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Pedigree-based analyses of intelligence have reported that genetic differences account for 50-80% of the phenotypic variation. For personality traits these effects are smaller, with 34-48% of the variance being explained by genetic differences. However, molecular genetic studies using unrelated individuals typically report a heritability estimate of around 30% for intelligence and between 0% and 15% for personality variables. Pedigree-based estimates and molecular genetic estimates may differ because current genotyping platforms are poor at tagging causal variants, variants with low minor allele frequency, copy number variants, and structural variants. Using ~20 000 individuals in the Generation Scotland family cohort genotyped for ~700 000 single nucleotide polymorphisms (SNPs), we exploit the high levels of linkage disequilibrium (LD) found in members of the same family to quantify the total effect of genetic variants that are not tagged in GWASs of unrelated individuals. In our models, genetic variants in low LD with genotyped SNPs explain over half of the genetic variance in intelligence, education, and neuroticism. By capturing these additional genetic effects our models closely approximate the heritability estimates from twin studies for intelligence and education, but not for neuroticism and extraversion. We then replicated our finding using imputed molecular genetic data from unrelated individuals to show that ~50% of differences in intelligence, and ~40% of the differences in education, can be explained by genetic effects when a larger number of rare SNPs are included. From an evolutionary genetic perspective, a substantial contribution of rare genetic variants to individual differences in intelligence and education is consistent with mutation-selection balance.
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While a large body of research has investigated cultural differences in behavior, this typical study assesses a single behavioral outcome, in a single context, compared across two countries. The current study compared a broad array of behaviors across 21 countries (N = 5,522). Participants described their behavior at 7:00 p.m. the previous evening using the 68 items of the Riverside Behavioral Q-sort (RBQ). Correlations between average patterns of behavior in each country ranged from r = .69 to r = .97 and, in general, described a positive and relaxed activity. The most similar patterns were United States/Canada and least similar were Japan/United Arab Emirates (UAE). Similarities in behavior within countries were largest in Spain and smallest in the UAE. Further analyses correlated average RBQ item placements in each country with, among others, country-level value dimensions, personality traits, self-esteem levels, economic output, and population. Extroversion, openness, neuroticism, conscientiousness, self-esteem, happiness, and tolerant attitudes yielded more significant correlations than expected by chance.
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By comparing alternative evolutionary models, the International Sexuality Description Project marks the transition of evolutionary psychology to the next level of scientific maturation. The lack of final conclusions might partly be a result of the composition of the Sociosexual Orientation Inventory and the sampled populations. Our own data suggest that correcting for both gives further support to the strategic pluralism model.
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A major problem with Implicit Association Tests (IATs) is that they require bipolar attributes (e.g., good-bad). Thus, IAT effects for an attribute category can be interpretated only relative to an opposite category. Problems arise if there is no clear opposite category; in this case a neutral category can be used, although it induces systematic error variance and thus reduces validity. The present study suggests that this problem can be solved using single-attribute IATs (SA-IATs). Sociosexuality (the tendancy to engage in uncommited sex) was expected to be related at the implicit level to stronger stranger-sex associations. An IAT was constructed that used conversation as a neutral attribute, it showed satisfactory reliability but only low correlations with explicit sociosexuality. An alternative SA-IAT with sex as the only attribute showed a similar reliability but higher correlations with explicit sociosexuality.
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Studies of women's preferences for male faces have variously reported preferences for masculine faces, preferences for feminine faces and no effect of masculinity-femininity on male facial attractiveness. It has been suggested that these apparently inconsistent findings are, at least partly, due to differences in the methods used to manipulate the masculinity of face images or individual differences in attraction to facial cues associated with youth. Here, however, we show that women's preferences for masculinity manipulated in male faces using techniques similar to the three most widely used methods are positively inter-related. We also show that women's preferences for masculine male faces are positively related to ratings of the masculinity of their actual partner and their ideal partner. Correlations with partner masculinity were independent of real and ideal partner age, which were not associated with facial masculinity preference. Collectively, these findings suggest that variability among studies in their findings for women's masculinity preferences reflects individual differences in attraction to masculinity rather than differences in the methods used to manufacture stimuli, and are important for the interpretation of previous and future studies of facial masculinity.
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Most theories of human mental evolution assume that selection favored higher intelligence and larger brains, which should have reduced genetic variance in both. However, adult human intelligence remains highly heritable, and is genetically correlated with brain size. This conflict might be resolved by estimating the coefficient of additive genetic variance (CVA) in human brain size, since CVAs are widely used in evolutionary genetics as indexes of recent selection. Here we calculate for the first time that this CVA is about 7.8, based on data from 19 recent MRI studies of adult human brain size in vivo: 11 studies on brain size means and standard deviations, and 8 studies on brain size heritabilities. This CVA appears lower than that for any other human organ volume or life-history trait, suggesting that the brain has been under strong stabilizing (average-is-better) selection. This result is hard to reconcile with most current theories of human mental evolution, which emphasize directional (more-is-better) selection for higher intelligence and larger brains. Either these theories are all wrong, or CVAs are not as evolutionarily informative as most evolutionary geneticists believe, or, as we suggest, brain size is not a very good index for understanding the evolutionary genetics of human intelligence. (c) 2006 Published by Elsevier Inc.
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Most commentaries welcomed an evolutionary genetic approach to personality, but several raised concerns about our integrative model. In response, we clarify the scientific status of evolutionary genetic theory and explain the plausibility and value of our evolutionary genetic model of personality, despite some shortcomings with the currently available theories and data. We also have a closer look at mate choice for personality traits, point to promising ways to assess evolutionarily relevant environmental factors and defend higher-order personality domains and the g-factor as the best units for evolutionary genetic analyses. Finally, we discuss which extensions of and alternatives to our model appear most fruitful, and end with a call for more inter-disciplinary personality research grounded in evolutionary theory.
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Genetic influences on personality differences are ubiquitous, but their nature is not well understood. A theoretical framework might help, and can be provided by evolutionary genetics. We assess three evolutionary genetic mechanisms that could explain genetic variance in personality differences: selective neutrality, mutation-selection balance, and balancing selection. Based on evolutionary genetic theory and empirical results from behaviour genetics and personality psychology, we conclude that selective neutrality is largely irrelevant, that mutation-selection balance seems best at explaining genetic variance in intelligence, and that balancing selection by environmental heterogeneity seems best at explaining genetic variance in personality traits. We propose a general model of heritable personality differences that conceptualises intelligence as fitness components and personality traits as individual reaction norms of genotypes across environments, with different fitness consequences in different environmental niches. We also discuss the place of mental health in the model. This evolutionary genetic framework highlights the role of gene-environment interactions in the study of personality, yields new insight into the person-situation-debate and the structure of personality, and has practical implications for both quantitative and molecular genetic studies of personality.
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Based on undergraduates' self-reports of mate preferences for various traits and self-perceptions of their own levels on those traits, Buston and Emlen [Buston PM, Emlen ST (2003) Proc Natl Acad Sci USA 100:8805-8810] concluded that modern human mate choices do not reflect predictions of tradeoffs from evolutionary theory but instead follow a ``likes-attract'' pattern, where people choose mates who match their self-perceptions. However, reported preferences need not correspond to actual mate choices, which are more relevant from an evolutionary perspective. In a study of 46 adults participating in a speed-dating event, we were largely able to replicate Buston and Emlen's self-report results in a pre-event questionnaire, but we found that the stated preferences did not predict actual choices made during the speed-dates. Instead, men chose women based on their physical attractiveness, whereas women, who were generally much more discriminating than men, chose men whose overall desirability as a mate matched the women's self-perceived physical attractiveness. Unlike the cognitive processes that Buston and Emlen inferred from self-reports, this pattern of results from actual mate choices is very much in line with the evolutionary predictions of parental investment theory.
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The purpose of this study was to investigate the influence of men's sociosexual orientation on their perceptions of women's physical attractiveness, health and fertility. Fifty British mate participants were assigned to two groups (restricted versus unrestricted) based on their responses to items on the Revised Sociosexual Orientation Inventory. Participants rated the attractiveness, health and fertility of a series of 50 photographs of women varying in body mass index (BMI) and waist-to-hip ratio (WHR). Results suggested that both groups of men based their judgements primarily on BMI rather than WHR. However, there were significant between-groups differences: unrestricted men judged women with a lower BMI as more attractive, healthy and fertile than restricted men. Unrestricted men also showed a stronger preference for women with a low WHR. The results support a dynamic psychological model of interpersonal attraction, which many earlier studies have neglected. (C) 2007 Elsevier Ltd. All rights reserved.
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The two evolutionary psychological hypotheses that men react more jealous than women to sexual infidelity and women react more jealous than men to emotional infidelity are currently controversial because of apparently inconsistent results. We suggest that these inconsistencies can be resolved when the two hypotheses are evaluated separately and when the underlying cognitive processes are considered. We studied jealousy with forced-choice decisions and emotion ratings in a general population sample of 284 adults aged 20-30 years using six infidelity dilemmas and recordings of reaction times. The sex difference for emotional jealousy existed for decisions under cognitive constraint, was also evident in the decision speed, increased for faster decisions, and was stronger for participants with lower education. No evidence for a sex difference in sexual jealousy was found. Our results support the view of a specific female sensitivity to emotional infidelity that canalizes the development of an adaptive sex difference in emotional jealousy conditional to the sociocultural environment. Copyright (c) 2007 John Wiley & Sons, Ltd.
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People have a fundamental need to belong that motivates them to seek out social interactions with close others (Baumeister & Leary, 1995). Leary and Baumeister's (2000) sociometer theory (SMT) poses that people who succeed in satisfying this need have higher self-esteem (SE). This prediction was tested across three hierarchical levels: intraindividual, interindividual, and international. Indicators of social interaction quantity, quality, and the interaction between quality and quantity were collected for relationships with friends, family members, and romantic partners. On the intraindividual level, relationship quality and the interaction between quantity and quality emerged as significant predictors of daily fluctuations in SE. Cross-lagged analyses indicated that this association is at least partly due to the effect of social inclusion on changes in SE. On an interindividual level, people who generally reported higher quality relationships also had higher levels of trait SE. On an international level, countries whose inhabitants regularly interact with friends were characterized by higher nationwide SE levels than countries without such practices, even when happiness, individualism, gross domestic product, and neuroticism were controlled.
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It has been suggested that self-esteem is reactive to signs of social rejection, and that this ``sociometer'' mechanism becomes attuned to those personal attributes that affect social acceptance by significant others. Based on evolutionary models of human mating, we predicted that self-esteem should be more attuned to self-perceived mate value in men (when compared to women) who pursue short-term mating tactics, especially if they are unsuccessful therein. In a web-based study (N=2670), we found that mate value self-perceptions had a stronger effect on self-esteem on those who had less short-term mating success in the past. However, being in a committed relationship or parenthood reduced the impact of mate value self-perceptions. As expected, these effects were specific to men. These results are suggestive of a psychological mechanism based on adaptive sociometer attunements that could help men to choose their optimal mating tactic and might thus partly explain intrasexual differences in sociosexuality. (c) 2008 Elsevier Inc. All rights reserved.
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In spite of its popularity, the Five-Factor Model (FFM) has been criticized for being too descriptive to provide a theoretical model of personality. The current article conceptualizes the FFM as stable individual differences in people's motivational reactions to circumscribed classes of environmental stimuli. Specifically, extraversion was conceptualized as individual differences in the activation of reward system in social situations, agreeableness as differences in the motivation to cooperate (vs. acting selfishly) in resource conflicts, conscientiousness as differences in the tenacity of goal pursuit under distracting circumstances, neuroticism as differences in the activation of the punishment system when faced with cues of social exclusion, and openness for experiences as differences in the activation of reward system when engaging in cognitive activity. We devised a questionnaire that is consistent with these motivational conceptualizations. This questionnaire turned out to differ from an established FFM questionnaire in terms of content but it did not interfere with the factorial, structural, and predictive validity of the FFM. The resulting theoretical framework may help to bridge the traditional divide between structure- and process-oriented approaches in personality psychology. (C) 2008 Elsevier Inc. All rights reserved.
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In the current paper we hypothesized that people who are high in neuroticism (N) share a motivational predisposition to react vigilantly to threatening cues, most of which tend to be social in humans. In three studies, support for this prediction was found: based on cross-sectional and diary data, it was,found that the self-esteem (SE) of individuals high in N decreases more in response to perceptions of relationship conflict and low relationship quality than that of emotionally stable ones. In a study of people's reactions to imagined threats, neurotic individuals showed a heightened sensitivity to both nonsocial and social cues, though reactions to social cues were somewhat more pronounced. Results are consistent with principles from evolutionary and process-oriented personality psychology. Copyright (C) 2008 John Wiley & Sons, Ltd.
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The present study examines the effects of six weather parameters (temperature, wind power, sunlight, precipitation, air pressure, and photoperiod) on mood (positive affect, negative affect, and tiredness). Data were gathered from an online diary study (N = 1,233), linked to weather station data, and analyzed by means of multilevel analysis. Multivariate and univariate analyses enabled distinction between unique and shared effects. The results revealed main effects of temperature, wind power, and sunlight on negative affect. Sunlight had a main effect on tiredness and mediated the effects of precipitation and air pressure on tiredness. In terms of explained variance, however, the average effect of weather on mood was only small, though significant random variation was found across individuals, especially regarding the effect of photoperiod. However, these individual differences in weather sensitivity could not be explained by the Five Factor Model personality traits, gender, or age.
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Sociosexuality is usually assessed as the overall orientation toward uncommitted sex, although this global approach may mask unique contributions of different components. In a large online study (N = 2,708) and a detailed behavioral assessment of 283 young adults (both singles and couples) with a 1-year follow-up, the authors established 3 theoretically meaningful components of sociosexuality: past behavioral experiences, the attitude toward uncommitted sex, and sociosexual desire (all measured by a revised version of the Sociosexual Orientation Inventory). Discriminant validity was shown with regard to (a) their factorial structure, (b) sex differences, (c) many established correlates of sociosexuality, and (d) the prediction of observed flirting behavior when meeting an attractive opposite-sex stranger, even down to the level of objectively coded behaviors, as well as (e) the self-reported number of sexual partners and (f) changes in romantic relationship status over the following year. Within couples, the 3 components also showed distinct degrees of assortative mating and distinct effects on the romantic partner. Implications for the evolutionary psychology of mating tactics are discussed.
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The ability to judge another individual's romantic interest level-both toward oneself and toward others-is an adaptively important skill when choosing a suitable mate to pursue. We tested this ability using videos of individuals on speed dates as stimuli. Male and female observers were equally good at predicting interest levels, but they were more accurate when predicting male interest: Predictions of female interest were just above chance. Observers predicted interest successfully using stimuli as short as 10 s, and they performed best when watching clips of the middle or end of the speed date. There was considerable variability between daters, with some being very easy to read and others apparently masking their true intentions. Variability between observers was also found. The results suggest that the ability to read nonverbal behavior quickly in mate choice is present not only for individuals in the interaction, but also for third-party observers.
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Del Giudice's model belongs among those that highlight the role of adaptive developmental plasticity in human reproductive strategies; but at least three other forms of evolutionary adaptation also influence reproductive behavior. Similar to earlier models, the existing evidence suggests that Del Giudice's hypothesized effects are rather weak. In particular, adult attachment styles are hardly predictive of outcomes visible to natural selection.
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While Furr (this issue) makes many important contributions to the study of behaviour, his definition of behaviour is somewhat questionable and also lacks a broader theoretical frame. I provide some historical and theoretical background on the study of behaviour in psychology and biology, from which I conclude that a general definition of behaviour might be out of reach. However, psychological research can gain from adding a functional perspective on behaviour in the tradition of Tinbergens's four questions, which takes long-term outcomes and fitness consequences of behaviours into account. Copyright (C) 2009 John Wiley & Sons, Ltd.
