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Biological Aspects of General Factor of Personality
CHAPTER 6
Biological Aspects of General Factor of Personality EVOLUTIONARY BASIS OF THE GENERAL FACTOR OF PERSONALITY The origins and development of personality are embedded into the evolution of the human species. The General Factor of Personality (GFP) in its substantial form (see Chapter 4) is not an exception. The evolution can be defined as a process of changing heritable features of living organisms over generations, which implies the characteristics of species, individual organisms, and genes. The main difference between classic Darwinian and modern (sometimes labeled neo-Darwinian) theory of evolution concerns the units of evolutionary processes. The classic Darwinian theory of evolution is focused on species and individual organisms, while the modern theories of evolution are focused on the molecular level of evolution including the genes. Nevertheless, the human characteristics including the personality are the subject of both classic and modern theory of evolution. Theory of evolution is still the leading conceptual framework for investigating all biological aspects of the human personality. In the literature, we can find a great number of studies devoted to the biology of personality (for a review, see Figueredo, Jacobs, Burger, Gladden, & Olderbak, 2011; Figueredo, Woodley of Menie, & Jake Jacobs, 2016; Yarkoni, 2015). These studies include the research of the evolutionary aspects of personality (Buss, 1991, 1997, pp. 317–344; Figueredo et al., 2016), behavioral genetics of personality (Bouchard & McGue, 2003; Harris, 2006; Loehlin, McCrae, Costa, & John, 1998), neuroanatomy of personality (Depue & Collins, 1999; DeYoung, Peterson, & Higgins, 2001, 2005; Figueredo et al., 2011, pp. 378– 381), and neurophysiology and neurochemistry of personality (Depue & Collins, 1999; Figueredo et al., 2011, pp. 381–385). In this chapter, we will focus on the biological basis of the GFP, especially on the evolutionary, genetic, and neuroscientific aspects. The General Factor of Personality ISBN 978-0-12-811209-0 http://dx.doi.org/10.1016/B978-0-12-811209-0.00006-6
© 2017 Elsevier Inc. All rights reserved.
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EVOLUTIONARY STRATEGIES AND PERSONALITY The evolutionary “logic” behind the emergence of the GFP was nicely explained by Rushton, Bons, and Hur (2008, p. 1175): “The position to be presented here grows directly out of Darwin’s (1871) view that natural selection endowed modern humans with larger brains, increased levels of general and social intelligence, and a more ethical and prosocial personality than ’primeval man and his ape-like progenitors’ (p. 159). Darwin wrote of increased levels of human qualities such as ’courage, sympathy, and faithfulness,’ and a ’need for approval by others,’ with a concomitant decrease in the frequency of ’selfish and contentious people’ who ’will not cohere, and without coherence nothing can be effected’ (p. 159). Darwin described how moral and inter-personal skills go hand in hand with the greater intelligence modern people possess.” According to the evolutionary psychological perspective, we may reasonably expect that the Big Five should correlate in concordance with the evolutionary pressures in favor of adaptive function of each dimension. Thus, the Big Five correlations will form a stable pattern consisting of mutual positive correlations between Extraversion, Openness, Agreeableness, and Conscientiousness and negative correlations of these traits with Neuroticism. Consequently, we may also expect the positive manifold in correlation matrix of the Big Five, provided the reversal of Neuroticism to the Emotional Stability. And that is exactly the same correlation pattern being reported in the studies of GFP (Musek, 2007; Rushton & Irwing, 2008, 2009; Rushton et al., 2009). The question arises therefrom, which special model of evolution processes can be most efficiently applied to the emergence of the GFP? Two mutually connected theoretical approaches can be derived from the abovementioned Darwinian conceptual frame: the differential K theory and life history model. Both describe the evolutionary strategy, which supposes the coevolution of different personality traits being oriented toward the social benefits in human species.
DIFFERENTIAL K THEORY According to Wilson (1975), two opposed reproductive strategies can be traced in evolution: one producing a large number of fast-growing offspring with minimal parental care (r-strategy) and, a second, producing a small number of offspring with prolonged parental care and rearing (K-strategy). The organisms with r-strategy are smaller, short-lived, live in less stable and predictable environments, have a high-level of fecundity, and invest very little in the offspring. On the other hand, the organisms with K-strategy live
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Table 6.1 Typical differences in characteristics of r- and K-reproductive strategy Characteristic r-Organisms K-Organisms
Longevity Energy Intelligence Litters Reproduction Maturation Progeny Care of offspring Sex drive Birth size Social life Representative species
Short-lived Small Weak Wasting energy Low Large Early age Fast Quantity Little Strong Small Nonsocial Small rodents Salmons Insects Bacteria
Long-lived Big Strong Efficient energy handling High Small Late age Slow Quality Great Weak Large Social Humans Elephants Whales Arctic terns
longer, live in more stable and predictable environments, produce only a few progeny, and invest much more time and energy in them (see Table 6.1). Obviously, human beings occupy the very extreme on the K-strategy. Rushton et al. (2008, p. 1173) summarized the basic platform of differential K theory in the following formulation: “Twenty years ago, Rushton (1985, 1990) conjectured that ’one basic dimension—K—underlies much of the field of personality’ (1985, p. 445). He proposed that human social behavior is best understood as being part of a life-history—a suite of traits genetically organized to meet the trials of life—survival, growth, and reproduction. Building on Wilson (1975) theory of r-K reproductive strategies, which explains how animals colonize islands and reach population equilibrium, Rushton postulated that diverse personality traits covaried with altruism, intelligence, attachment styles, reproductive strategies, growth, longevity, and fecundity. Animals can adopt either of two strategies: produce a large number of fast maturing offspring but devote little parental care to ensure their survival (the r-strategy), or invest in a few slower-maturing, high quality offspring and devote considerable parental care to rearing them and ensuring that a much larger proportion survives (the K-strategy). Rushton dubbed his proposal ’Differential K Theory’ in order to emphasize that all humans were at the K-end of the continuum when compared against other species.”
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In this context, the introduction of the GFP (Musek, 2007) can be conceived as a confirmation of the general personality dimension, which was anticipated by Differential K Theory and corroborated also in the research in the line of the life history model (Figueredo, Vásquez, Brumbach, & Schneider, 2004, 2007; Figueredo et al., 2005, 2016). Indeed, the GFP is very substantially connected with different measures of prosocial orientation and social effectiveness (see Chapter 5) and represents a part of even more general Super-g factor, which embraces almost the entire domain of noncognitive traits (see Chapter 8). In this respect, the GFP can be easily compared and identified with the personality factor discovered by Figueredo et al. (2007).
LIFE HISTORY MODEL The evolution of personality including the GFP can be thus saliently explained in terms of Differential K Theory, which is further a part of the broader theoretical model labeled the “life history theory” (McArthur & Wilson, 1967; Wilson, 1975). Life history theory is focused on the differences in the allocation of energy and material resources in the adaptation to environment. Different species and also individual organisms vary between the orientation toward efficient mating and production of offspring (mating effort and reproductive effort) and orientation toward efficient survival of individual organism and offspring (somatic effort and parental effort). Organisms with r-reproductive strategy (see previous discussion) typically exhibit mating and reproductive effort, while organisms with K-reproductive strategy including humans manifest somatic and parental effort. In the excellent introduction into the evolutionary aspects of personality and GFP, Figueredo et al. (2016, p. 949) formulated the basic theoretical position as follows: “Evolutionary models of personality, such as those based in life history theory, have gone further by integrating the GFP into a broader life history super-factor termed Super-K, which encompasses behavioral manifestations of life history strategy and global measures of physical and mental health (this being the aforementioned covitality factor…). The life history model posits that the high-functioning pole of GFP relates to prosocial or altruistic orientations necessary for optimum fitness under conditions of low extrinsic mortality and morbidity where organisms exist at the carrying capacity of their environment and conspecific densities are high (Figueredo & Rushton, 2009).”
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The research in biology and psychology confirmed many hypotheses derived from life history theory and Differential K Theory (see an extensive review in Figueredo et al., 2016). The traits that can be connected with the K-reproductive strategy correlate and GFP represents a crucial dimension, which explains a lot of the shared variance in these traits (Figuredo et al., 2016, pp. 952–956). There is convincing evidence that variables of parental behavior and parenting style correlate with the well-being of children (Ellis, 2004). Figueredo et al. (2007) extracted a common factor underlying a variety of variables representing K-reproductive strategy or slow life history strategy in the large set of MIDUS I scales (Brim et al., 2000). The common slow life history factor (labeled the expanded K-factor) saturated variables like mother relationship quality, father relationship quality, marital relationship quality, children relationship quality, family support, altruism toward kin, friends’ close relationship quality, communitarian beliefs, religiosity, financial status, health control, agency, advice seeking, foresight/anticipation, insight into past, primary control/persistence, flexible/positive reappraisal, and self-directedness/planning (Figueredo et al., 2007, pp. 397–398). The expanded K-factor strongly correlated with the GFP (r = .66). In Chapter 8 we will report the results of the analysis of a large set of 32 MIDUS II variables (Ryff et al., 2007) where a very general common dimension was found (Comprehensive Factor of Personality or CFP), which also strongly correlates with the GFP (r = .70). If the analyses include the larger set of 63 variables, another general factor labeled Super-g was found. Super-g substantially correlated with the CFP (r = .49) and modestly with the GFP (r = .25), although the larger set includes the variables, which are not so closely related than 32 variables in first set. In the larger set we can find several variables that are not characteristic for the slow life history strategy.
GENETICS The mechanisms of evolution imply genetic effects on the involved characteristics. Personality dimensions are thus genetically shaped and heritable including the Big Five. In a large meta-analysis on the heritability of human traits, Polderman et al. (2015) reported 49% of heritable variance across 17,804 traits from 2748 publications including 14,558,903 twin pairs. Some (but not all) physical characteristics and cognitive abilities including
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intelligence have very high genetic components, while the heritability of values, attitudes, and beliefs is by the rule lower although often significant and even substantial (Eaves et al., 1999; Ludeke, Johnson, & Bouchard, 2013; Olson, Vernon, Jang, & Harris, 2001). According to Harris (2006), about 45% of the variance in personality is genetic, very little is accounted for by shared environment, and up to 55% to nonshared environment. It is therefore no mystery that the GFP, which accounts for the shared Big Five variance, is heritable too. In twin studies, the heritability of the Big Five was convincingly detected. According to these studies, the percent of the heritable variance in the Big Five is between 40 and 60 (Bouchard & McGue, 2003; Jang, Livesley, & Vernon, 1996; Jang et al., 2001; Loehlin et al., 1998; Vernon, Martin, Schermer, & Mackie, 2008). More detailed, the percent of genetic variation for “Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness was estimated at 41%, 53%, 61%, 41%, and 44%, respectively” (Jang et al., 1996, p. 577). However, the heritability measures yielded lower genetic influence in some studies, where the approaches other than twin research were applied. Power and Pluess (2015) found significant heritability only for Neuroticism and Openness and not Extraversion, Agreeableness, and Conscientiousness in a study using the Genomicrelatedness-matrix Residual Maximum Likelihood (GREML) analysis approach to genetic research. Yet, the heritability of extraversion was confirmed in another study using GREML (Vinkhuyzen et al., 2012). In the study, inaugurating the concept of the GFP (Musek, 2007), the heritability of the GFP was assumed but not directly measured. Very soon, Rushton et al. (2008) performed heritability analyses for 174 pairs of MZ twins and the 148 pairs of DZ twins on the GFP extracted from 29 self-rating scales. In regard to the heritability of the GFP, the authors claimed, “For the GFP itself, calculated using factor scores, the MZr = .55 and the DZr = .14, indicating evidence of genetic dominance and a heritability of 82%. Factor analyses performed on the genetic variance– covariance matrices (the G matrix) found a higher-order genetic GFP, which accounted for 32% of the genetic variance among the Big Five lower-order factors. (Going directly from the lower order traits to the Big One accounted for 28% of the genetic variance among those traits.)” (Rushton et al., 2008, p. 1179). Other twin studies also demonstrated considerable heritability of the GFP.Veselka, Schermer, Petrides, and Vernon (2009) conducted two studies, where the GFP was extracted from different personality scales. In both
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studies, the individual differences in the GFP were fully accounted for by genetic and nonshared environmental factors. Loehlin and Martin (2011) examined several thousand Australian twin pairs and confirmed the heritability of the GFP. The authors also demonstrated dominance effects of GFP, which were probably due to the dominance of the scales constituting the GFP. In the analysis of the MIDUS Twin sample, Figueredo et al. (2004, 2007; see also Figueredo & Rushton, 2009) compared the genetic correlations of three complex factors that were found across a large set of variables in the MIDUS survey data (Brim et al., 2000). The higher-order GFP correlated with the expanded K-factor (r = .66) and with the covitality factor (r = .36). All three factors have a very substantial genetic component, the GFP (h2 = .59), K-factor (h2 = .65), and covitality factor (h2 = .52). The genetic correlations between all three factors based on a large scale of traits suggest the integration of the several genetically regulated behavioral elements into a consistent reproductive strategy (Figueredo et al., 2011). Therefore, the authors deduced two important conclusions: “First, the genetic correlations among traits within each multivariate construct suggest that the higherorder levels of aggregation proposed as having merely heuristic utility may be neither intellectual conveniences nor statistical artifacts, but instead reflect a genuine functional integration of adaptive traits at the genetic level. Second, the genetic correlations among the higher-order constructs (the K-factor and the GFP) suggest that a correct application of Brunswik Symmetry identifies the level of biological organization at which the aggregates are functionally linked” (Figueredo et al., 2011, p. 398). Reanalyzing the data from MIDUS twin sample, Figueredo and Rushton (2009) found further evidence for the nonadditive effects in the genetic covariance between the GFP, general health factor, and life history factor. The authors summarized the evidence for shared genetic dominance among three factors as follows: “We suggest these genetic correlations support the view that a slow (K-selected) life history strategy, good health and the GFP coevolved and are mutually coadapted through directional selection” (Figueredo & Rushton, 2009, p. 555).
GFP IN THE LIGHT OF NEUROSCIENCE Neural Correlates of Personality Personality traits have been often examined by means of neuroscientific approaches including the research of neurological, neurophysiological, and
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neurochemical effects. For example, all Big Five dimensions have been extensively investigated in connection to the cortical and subcortical brain functioning including the functions of basic neural structures and their associations (Rodrigo et al., 2015). The connections of personality traits to the neurotransmitter systems with the respective neurophysiological and neurochemical aspects have been also investigated in many studies (Depue & Collins, 1999). However, the neuroscientific aspects of personality are very complex and far from being thoroughly investigated. With regard to the GFP, we should therefore focus on efficient strategy in order to identify possible neuroscientific correlates. A promising strategy may be in trying to find the answers to the question, which neuroscientific factors must be considered to explain the functional coordination of high emotional stability (low neuroticism), extraversion, conscientiousness, agreeableness, and openness versus the opposite. Pure logic implies that this combination of the Big Five, which is typical for the GFP, may at the personality level represent socially acceptable and desirable control of our behavior, emotions, and thoughts (e.g., inhibitory control). The inhibitory control can be defined as the ability to control our behavior, emotions, and cognitions in order to adapt to our natural and social environment (Cahn-Weiner, Malloy, Boyle, Marran, & Salloway, 2000; Hasher, Zacks, & May, 1999; Rodrigo et al., 2015; Verbruggen & Logan, 2008). The inhibitory control is thus necessary for socially adequate behavior, which is associated with personality traits including the GPF.
Inhibitory Control and Prefrontal Cortex Musek (2007) already speculated that the correlations among the Big Five, which underlie the GFP, might be connected to the neural mechanisms that influence the activity of two great neurophysiological systems, the serotonergic and dopaminergic system, respectively. Both systems are important in relation to inhibitory control, especially the combination of increased dopaminergic and suppressed serotonergic neural activation. According to the author (p. 1228), the GFP could be linked to the “biological mechanism combining low levels of the functioning of the central serotonergic system (Spoont, 1992;Tork, 1990) and higher levels of the functioning of ascending rostral dopaminergic system (Ashby, Isen, & Turken, 1999; Davidson, 1995, pp. 361–387; Depue & Collins, 1999; Panksepp, 1999; Pauls, Wacker, & Crost, 2005). This combination has been implicated in the higher values of Stability and Plasticity factors (DeYoung et al., 2001) that, according to the present results, constitute the Big One. Given the heritability of the Big
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Five, it is possible that speculated covariation of dopaminergic and serotonergic system is genetically mediated.” Yet, which neural mechanism could be responsible for raising the emotional stability (lowering neuroticism), conscientiousness, agreeableness, extraversion, and openness? Exactly this question was posed by Rushton et al. (2008, p. 1181): “What neurological substrates might evolution lay down to increase the GFP and improve inter-personal efficiency? One straightforward possibility is adding neural tracts in the frontal cortex, which is responsible for self-control and forward planning. A large body of evidence now supports the ’social brain-social complexity’ hypothesis. For example, across species of primates, there is a strong positive correlation between the size of the neocortex (relative to body size) and the larger the group size, which is a function of how many individuals in a group can be recognized and how much information can be processed… It has been well known since the famous case of Phineas T. Gage that damage to the frontal cortex, reduces conscientiousness and disinhibits aggressive, impulsive, and anti-social behavior…, and also lowers fluid intelligence and judgment…” The prefrontal cortex is almost certainly involved in the processes of inhibitory control, although the activation of other cortical regions and structures has also been observed (see the meta-analysis of 47 functional magnetic resonance imaging (fMRI) studies by Swick, Ashley, & Turken, 2011). It seems that the prefrontal cortex, especially the right inferior frontal gyrus, are the structures that are of the utmost importance in the functioning of the inhibitory control (Aron, Robbins, & Poldrack, 2004; Chikazoe, Konishi, Asari, Jimura, & Miyashita, 2007). Unfortunately, there is very little research examining the connections between the Big Five and functional activation of the prefrontal cortical structures. However, the few studies that are relevant in this respect strongly indicated the role of the prefrontal activation in the GFP. These studies used a rather recent methodology, fMRI and near-infrared spectroscopy(fNIRS) in functional detection of neural personality correlates (Eisenberger, Lieberman, & Satpute, 2005; Forbes et al., 2014; Rodrigo et al., 2015; Sosic-Vasic, Ulrich, Ruchsow, Vasic, & Gron, 2012). Using fNIRS, Rodrigo et al. (2015) discovered that greater activation of lateral region of the prefrontal cortex was associated with higher levels of extraversion, agreeableness, and consciousness and with lower levels of neuroticism. This is exactly the pattern of the Big Five that is typical for the high level of GFP. The authors (p. 1) concluded that “these results suggest that personality traits reflecting greater emotional stability, extraversion, agreeableness and conscientiousness may be associated with more efficient recruitment of control
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processes subserved by lateral regions of the prefrontal cortex.” Why we can be so certain that the detected pattern of personality–prefrontal cortex relation should reflect the GFP? It is so because we can exclude the possibility that the Big Five in the study of Rodrigo et al. (2015) do not correlate and therefore do not constitute the GFP. Instead, the Big Five correlated in the manner typical for the GFP (p. 4).The authors did not calculate the GFP, but if we reexamine the reported Big Five correlations, the GFP clearly emerges saturating neuroticism (−.64), extraversion (.58), agreeableness (.40), conscientiousness (.37), and openness (.17). If the GFP would be calculated, its connections to the activation of the prefrontal cortex would be greater than those of any single Big Five dimension. Relative activation of the prefrontal cortex can be indicated also by measuring the respective asymmetries in allocated brain functions. Thus, the frontal left to right alpha asymmetry can serve as an index of the prefrontal activity. According to Sutton and Davidson (1997), higher left resting prefrontal activity is associated with the behavioral activation system (BAS) and higher right prefrontal activation with the behavioral inhibitory system (BIS), and similar although less clear difference in relative prefrontal activity was observed for the positive and negative affect (Figueredo et al., 2011, pp. 397–380). These findings can be indirectly connected with the GFP, which is related to BAS-BIS systems and affect. The GFP correlates positively with BAS and positive affect and negatively with BIS and negative affect. Thus, if the inhibitory control is associated with the greater left prefrontal cortical activation, we can hypothesize that higher GFP would be connected with the greater frontal alpha asymmetry in EEG. Uibo, Allik, and Hiettanen (2012) discovered that extraverted and emotionally stable persons exhibit greater positive frontal alpha asymmetry (more activation in the right side) in gaze direction behavior. The greater activation of frontal over posterior regions was found in extraverted, emotionally stable, and conscientious individuals. These results, which may be indicative also for the differences in GFP, indicate the role of the frontal region in approach versus avoidant behavior (the former being characteristic for higher GFP). More direct connection of the EEG alpha asymmetries and GFP can be obtained by analyzing the MIDUS II neurological data (Ryff & Davidson, 2010, p. v1). According to our very robust analyses, the GFP significantly correlates with C3/C4 alpha asymmetry (r = .19), maybe reflecting the brain activities associating frontal and central cortical regions (Musek, 2016). Yet, caveat! The associations between the GFP and prefrontal activation do not mean that the personality is not involved into the functioning of
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other different cortical structures and their associations. Personality traits very probably have extremely complex connections to numerous brain functions, associations, and structurations, which are not yet satisfactorily investigated (Figueredo et al., 2011; Yarkoni, 2015). However, the relations of the GFP to the inhibitory control and prefrontal activation should be very informative for the biological understanding of the personality.
Affect, Amygdala and Limbic System The GFP may be linked with still other neural substrates, especially if we consider the connections of the GFP with other domains of psychological variables as affect, well-being, self-esteem, coping, mental health, etc. (see also Chapter 8). Personality dimensions are linked with affect: neuroticism with negative affect and extraversion with positive affect, while less extensive connections with both affects have been observed in other personality dimensions too (Steel, Schmidt, & Shultz, 2008). Yet, both dimensions of affect are also inherent in other different domains of noncognitive psychological variables, especially in well-being and mental health. Moreover, some biological bases of both affects have been reliably discovered. The role of amygdala in processing affect was known for a long time and was also recently clearly confirmed (Jin, Zelano, Gottfried, & Mohanty, 2015). According to the large meta-analysis of fMRI investigations, Lindquist, Satpute,Wager,Weber, and Barrett (2016) concluded that a set of limbic and paralimbic brain regions balance negative and positive affect. Thus, the research evidence has not confirmed the separate regulation of positive and negative affect so far. Recent research shows also that negative affect is more heritable than positive affect (Zheng, Plomin, & von Stumm, 2016). Thus, the limbic and paralimbic structures with their cortical associations also may be linked with the Big Five correlations and consequently with the GFP.
CONCLUSIONS From the theoretical point of view, the GFP can be postulated within the biological framework consisting of modern concepts of evolution, supported by genetic and neuroscientific evidence. Thus, the GFP can be cogently conceptualized within the solid frame of modern and even classic theory of evolution with all necessary genetic and neuroscientific apparatus. From the standpoint of the theory of evolution, the GFP should be interpreted in the context of the life history theory and Differential K Theory. Both predict the coevolution of personality traits,
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which are oriented toward the social benefits in human species. The evolutionary background of the GFP implies the genetic basis that should be realized through the functioning of the neural structures and associations that are involved in the processing of the Big Five correlations constituting GFP. The genetic research clearly proved the heritability of GFP and the neuroscientific research strongly suggests that GFP should be linked with the inhibitory control and the activation of prefrontal cortex and limbic structures. Thus, the theory of evolution represents a theoretical framework of the GFP construct. The evolutionary basis of the GFP is further corroborated by extensive genetic and neuroscientific research demonstrating the substantial heritability of the GFP and possible neurological, neurophysiological, and neurochemical factors connected with the GFP. The biological basis renders the GFP not only an empirically supported construct but also a construct that has a salient theoretical foundation.
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Ludeke, S., Johnson, W., & Bouchard, T. J. J. (2013). Obedience to traditional authority: a heritable factor underlying authoritarianism, conservatism and religiousness. Personality and Individual Differences, 55(4), 375–380. McArthur, R. H., & Wilson, E. O. (1967). The theory of island biogeography. Princeton, NJ: Princeton University Press. Musek, J. (2007). A general factor of personality: evidence for the Big One in the five-factor model. Journal of Research in Personality, 41, 1213–1233. Musek, J. (2016). General factor of personality and EEG brain asymmetries. Unpublished manuscript. Department of psychology. Ljubljana, Slovenia: University of Ljubljana. Olson, J. M., Vernon, P. A., Jang, K. L., & Harris, J. A. (2001). The heritability of attitudes: a study of twins. Journal of Personality and Social Psychology, 80(6), 845–860. Panksepp, J. (1999). Affective neuroscience. Oxford University Press. Pauls, C. A., Wacker, J., & Crost, N. W. (2005). The two components of social desirability and their relations to resting frontal brain asymmetry. Journal of Individual Differences, 26(1), 29–42. Polderman, T. J. C., Benyamin, B., de Leeuw, C. A., Sullivan, P. F., van Bochoven, A., et al. (2015). Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nature Genetics, 47, 702–709. Power, R. A., & Pluess, M. (2015). Heritability estimates of the Big Five personality traits based on common genetic variants. Translational Psychiatry, 5, e604. Rodrigo, A. H., Di Domenico, S. I., Graves, B., Jaeger, L., Ayaz, H., et al. (2015). Linking traitbased phenotypes to prefrontal cortex activation during inhibitory control. Social Cognitive and Affective Neuroscience, 1–11. Rushton, J. P. (1985). Differential K theory: the sociobiology of individual and group differences. Personality and Individual Differences, 6, 441–452. Rushton, J. P. (1990). Sir Francis Galton, epigenetic rules, genetic similarity theory, and human life history analysis. Journal of Personality, 58, 117–140. Rushton, J. P., Bons,T. A., Ando, J., Hur,Y.-M., Irwing, P.,Vernon, P. A., et al. (2009). A general factor of personality from multitrait-multimethod data and cross-national twins. Twin Research and Human Genetics, 12, 356–365. Rushton, J. P., Bons, T. A., & Hur, Y.-M. (2008). The genetics and evolution of the general factor of personality. Journal of Research in Personality, 42(5), 1173–1185. Rushton, J. P., & Irwing, P. (2008). A general factor of personality (GFP) from two metaanalyses of the big five: Digman (1997) and mount, Barrick, Scullen, and Rounds (2005). Personality and Individual Differences, 45, 679–683. Rushton, J. P., & Irwing, P. (2009). A general factor of personality in the Comrey personality scales, the Minnesota Multiphasic personality Inventory-2, and the Multicultural personality Questionnaire. Personality and Individual Differences, 46, 437–442. Ryff, C. D., Almeida, D. M., Ayanian, J. S., Carr, D. S., Cleary, P. D., Coe, C., et al. (2007). Midlife development in the United States (MIDUS II), 2004–2006. Documentations of scales in MIDUS II. [Computer file]. ICPSR04652-v1. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor]. http://dx.doi.org/10.3886/ ICPSR04652. Ryff, C. D., & Davidson, R. (2010). National survey of midlife development in the United States (MIDUS II): Neuroscience project. [Computer file]. ICPSR28683–v1. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor]. http://dx.doi.org/10.3886/ICPSR28683. Sosic-Vasic, Z., Ulrich, M., Ruchsow, M.,Vasic, N., & Gron, G. (2012).The modulating effect of personality traits on neural error monitoring: evidence from event-related FMRI. PLoS One, 7, e42930. Spoont, M. R. (1992). Modulatory role of serotonin in neural information processing, implications for human psychopathology. Psychological Bulletin, 112, 330–350.
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Steel, P., Schmidt, J., & Shultz, J. (2008). Refining the relationship between personality and subjective well-being. Psycholgoical Bulletin, 134, 138–161. Sutton, S. K., & Davidson, R. J. (1997). Prefrontal brain asymmetry: a biological substrate of the behavioral approach and inhibition systems. Psychological Science, 8(3), 204–210. Swick, D., Ashley,V., & Turken, U. (2011). Are the neural correlates of stopping and not going identical? Quantitative meta-analysis of two response inhibition tasks. Neuroimage, 56, 1655–1665. Tork, I. (1990). Anatomy of the serotonergic system. Annals of the New York Academy of Science, 600, 9–35. Uibo, H., Allik, J., & Hiettanen, J. (2012). How Big Five relates to electroencephalographic and behavioural correlates of eye contact. In 16th European Conference on Personality, Trieste, July 10–14, 2012. Verbruggen, F., & Logan, G. D. (2008). Response inhibition in the stop-signal paradigm. Trends in Cognitive Sciences, 12, 418–424. Vernon, P. A., Martin, R. A., Schermer, J. A., & Mackie, A. (2008). A behavioral genetic investigation of humor styles and their correlations with the Big-5 personality dimensions. Personality and Individual Differences, 44, 1116–1125. Veselka, L., Schermer, J. A., Petrides, K. V., & Vernon, P. A. (2009). Evidence for a heritable general factor of personality in two studies. Twin Research and Human Genetics, 12, 254–260. Vinkhuyzen, A. A., Pedersen, N. L.,Yang, J., Lee, S. H., Magnusson, P. K., Iacono, W. G., et al. (2012). Common SNPs explain some of the variation in the personality dimensions of neuroticism and extraversion. Translational Psychiatry [Electronic Resource], 2, e102. Wilson, E. O. (1975). Sociobiology:The new synthesis. Cambridge, MA: Harvard University. Yarkoni, T. (2015). Neurobiological substrates of personality: a critical overview. In M. Mikulincer, & P. R. Shaver (Eds.), APA handbook of personality and social psychology Personality processes and individual differences: Vol. 4. (pp. 61–84).Washington, DC:American Psychological Association. Zheng, Y., Plomin, R., & von Stumm, S. (2016). Heritability of intraindividual mean and variability of positive and negative affect: genetic analysis of daily affect ratings over a month. Psychological Science, 1–9. http://dx.doi.org/10.1177/0956797616669994.
Biological Aspects of General Factor of Personality EVOLUTIONARY BASIS OF THE GENERAL FACTOR OF PERSONALITY The origins and development of personality are embedded into the evolution of the human species. The General Factor of Personality (GFP) in its substantial form (see Chapter 4) is not an exception. The evolution can be defined as a process of changing heritable features of living organisms over generations, which implies the characteristics of species, individual organisms, and genes. The main difference between classic Darwinian and modern (sometimes labeled neo-Darwinian) theory of evolution concerns the units of evolutionary processes. The classic Darwinian theory of evolution is focused on species and individual organisms, while the modern theories of evolution are focused on the molecular level of evolution including the genes. Nevertheless, the human characteristics including the personality are the subject of both classic and modern theory of evolution. Theory of evolution is still the leading conceptual framework for investigating all biological aspects of the human personality. In the literature, we can find a great number of studies devoted to the biology of personality (for a review, see Figueredo, Jacobs, Burger, Gladden, & Olderbak, 2011; Figueredo, Woodley of Menie, & Jake Jacobs, 2016; Yarkoni, 2015). These studies include the research of the evolutionary aspects of personality (Buss, 1991, 1997, pp. 317–344; Figueredo et al., 2016), behavioral genetics of personality (Bouchard & McGue, 2003; Harris, 2006; Loehlin, McCrae, Costa, & John, 1998), neuroanatomy of personality (Depue & Collins, 1999; DeYoung, Peterson, & Higgins, 2001, 2005; Figueredo et al., 2011, pp. 378– 381), and neurophysiology and neurochemistry of personality (Depue & Collins, 1999; Figueredo et al., 2011, pp. 381–385). In this chapter, we will focus on the biological basis of the GFP, especially on the evolutionary, genetic, and neuroscientific aspects. The General Factor of Personality ISBN 978-0-12-811209-0 http://dx.doi.org/10.1016/B978-0-12-811209-0.00006-6
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EVOLUTIONARY STRATEGIES AND PERSONALITY The evolutionary “logic” behind the emergence of the GFP was nicely explained by Rushton, Bons, and Hur (2008, p. 1175): “The position to be presented here grows directly out of Darwin’s (1871) view that natural selection endowed modern humans with larger brains, increased levels of general and social intelligence, and a more ethical and prosocial personality than ’primeval man and his ape-like progenitors’ (p. 159). Darwin wrote of increased levels of human qualities such as ’courage, sympathy, and faithfulness,’ and a ’need for approval by others,’ with a concomitant decrease in the frequency of ’selfish and contentious people’ who ’will not cohere, and without coherence nothing can be effected’ (p. 159). Darwin described how moral and inter-personal skills go hand in hand with the greater intelligence modern people possess.” According to the evolutionary psychological perspective, we may reasonably expect that the Big Five should correlate in concordance with the evolutionary pressures in favor of adaptive function of each dimension. Thus, the Big Five correlations will form a stable pattern consisting of mutual positive correlations between Extraversion, Openness, Agreeableness, and Conscientiousness and negative correlations of these traits with Neuroticism. Consequently, we may also expect the positive manifold in correlation matrix of the Big Five, provided the reversal of Neuroticism to the Emotional Stability. And that is exactly the same correlation pattern being reported in the studies of GFP (Musek, 2007; Rushton & Irwing, 2008, 2009; Rushton et al., 2009). The question arises therefrom, which special model of evolution processes can be most efficiently applied to the emergence of the GFP? Two mutually connected theoretical approaches can be derived from the abovementioned Darwinian conceptual frame: the differential K theory and life history model. Both describe the evolutionary strategy, which supposes the coevolution of different personality traits being oriented toward the social benefits in human species.
DIFFERENTIAL K THEORY According to Wilson (1975), two opposed reproductive strategies can be traced in evolution: one producing a large number of fast-growing offspring with minimal parental care (r-strategy) and, a second, producing a small number of offspring with prolonged parental care and rearing (K-strategy). The organisms with r-strategy are smaller, short-lived, live in less stable and predictable environments, have a high-level of fecundity, and invest very little in the offspring. On the other hand, the organisms with K-strategy live
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Table 6.1 Typical differences in characteristics of r- and K-reproductive strategy Characteristic r-Organisms K-Organisms
Longevity Energy Intelligence Litters Reproduction Maturation Progeny Care of offspring Sex drive Birth size Social life Representative species
Short-lived Small Weak Wasting energy Low Large Early age Fast Quantity Little Strong Small Nonsocial Small rodents Salmons Insects Bacteria
Long-lived Big Strong Efficient energy handling High Small Late age Slow Quality Great Weak Large Social Humans Elephants Whales Arctic terns
longer, live in more stable and predictable environments, produce only a few progeny, and invest much more time and energy in them (see Table 6.1). Obviously, human beings occupy the very extreme on the K-strategy. Rushton et al. (2008, p. 1173) summarized the basic platform of differential K theory in the following formulation: “Twenty years ago, Rushton (1985, 1990) conjectured that ’one basic dimension—K—underlies much of the field of personality’ (1985, p. 445). He proposed that human social behavior is best understood as being part of a life-history—a suite of traits genetically organized to meet the trials of life—survival, growth, and reproduction. Building on Wilson (1975) theory of r-K reproductive strategies, which explains how animals colonize islands and reach population equilibrium, Rushton postulated that diverse personality traits covaried with altruism, intelligence, attachment styles, reproductive strategies, growth, longevity, and fecundity. Animals can adopt either of two strategies: produce a large number of fast maturing offspring but devote little parental care to ensure their survival (the r-strategy), or invest in a few slower-maturing, high quality offspring and devote considerable parental care to rearing them and ensuring that a much larger proportion survives (the K-strategy). Rushton dubbed his proposal ’Differential K Theory’ in order to emphasize that all humans were at the K-end of the continuum when compared against other species.”
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In this context, the introduction of the GFP (Musek, 2007) can be conceived as a confirmation of the general personality dimension, which was anticipated by Differential K Theory and corroborated also in the research in the line of the life history model (Figueredo, Vásquez, Brumbach, & Schneider, 2004, 2007; Figueredo et al., 2005, 2016). Indeed, the GFP is very substantially connected with different measures of prosocial orientation and social effectiveness (see Chapter 5) and represents a part of even more general Super-g factor, which embraces almost the entire domain of noncognitive traits (see Chapter 8). In this respect, the GFP can be easily compared and identified with the personality factor discovered by Figueredo et al. (2007).
LIFE HISTORY MODEL The evolution of personality including the GFP can be thus saliently explained in terms of Differential K Theory, which is further a part of the broader theoretical model labeled the “life history theory” (McArthur & Wilson, 1967; Wilson, 1975). Life history theory is focused on the differences in the allocation of energy and material resources in the adaptation to environment. Different species and also individual organisms vary between the orientation toward efficient mating and production of offspring (mating effort and reproductive effort) and orientation toward efficient survival of individual organism and offspring (somatic effort and parental effort). Organisms with r-reproductive strategy (see previous discussion) typically exhibit mating and reproductive effort, while organisms with K-reproductive strategy including humans manifest somatic and parental effort. In the excellent introduction into the evolutionary aspects of personality and GFP, Figueredo et al. (2016, p. 949) formulated the basic theoretical position as follows: “Evolutionary models of personality, such as those based in life history theory, have gone further by integrating the GFP into a broader life history super-factor termed Super-K, which encompasses behavioral manifestations of life history strategy and global measures of physical and mental health (this being the aforementioned covitality factor…). The life history model posits that the high-functioning pole of GFP relates to prosocial or altruistic orientations necessary for optimum fitness under conditions of low extrinsic mortality and morbidity where organisms exist at the carrying capacity of their environment and conspecific densities are high (Figueredo & Rushton, 2009).”
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The research in biology and psychology confirmed many hypotheses derived from life history theory and Differential K Theory (see an extensive review in Figueredo et al., 2016). The traits that can be connected with the K-reproductive strategy correlate and GFP represents a crucial dimension, which explains a lot of the shared variance in these traits (Figuredo et al., 2016, pp. 952–956). There is convincing evidence that variables of parental behavior and parenting style correlate with the well-being of children (Ellis, 2004). Figueredo et al. (2007) extracted a common factor underlying a variety of variables representing K-reproductive strategy or slow life history strategy in the large set of MIDUS I scales (Brim et al., 2000). The common slow life history factor (labeled the expanded K-factor) saturated variables like mother relationship quality, father relationship quality, marital relationship quality, children relationship quality, family support, altruism toward kin, friends’ close relationship quality, communitarian beliefs, religiosity, financial status, health control, agency, advice seeking, foresight/anticipation, insight into past, primary control/persistence, flexible/positive reappraisal, and self-directedness/planning (Figueredo et al., 2007, pp. 397–398). The expanded K-factor strongly correlated with the GFP (r = .66). In Chapter 8 we will report the results of the analysis of a large set of 32 MIDUS II variables (Ryff et al., 2007) where a very general common dimension was found (Comprehensive Factor of Personality or CFP), which also strongly correlates with the GFP (r = .70). If the analyses include the larger set of 63 variables, another general factor labeled Super-g was found. Super-g substantially correlated with the CFP (r = .49) and modestly with the GFP (r = .25), although the larger set includes the variables, which are not so closely related than 32 variables in first set. In the larger set we can find several variables that are not characteristic for the slow life history strategy.
GENETICS The mechanisms of evolution imply genetic effects on the involved characteristics. Personality dimensions are thus genetically shaped and heritable including the Big Five. In a large meta-analysis on the heritability of human traits, Polderman et al. (2015) reported 49% of heritable variance across 17,804 traits from 2748 publications including 14,558,903 twin pairs. Some (but not all) physical characteristics and cognitive abilities including
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intelligence have very high genetic components, while the heritability of values, attitudes, and beliefs is by the rule lower although often significant and even substantial (Eaves et al., 1999; Ludeke, Johnson, & Bouchard, 2013; Olson, Vernon, Jang, & Harris, 2001). According to Harris (2006), about 45% of the variance in personality is genetic, very little is accounted for by shared environment, and up to 55% to nonshared environment. It is therefore no mystery that the GFP, which accounts for the shared Big Five variance, is heritable too. In twin studies, the heritability of the Big Five was convincingly detected. According to these studies, the percent of the heritable variance in the Big Five is between 40 and 60 (Bouchard & McGue, 2003; Jang, Livesley, & Vernon, 1996; Jang et al., 2001; Loehlin et al., 1998; Vernon, Martin, Schermer, & Mackie, 2008). More detailed, the percent of genetic variation for “Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness was estimated at 41%, 53%, 61%, 41%, and 44%, respectively” (Jang et al., 1996, p. 577). However, the heritability measures yielded lower genetic influence in some studies, where the approaches other than twin research were applied. Power and Pluess (2015) found significant heritability only for Neuroticism and Openness and not Extraversion, Agreeableness, and Conscientiousness in a study using the Genomicrelatedness-matrix Residual Maximum Likelihood (GREML) analysis approach to genetic research. Yet, the heritability of extraversion was confirmed in another study using GREML (Vinkhuyzen et al., 2012). In the study, inaugurating the concept of the GFP (Musek, 2007), the heritability of the GFP was assumed but not directly measured. Very soon, Rushton et al. (2008) performed heritability analyses for 174 pairs of MZ twins and the 148 pairs of DZ twins on the GFP extracted from 29 self-rating scales. In regard to the heritability of the GFP, the authors claimed, “For the GFP itself, calculated using factor scores, the MZr = .55 and the DZr = .14, indicating evidence of genetic dominance and a heritability of 82%. Factor analyses performed on the genetic variance– covariance matrices (the G matrix) found a higher-order genetic GFP, which accounted for 32% of the genetic variance among the Big Five lower-order factors. (Going directly from the lower order traits to the Big One accounted for 28% of the genetic variance among those traits.)” (Rushton et al., 2008, p. 1179). Other twin studies also demonstrated considerable heritability of the GFP.Veselka, Schermer, Petrides, and Vernon (2009) conducted two studies, where the GFP was extracted from different personality scales. In both
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studies, the individual differences in the GFP were fully accounted for by genetic and nonshared environmental factors. Loehlin and Martin (2011) examined several thousand Australian twin pairs and confirmed the heritability of the GFP. The authors also demonstrated dominance effects of GFP, which were probably due to the dominance of the scales constituting the GFP. In the analysis of the MIDUS Twin sample, Figueredo et al. (2004, 2007; see also Figueredo & Rushton, 2009) compared the genetic correlations of three complex factors that were found across a large set of variables in the MIDUS survey data (Brim et al., 2000). The higher-order GFP correlated with the expanded K-factor (r = .66) and with the covitality factor (r = .36). All three factors have a very substantial genetic component, the GFP (h2 = .59), K-factor (h2 = .65), and covitality factor (h2 = .52). The genetic correlations between all three factors based on a large scale of traits suggest the integration of the several genetically regulated behavioral elements into a consistent reproductive strategy (Figueredo et al., 2011). Therefore, the authors deduced two important conclusions: “First, the genetic correlations among traits within each multivariate construct suggest that the higherorder levels of aggregation proposed as having merely heuristic utility may be neither intellectual conveniences nor statistical artifacts, but instead reflect a genuine functional integration of adaptive traits at the genetic level. Second, the genetic correlations among the higher-order constructs (the K-factor and the GFP) suggest that a correct application of Brunswik Symmetry identifies the level of biological organization at which the aggregates are functionally linked” (Figueredo et al., 2011, p. 398). Reanalyzing the data from MIDUS twin sample, Figueredo and Rushton (2009) found further evidence for the nonadditive effects in the genetic covariance between the GFP, general health factor, and life history factor. The authors summarized the evidence for shared genetic dominance among three factors as follows: “We suggest these genetic correlations support the view that a slow (K-selected) life history strategy, good health and the GFP coevolved and are mutually coadapted through directional selection” (Figueredo & Rushton, 2009, p. 555).
GFP IN THE LIGHT OF NEUROSCIENCE Neural Correlates of Personality Personality traits have been often examined by means of neuroscientific approaches including the research of neurological, neurophysiological, and
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neurochemical effects. For example, all Big Five dimensions have been extensively investigated in connection to the cortical and subcortical brain functioning including the functions of basic neural structures and their associations (Rodrigo et al., 2015). The connections of personality traits to the neurotransmitter systems with the respective neurophysiological and neurochemical aspects have been also investigated in many studies (Depue & Collins, 1999). However, the neuroscientific aspects of personality are very complex and far from being thoroughly investigated. With regard to the GFP, we should therefore focus on efficient strategy in order to identify possible neuroscientific correlates. A promising strategy may be in trying to find the answers to the question, which neuroscientific factors must be considered to explain the functional coordination of high emotional stability (low neuroticism), extraversion, conscientiousness, agreeableness, and openness versus the opposite. Pure logic implies that this combination of the Big Five, which is typical for the GFP, may at the personality level represent socially acceptable and desirable control of our behavior, emotions, and thoughts (e.g., inhibitory control). The inhibitory control can be defined as the ability to control our behavior, emotions, and cognitions in order to adapt to our natural and social environment (Cahn-Weiner, Malloy, Boyle, Marran, & Salloway, 2000; Hasher, Zacks, & May, 1999; Rodrigo et al., 2015; Verbruggen & Logan, 2008). The inhibitory control is thus necessary for socially adequate behavior, which is associated with personality traits including the GPF.
Inhibitory Control and Prefrontal Cortex Musek (2007) already speculated that the correlations among the Big Five, which underlie the GFP, might be connected to the neural mechanisms that influence the activity of two great neurophysiological systems, the serotonergic and dopaminergic system, respectively. Both systems are important in relation to inhibitory control, especially the combination of increased dopaminergic and suppressed serotonergic neural activation. According to the author (p. 1228), the GFP could be linked to the “biological mechanism combining low levels of the functioning of the central serotonergic system (Spoont, 1992;Tork, 1990) and higher levels of the functioning of ascending rostral dopaminergic system (Ashby, Isen, & Turken, 1999; Davidson, 1995, pp. 361–387; Depue & Collins, 1999; Panksepp, 1999; Pauls, Wacker, & Crost, 2005). This combination has been implicated in the higher values of Stability and Plasticity factors (DeYoung et al., 2001) that, according to the present results, constitute the Big One. Given the heritability of the Big
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Five, it is possible that speculated covariation of dopaminergic and serotonergic system is genetically mediated.” Yet, which neural mechanism could be responsible for raising the emotional stability (lowering neuroticism), conscientiousness, agreeableness, extraversion, and openness? Exactly this question was posed by Rushton et al. (2008, p. 1181): “What neurological substrates might evolution lay down to increase the GFP and improve inter-personal efficiency? One straightforward possibility is adding neural tracts in the frontal cortex, which is responsible for self-control and forward planning. A large body of evidence now supports the ’social brain-social complexity’ hypothesis. For example, across species of primates, there is a strong positive correlation between the size of the neocortex (relative to body size) and the larger the group size, which is a function of how many individuals in a group can be recognized and how much information can be processed… It has been well known since the famous case of Phineas T. Gage that damage to the frontal cortex, reduces conscientiousness and disinhibits aggressive, impulsive, and anti-social behavior…, and also lowers fluid intelligence and judgment…” The prefrontal cortex is almost certainly involved in the processes of inhibitory control, although the activation of other cortical regions and structures has also been observed (see the meta-analysis of 47 functional magnetic resonance imaging (fMRI) studies by Swick, Ashley, & Turken, 2011). It seems that the prefrontal cortex, especially the right inferior frontal gyrus, are the structures that are of the utmost importance in the functioning of the inhibitory control (Aron, Robbins, & Poldrack, 2004; Chikazoe, Konishi, Asari, Jimura, & Miyashita, 2007). Unfortunately, there is very little research examining the connections between the Big Five and functional activation of the prefrontal cortical structures. However, the few studies that are relevant in this respect strongly indicated the role of the prefrontal activation in the GFP. These studies used a rather recent methodology, fMRI and near-infrared spectroscopy(fNIRS) in functional detection of neural personality correlates (Eisenberger, Lieberman, & Satpute, 2005; Forbes et al., 2014; Rodrigo et al., 2015; Sosic-Vasic, Ulrich, Ruchsow, Vasic, & Gron, 2012). Using fNIRS, Rodrigo et al. (2015) discovered that greater activation of lateral region of the prefrontal cortex was associated with higher levels of extraversion, agreeableness, and consciousness and with lower levels of neuroticism. This is exactly the pattern of the Big Five that is typical for the high level of GFP. The authors (p. 1) concluded that “these results suggest that personality traits reflecting greater emotional stability, extraversion, agreeableness and conscientiousness may be associated with more efficient recruitment of control
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processes subserved by lateral regions of the prefrontal cortex.” Why we can be so certain that the detected pattern of personality–prefrontal cortex relation should reflect the GFP? It is so because we can exclude the possibility that the Big Five in the study of Rodrigo et al. (2015) do not correlate and therefore do not constitute the GFP. Instead, the Big Five correlated in the manner typical for the GFP (p. 4).The authors did not calculate the GFP, but if we reexamine the reported Big Five correlations, the GFP clearly emerges saturating neuroticism (−.64), extraversion (.58), agreeableness (.40), conscientiousness (.37), and openness (.17). If the GFP would be calculated, its connections to the activation of the prefrontal cortex would be greater than those of any single Big Five dimension. Relative activation of the prefrontal cortex can be indicated also by measuring the respective asymmetries in allocated brain functions. Thus, the frontal left to right alpha asymmetry can serve as an index of the prefrontal activity. According to Sutton and Davidson (1997), higher left resting prefrontal activity is associated with the behavioral activation system (BAS) and higher right prefrontal activation with the behavioral inhibitory system (BIS), and similar although less clear difference in relative prefrontal activity was observed for the positive and negative affect (Figueredo et al., 2011, pp. 397–380). These findings can be indirectly connected with the GFP, which is related to BAS-BIS systems and affect. The GFP correlates positively with BAS and positive affect and negatively with BIS and negative affect. Thus, if the inhibitory control is associated with the greater left prefrontal cortical activation, we can hypothesize that higher GFP would be connected with the greater frontal alpha asymmetry in EEG. Uibo, Allik, and Hiettanen (2012) discovered that extraverted and emotionally stable persons exhibit greater positive frontal alpha asymmetry (more activation in the right side) in gaze direction behavior. The greater activation of frontal over posterior regions was found in extraverted, emotionally stable, and conscientious individuals. These results, which may be indicative also for the differences in GFP, indicate the role of the frontal region in approach versus avoidant behavior (the former being characteristic for higher GFP). More direct connection of the EEG alpha asymmetries and GFP can be obtained by analyzing the MIDUS II neurological data (Ryff & Davidson, 2010, p. v1). According to our very robust analyses, the GFP significantly correlates with C3/C4 alpha asymmetry (r = .19), maybe reflecting the brain activities associating frontal and central cortical regions (Musek, 2016). Yet, caveat! The associations between the GFP and prefrontal activation do not mean that the personality is not involved into the functioning of
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other different cortical structures and their associations. Personality traits very probably have extremely complex connections to numerous brain functions, associations, and structurations, which are not yet satisfactorily investigated (Figueredo et al., 2011; Yarkoni, 2015). However, the relations of the GFP to the inhibitory control and prefrontal activation should be very informative for the biological understanding of the personality.
Affect, Amygdala and Limbic System The GFP may be linked with still other neural substrates, especially if we consider the connections of the GFP with other domains of psychological variables as affect, well-being, self-esteem, coping, mental health, etc. (see also Chapter 8). Personality dimensions are linked with affect: neuroticism with negative affect and extraversion with positive affect, while less extensive connections with both affects have been observed in other personality dimensions too (Steel, Schmidt, & Shultz, 2008). Yet, both dimensions of affect are also inherent in other different domains of noncognitive psychological variables, especially in well-being and mental health. Moreover, some biological bases of both affects have been reliably discovered. The role of amygdala in processing affect was known for a long time and was also recently clearly confirmed (Jin, Zelano, Gottfried, & Mohanty, 2015). According to the large meta-analysis of fMRI investigations, Lindquist, Satpute,Wager,Weber, and Barrett (2016) concluded that a set of limbic and paralimbic brain regions balance negative and positive affect. Thus, the research evidence has not confirmed the separate regulation of positive and negative affect so far. Recent research shows also that negative affect is more heritable than positive affect (Zheng, Plomin, & von Stumm, 2016). Thus, the limbic and paralimbic structures with their cortical associations also may be linked with the Big Five correlations and consequently with the GFP.
CONCLUSIONS From the theoretical point of view, the GFP can be postulated within the biological framework consisting of modern concepts of evolution, supported by genetic and neuroscientific evidence. Thus, the GFP can be cogently conceptualized within the solid frame of modern and even classic theory of evolution with all necessary genetic and neuroscientific apparatus. From the standpoint of the theory of evolution, the GFP should be interpreted in the context of the life history theory and Differential K Theory. Both predict the coevolution of personality traits,
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which are oriented toward the social benefits in human species. The evolutionary background of the GFP implies the genetic basis that should be realized through the functioning of the neural structures and associations that are involved in the processing of the Big Five correlations constituting GFP. The genetic research clearly proved the heritability of GFP and the neuroscientific research strongly suggests that GFP should be linked with the inhibitory control and the activation of prefrontal cortex and limbic structures. Thus, the theory of evolution represents a theoretical framework of the GFP construct. The evolutionary basis of the GFP is further corroborated by extensive genetic and neuroscientific research demonstrating the substantial heritability of the GFP and possible neurological, neurophysiological, and neurochemical factors connected with the GFP. The biological basis renders the GFP not only an empirically supported construct but also a construct that has a salient theoretical foundation.
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