotic (
N = 509) and dizygotic (
N = 330) pairs were selected out of the roughly 60,000 high school juniors who completed the NMSQT. Using a large 1082-item questionnaire, the study assessed a wide range of variables, including personality and vocational interests, which were the main focus of the present research. The participants were in the eleventh grade at the time of testing. All twin pairs were of the same sex, with 58.2% being female and 41.8% male.
Results
The general factor in the CPI of the National Merit Dataset has already been extensively shown in other studies. Therefore, it would not be useful to present the same analyses again here. Rushton and Irwing (
2011) used CFA/SEM to show that in the specific CPI scales in this dataset, six intermediate higher-order factors can be identified, which are subsumed by the two higher-order factors stability and plasticity (see also study 1). The GFP was the highest-order factor loading on stability and plasticity. The model (see Fig. 3 on p. 562, of Rushton & Irwing,
2011) showed a good fit according to a range of indices. In a later study, Loehlin also extracted the GFP from the same dataset by means of taking the first unrotated factor from principal axis factoring. For reasons of comparison, he extracted GFPs from the CPI scales, from CPI facets, and also directly from the items, only to find that the general factors with the different methods correlated in the range
r = 0.92 to 0.99. The above pattern of findings confirms that the GFP is robust with respect to extraction method. Accordingly, in the present study, we used the same method as Loehlin (
2011) to extract the GFP as the first unrotated factor using PAF. The general factor explained around 34% of the variance in the underlying subscales. The GFP factor loadings on the scales were in accordance with expectations and ranged from 0.18 (flexibility) to 0.85 (tolerance). See also, Loehlin (
2011) and Dunkel et al. (
2014) for further information on the GFP and its specific factor loadings in this sample. Each participants’ score on the GFP is calculated with the regression method which is the sum of products from their standardized score on each specific CPI scale and its corresponding factor loading.
Personality and Vocational Interests
The zero-order correlations between the study’s variables separately for twins 1 and 2 (the labeling of participants as either twin 1 or twin 2 was random) are displayed in Table
9. The table shows that, although the correlations between the personality and interests were modest overall, the GFP was only significantly correlated with social and investigative interests. Different from the previous two studies was that, for twin 1 as well as twin 2, the GFP did not show a significant correlation with enterprising interests.
Table 9
Zero-order correlations between the variables, separately for twin 1 (above the diagonal) and twin 2 (below the diagonal)
1. Sex | - | − 0.13* | 0.02 | − 0.29** | − 0.07 | 0.22** | 0.40** | − 0.13* | − 0.10* | 0.10* |
2. Cognitive ability | − 0.15** | - | 0.33** | − 0.11** | 0.13** | 0.10** | − 0.04 | − 0.03 | − 0.10* | − 0.07 |
3. GFP | − 0.01 | 0.36** | - | − 0.03 | 0.19** | 0.09 | 0.10** | 0.04 | − 0.05 | 0.05 |
4. Realistic | − 0.23** | 0.01 | − 0.04 | - | 0.29** | 0.06 | 0.04 | 0.26** | 0.28** | 0.45** |
5. Investigative | − 0.09 | 0.16** | 0.22** | 0.27** | - | 0.22** | 0.12* | 0.09 | 0.05 | 0.35** |
6. Artistic | 0.18** | 0.19** | 0.09 | 0.04 | 0.15** | - | 0.39** | 0.24** | 0.05 | 0.57** |
7. Social | 0.33** | − 0.07 | 0.16** | 0.00 | 0.11* | 0.30** | - | 0.30** | 0.16** | 0.62** |
8. Enterprising | − 0.16** | 0.01 | 0.04 | 0.26** | 0.05 | 0.26** | 0.29** | - | 0.47** | 0.79** |
9. Conventional | − 0.10* | − 0.04 | 0.01 | 0.31** | 0.02 | 0.01 | 0.18** | 0.47** | - | 0.67** |
10. Profile elevation | − 0.07 | 0.01 | 0.13* | 0.44** | 0.08 | 0.35** | 0.44** | 0.93** | 0.72** | - |
In this dataset, there were also significant correlations again between gender and cognitive ability, on the one hand, and vocational interests, on the other hand (see Table
9). Based on a similar line of reasoning as in studies 1 and 2, we, therefore, considered it informative to also report the findings after controlling for these two variables. The partial correlations are reported in Table
10 and show that inclusion of the control variables did not change the pattern of findings or conclusions, because investigative and social were still the only two vocational interests that significantly related to the GFP.
Table 10
Partial correlations (controlling for sex and general cognitive ability) between vocational interests and the GFP, separately for twin 1 and twin 2
Realistic | − 0.03 | 0.03 |
Investigative | 0.17** | 0.16** |
Artistic | 0.01 | 0.05 |
Social | 0.19** | 0.11** |
Enterprising | 0.05 | 0.07 |
Conventional | 0.03 | − 0.01 |
Profile elevation | 0.13* | 0.07 |
As a next step, we estimated the heritability of the GFP and the vocational interests based on the phenotypical resemblance between monozygotic (MZ) and dizygotic (DZ) twins (see Table
11). Because the MZ correlations were not > 2 times the value of the DZ correlations (see Table
11), we tested the ACE model instead of the ADE model. For all relevant variables, using Cholesky decomposition, we estimated the additive genetic variance (A), the level of variance attributed to the shared environment (C), and the variance component that includes unique environmental variance as well as measurement error (E) (ACE vs saturated:
χ2 (15) = 12.17,
p = 0.76). For each of the variables tested, it was clear that there was no variance attributed to the shared environment (e.g., parenting style, SES). Accordingly, running AE models confirmed that the C component could be dropped without significant changes in the model fits (AE vs ACE:
χ2 (3) = 3.19,
p = 0.36).
Table 11
Correlations (for MZ and DZ) and proportion of phenotypic variance due to additive genetic (A), shared environmental (C), and unique environmental and measurement error (E) variance
GFP | 0.58 | 0.38 | 0.60 (0.54–0.65) | 0 | 0.40 (0.35–0.46) |
Realistic | 0.30 | 0.28 | 0.22 (0.12–0.31) | 0 | 0.78 (0.68–0.88) |
Investigative | 0.35 | 0.20 | 0.36 (0.27–0.44) | 0 | 0.64 (0.56–0.73) |
Artistic | 0.33 | 0.28 | 0.33 (0.24–0.41) | 0 | 0.67 (0.59–0.76) |
Social | 0.47 | 0.26 | 0.39 (0.32–0.46) | 0 | 0.61 (0.54–0.68) |
Enterprising | 0.33 | 0.14 | 0.30 (0.21–0.37) | 0 | 0.70 (0.62–0.79) |
Conventional | 0.24 | 0.12 | 0.22 (0.12–0.32) | 0 | 0.78 (0.68–0.88) |
Profile elevation | 0.20 | 0.38 | 0.27 (0.06–0.44) | 0 | 0.73 (0.55–0.95) |
In general, from Table
11, it can be derived that, as reported in previous studies, the GFP showed a substantial heritable component of 60%. The heritability of the vocational interest dimensions ranged from 22% for realistic and conventional to 39% for social interests.
As social and investigative interests were the only two dimensions that showed significant phenotypical correlations, we tested their genetic correlations with the GFP. The genetic correlation between the GFP and social interest was r = 0.31 (confidence interval [CI] = 0.19; 0.42) and significant at p < 0.05. The correlation between the unique environmental components was low r = − 0.01 (CI = − 0.09; 0.08) and non-significant. The genetic correlation between the GFP and investigative interests was r = 0.37 (CI = 0.23; 0.50) and also reached significance. The unique environmental correlation was low r = 0.09 (CI = − 0.01; 0.19) and not significant.
Discussion
Using the National Merit sample, we replicated the finding from study 1 and study 2 that the GFP is related to vocational interests with a social component. Study 3 complemented the previous two studies by showing that the GFP and social interest were also significantly related at the genetic level, thereby providing insight into the etiology of the relationship.
Two findings in study 3 were not entirely in line with studies 1 and 2. The most salient one is the non-significant relation between the GFP and enterprising interests. The other difference was the significant GFP–investigative interest link. Although, we cannot provide conclusive answers to what may have caused those differences, one plausible explanation is the nature of the sample. In contrast to the previous samples in studies 1 and 2, the National Merit sample consists only of students who scored very high on the initial scholastic aptitude tests (Loehlin & Nichols,
1976). Individuals with high cognitive ability (e.g., National Merit Students) express stronger interest in investigative occupations (Pässler et al.,
2015). Moreover, in the RIASEC model of vocational interests, investigative and enterprising interests are considered opposing dimensions (Holland,
1997). Thus, compared to the population, participants in the National Merit sample may, on average, have had a lower interest in enterprising (and a higher interest in investigative interests) in the first place. This possibly might have distorted the GFP–enterprising interest relation. Despite these variations in findings, however, study 3 was consistent with the previous two studies in showing a GFP–social interest relationship.
The fact that the GFP–vocational interest relationship showed a relevant heritable component supports the notion that the genes that provide people with a disposition for a higher GFP are probably partially the same genes that push a person towards interest in social (and in this case also investigative) interests. As such, study 3 goes beyond the two previous studies by indicating that a part of the personality–vocational interest relationships is at a rather fundamental level.
The dataset of twins from the National Merit sample had the advantage that we could conduct behavioral genetic analyses. Yet, the sample had a limitation that it was not representative for the population, but consisted of those with very high scores on scholastic aptitude tests. Subsequently, in future research, it would be useful to test the genetic correlation between the GFP and vocational interest again in other, more representative samples.
General Discussion
In the present set of studies, we examined preferences for occupations and activities by taking into account the GFP. This approach may contribute to the literature in several ways. First, the studies provide information about the nature of the GFP, which is relevant for the more fundamental scientific discussion on the hierarchical structure of personality. Second, the set of studies provide a novel perspective on how personality and vocational interests are related by assuming that the shared variance among personality dimensions should not be simply dismissed (as in previous studies using linear regression analyses) but has explanatory power.
With regard to the former point, across the four samples, a general pattern of findings emerged, indicating that the GFP particularly relates to interest in working with people. This entailed that social and enterprising interests showed the strongest relations with the GFP (studies 1 and 3) and with the broad interest factor of working with people (study 2). The GFP showed consistent and significant phenotypical as well as genetic correlations with social interests.
This pattern of findings partly supports the notion that the GFP is a broad social effectiveness factor. Humans are social by nature, and it is, therefore, clear that getting along with others at work or using social interactions to succeed are common themes in most occupations (Wolfe et al.,
1986). Yet, as jobs differ in the extent to which their success and satisfaction depend on such social components, it is reasonable to assume that those people who are more socially effective tend to gravitate toward more socially laden jobs or activities. This assumption was already supported by previous studies on the relationship between emotional intelligence and vocational interests (e.g., Schermer et al.,
2015) and, in the present research, has also been extended to the GFP.
The most obvious alternative explanation, namely that the GFP is merely a statistical artifact, method bias, or social desirability factor (Ashton et al.,
2009; Bäckström et al.,
2009; Connelly & Chang,
2016) cannot be completely ruled out by the present findings, but may nevertheless be considered substantially less likely for the following reasons. First, it does not seem obvious that response bias or social desirability would particularly strongly relate to social occupations. Certain jobs, such as engineer, computer programmer, and rocket scientist, generally have a high status, even though they are not particularly social. Second, if the scores on personality would be strongly influenced by response biases, then it can be logically assumed that such biases remain rather consistent over different measures. The GFP, however, did not strongly correlate with the general factor of vocational interests (profile elevation), which, at least, indicates that they were not prone to similar types of response biases. This finding, in itself, again does not rule out the possibility that one of the general factors is influenced by response bias, but it makes it nevertheless, somewhat less likely, particularly, in the broader context of findings. Third, the relations between the GFP and social interests were found at the genetic level. Although even this latter finding does not fully exclude the possibility of social desirability or response bias (both can also have a genetic component), it does suggest that the GFP–social interest link may be relatively deeply ingrained and have trait-like properties.
Beyond contributing to insight into the nature of the GFP, the present findings also generally encourage a new way of looking at the relationship between personality and vocational interest. In previous research, it has often been assumed that personality dimensions are fundamentally independent of each other, and this assumption has theoretical and methodological implications. Assuming independent traits implies, for example, that one has to establish different — unique — explanations for each relationship between a specific personality dimension and vocational interests (e.g., Larson et al.,
2002; Mount et al,
2005). This is not a parsimonious approach.
Two questions that may arise in this context are (1) whether the GFP can provide a unique contribution to explaining vocational interests beyond the specific personality dimensions (e.g., the Big Five), and (2) whether the GFP findings can be explained by the effects of one or two specific traits, such as extraversion and neuroticism.
Regarding the former question, from the perspective of a substantive general factor, a test of its influence beyond lower-order traits such as the Big Five would not be meaningful. After all, the GFP is assumed to be partially present in each of the specific personality dimensions (Van der Linden et al.,
2016). Therefore, controlling for Big Five would mean deleting the true variance of the general factor. One can compare this to testing whether a general factor of cognitive ability (
g) contributes beyond the sub-tests from which it is extracted. This would not make much sense (Jensen,
1998). Doing it the other way around, however, by testing whether the unique variance of specific traits contributes, beyond their shared component, is very informative. In these tests that we conducted in studies 1 and 2, it became clear that the GFP accounts for the lion’s share of the relationships between specific personality dimensions and vocational interests. The GFP explained relatively large proportions of the variance in vocational interests with strong social components. The combined unique variances of the mores specific traits often explained less additional variance than the GFP. The comparisons between the GFP and the unique components of traits confirm that the notion of a general factor does not imply that lower-order traits become obsolete. Specific traits may sometimes be better suited to capture individual differences. In line with this, the analyses in studies 1 and 2 show that, in some cases, the unique trait variance can add explained variance beyond the GFP. Yet, if one would ignore the GFP or is unaware of its existence, then one neglects a relevant “part of the picture” when trying to explain what may cause the associations between personality and vocational interests.
Regarding the second question, as the GFP, by definition, reflects the shared variance of the underlying traits, it can never be “just” extraversion or neuroticism (or any other specific trait). This can be confirmed, for example, by looking at the factor loadings of the samples in study 1. Those reveal that the GFP is not based on the influence of (a combination of) one or two traits, but rather represents a balanced mix of socially desirable or socially effective traits.
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