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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.
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It has been proposed that a common cause underlies individual differences in bodily and cognitive decline in old age. No good marker for this common cause has been identified to date. Here, fluctuating asymmetry (FA), an indicator of developmental stability that relates to intelligence differences in young adults, was measured from facial photographs of 216 surviving members of the Lothian Birth Cohort 1921 at age 83 and related to their intelligence at ages 11, 79 and 83 years. FA at age 83 was unrelated to intelligence at ages I I and 79 and to cognitive change between 11 and 79 years. It was, however, associated with intelligence and information processing efficiency at age 83 and with cognitive change between 79 and 83 years. Significant results were limited to men, a result predicted by sex differences in life history tradeoffs and life expectancy. Results were stronger when directional asymmetries were corrected in facial FA measures. Thus, FA is a candidate marker for the common cause of differential senescence. (C) 2009 Elsevier Inc. All rights reserved.
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Age-associated cognitive decline-or normal (non-pathological, normative, usual) cognitive ageing-is an important human experience which differs in extent between individuals. The determinants of the differences in age-related cognitive decline are not fully understood. Progress in the field is taking place across many areas of biomedical and psychosocial sciences. The phenotype of normal cognitive ageing is well described. Some mental capabilities are well maintained into old age. From early adulthood, there are declines in mental domains such as processing speed, reasoning, memory and executive functions, some of which is underpinned by a decline in a general cognitive factor. There are contributions to understanding individual differences in normal cognitive ageing from genetics, general health and medical disorders such as atherosclerotic disease, biological processes such as inflammation, neurobiological changes, diet and lifestyle. Many of these effect sizes are small; some are poorly replicated; and in some cases, there is the possibility of reverse causation, with prior cognitive ability causing the supposed `cause' of cognitive ability in old age. Genome-wide scans are a likely source to establish genetic contributions. The role of vascular factors in cognitive ageing is increasingly studied and understood. The same applies to diet, biomarkers such as inflammation and lifestyle factors such as exercise. There are marked advances in brain imaging, affording better in vivo studies of brain correlates of cognitive changes. There is growing appreciation that factors affecting general bodily ageing also influence cognitive functions in old age.
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Four evolutionary-developmental models within a life history theory framework were compared as to their predictions of the influences of family of origin on age at menarche and differences in reproductive strategies. Predictions of paternal investment theory (Draper Harpending, 1982), psychosocial acceleration theory (Belsky, Steinberg, Draper, 1991), polygyny indication model (Kanazawa, 2001), and child development theory (Ellis, 2004) were tested by structural equation modelling in an internet study of 439 women between the ages of 18 and 30. Results show that the existence of a father figure has an impact on the age at menarche, which influences the age at first sexual intercourse. The directions of influences confirm the predictions of paternal investment theory (Draper Harpending, 1982), psychosocial acceleration theory (Belsky et al., 1991), and child development theory (Ellis, 2004), but not the predictions of the polygyny indication model (Kanazawa, 2001). No significant associations could be found between age at menarche and other reproductive strategy markers; this supports one of the central assumptions of child development theory (Ellis, 2004). Instead, it was the age at first sexual intercourse, influenced by the age at menarche, the existence of a father figure, and participant's educational level, that was most critical for the future reproductive strategies.
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Neuroscience is contributing to an understanding of the biological bases of human intelligence differences. This work is principally being conducted along two empirical fronts: genetics - quantitative and molecular - and brain imaging. Quantitative genetic studies have established that there are additive genetic contributions to different aspects of cognitive ability - especially general intelligence - and how they change through the lifespan. Molecular genetic studies have yet to identify reliably reproducible contributions from individual genes. Structural and functional brain-imaging studies have identified differences in brain pathways, especially parieto-frontal pathways, that contribute to intelligence differences. There is also evidence that brain efficiency correlates positively with intelligence.
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It has recently been reported that the evolutionarily ancestral alleles of two functional polymorphisms in the beta(2)-adrenergic receptor gene (ADRB2) were related to higher cognitive ability in the 70 year old participants of the Lothian Birth Cohort 1936 (LBC1936). One emerging important factor in cognitive aging is the integrity of white matter tracts in the brain. Here, we used diffusion tensor MRI-based tractography to assess the integrity of eight white matter tracts in a subsample of the LBC1936. Higher integrity of the splenium of the corpus callosum predicted better cognitive ability in old age, even after controlling for IQ at age 11. Also, the ancestral allele of one ADRB2 SNP was associated with both splenium integrity and better cognitive aging. While the effects of the SNP and splenium integrity on cognitive aging were largely independent, there was some evidence for a partial mediation effect of ADRB2 status via splenium integrity.
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Latent variable modeling has revealed important conundrums in the DSM classification system. We agree that the network perspective has potential to inspire new insights and resolve some of these conundrums. We note, however, that alone it cannot really help us understand etiology. Etiology, not comorbidity, is the fundamental question.
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Human white matter integrity has been related to information processing speed, but it is unknown whether impaired integrity results from localized processes or is a general property shared across white matter tracts. Based on diffusion MRI scans of 132 healthy individuals with a narrow age range around 72 years, the integrity of eight major white matter tracts was quantified using probabilistic neighborhood tractography. Principal component analyses (PCAs) were conducted on the correlations between the eight tracts, separately for four tract-averaged integrity parameters: fractional anisotropy, mean diffusivity, and radial and axial diffusivity. For all four parameters, the PCAs revealed a single general factor explaining similar to 45\% of the individual differences across all eight tracts. Individuals' scores on a general factor that captures the common variance in white matter integrity had significant associations with a general factor of information processing speed for fractional anisotropy (r = -0.24, p = 0.007) and radial diffusivity (r = 0.21, p = 0.016), but not with general intelligence or memory factors. Individual tracts showed no associations beyond what the common integrity factor explained. Just as different types of cognitive ability tests share much of their variance, these novel findings show that a substantial amount of variance in white matter integrity is shared between different tracts. Therefore, impaired cortical connection is substantially a global process affecting various major tracts simultaneously. Further studies should investigate whether these findings relate more to the role of tract integrity and information processing speed in nonpathological cognitive aging or in lifelong-stable processes.
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Charlton et al (2008) (Charlton, R A, Landua, S Schiavone, F Barrick, T R. Clark, C A, Markus, H S, Morris. R G A, 2008 Structural equation modelling investigation of age-related variance in executive function and DTI-measured white matter change Neurobiol Aging 29, 1547-1555) presented a model that suggests a specific age-related effect of white matter integrity on working memory. We illustrate potential pitfalls of structural equation modelling by criticizing their model for (a) Its neglect of latent variables. (b) its complexity, (c) Its questionable causal assumptions, (d) the use of empirical model reduction, (e) the mix-up of theoretical perspectives, and (f) the failure to compare alternative models We show that a more parsimonious model, based solely on the well-established general factor of cognitive ability, fits their data at least as well Importantly, when modelled this way there is no support for a role of white matter integrity in cognitive aging in this sample, indicating that their conclusion is strongly dependent on how the data are analysed. We suggest that evidence from more conclusive study designs is needed (C) 2009 Elsevier Inc All rights reserved
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When searching for a mate, one must gather information to determine the mate value of potential partners. By focusing on individuals who have been previously chosen by others, one's selection of mates can be influenced by another's successful search a phenomenon known as mate copying. We show mate copying in humans with a novel methodology that closely mimics behavioral studies with non-human animals. After observing instances of real mating interest in video recordings of speed-dates, both male and female participants show mate copying effects of heightened short-term and long-term relationship interest towards individuals in dates they perceived as successful. Furthermore, the relative attractiveness of observers and observed plays a mediating role in whom an individual will choose to copy. (C) 2010 Elsevier Inc. All rights reserved.
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The concept of personality has recently begun to attract a great deal of interest in behavioural ecology. However, there is also a large and mature literature on personality within human psychology. These two bodies of work have developed independently and at present make rather little reference to one another. The current paper has two main objectives. First, we seek to acquaint behavioural ecologists with the principal ideas and issues found in the human personality psychology literature. Second, we explore how ideas from the behavioural ecology literature might help advance research in human personality psychology. We suggest strong potential for convergence between the two literatures in the near future. Common themes of this future unified science of personality include the conception of personality traits as reaction norms, a commitment to the importance of direct measurement of behaviour, investigation of both proximate and ultimate explanations for personality variation, and a concern with the impact of personality variation on survival and reproductive success.
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The relationship between Fluctuating Asymmetry (FA) and personality can cast light on the fitness con sequences and selective benefits underlying personality However few studies have investigated the topic and these have rendered inconsistent findings Theoretically predicted relationships of FA to personality include linear associations and curvilinear associations (with low FA leading to average-not extreme-personality trait levels) Evidence for no association would suggest that personality has no consequences for general fitness We summarise the findings to date adding two new studies testing each of the hypothesised models with well-validated measures of FA and personality traits No consistent associations were found Though it remains possible that low FA is weakly related to conscientiousness and openness to experience the major personality domains seem unrelated to FA (C) 2010 Elsevier Ltd All rights reserved
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We studied initial and long-term outcomes of speed-dating over a period of 1 year in a community sample involving 382 participants aged 18-54 years. They were followed from their initial choices of dating partners up to later mating (sexual intercourse) and relating (romantic relationship). Using Social Relations Model analyses, we examined evolutionarily informed hypotheses on both individual and dyadic effects of participants' physical characteristics, personality, education and income on their dating, mating and relating. Both men and women based their choices mainly on the dating partners' physical attractiveness, and women additionally on men's sociosexuality, openness to experience, shyness, education and income. Choosiness increased with age in men, decreased with age in women and was positively related to popularity among the other sex, but mainly for men. Partner similarity had only weak effects on dating success. The chance for mating with a speed-dating partner was 6\%, and was increased by men's short-term mating interest; the chance for relating was 4\%, and was increased by women's long-term mating interest. Copyright (C) 2010 John Wiley & Sons, Ltd.
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Personality traits do not exist in a vacuum, they are only meaningful if they are considered together with situations where they lead to the expressions of behaviours. Simply put personality and situations are intimately intertwined in the generation of behaviour.
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Based on a social relations perspective on mating, the actual and assumed reciprocity of mate choices was studied in a real-life speed-dating context. A community sample involving 382 singles aged 18-54 years filled out a questionnaire for the measurement of self-perceived mate value, sociosexuality, extraversion, and shyness and participated in free speed-dating sessions. Immediately after each date, choices and assumed choices were recorded. Measures of physical attractiveness and flirting behaviour were obtained by independent observers. Results show that actual mate choices are not reciprocal although people strongly expect their choices to be reciprocated and flirting behaviour is indeed strongly reciprocal. This interesting pattern of results was explained by investigating individual and dyadic effects of flirting, self-perceived mate value and physical attractiveness on mate choices. Results have important implications for understanding mating behaviour, sex differences and the (in) accuracies of mating decisions. Copyright (C) 2010 John Wiley & Sons, Ltd.
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The interplay of personality and social relationships is as fascinating as it is complex and it pertains to a wide array of largely separate research domains. Here, we present an integrative and unified framework for analysing the complex dynamics of personality and social relationships (PERSOC). Basic principles and general processes on the individual and dyadic level are outlined to show how personality and social relationships influence each other and develop over time. PERSOC stresses the importance of social behaviours and interpersonal perceptions as mediating processes organized in social interaction units. The framework can be applied to diverse social relationships such as first encounters, short-term acquaintances, friendships, relationships between working group members, educational or therapeutic settings, romantic relationships and family relationships. It has important consequences for how we conceptualize, understand, and investigate personality and social relationships. Copyright (C) 2011 John Wiley & Sons, Ltd.
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Commentators generally found our exposition of the concept of heritability helpful for psychologists, suggesting that we largely accomplished our primary goal. Many provided supplemental and helpful perspectives on concepts we addressed. A few of the comments indicated that we may not have been completely successful in making clear our secondary goal, which was to outline how heritability estimates confound a plethora of influences. In this response, we thus emphasize that we do not claim that specific kinds of complexity, or, even worse, intractable complexity, pervade the genetics of behavioural traits. Rather, our claim is that genetics is riddled with complexity of many degrees and kinds, and heritability is a poor indicator of either degree or kind of underlying genetic complexity. Copyright (C) 2011 John Wiley & Sons, Ltd.
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Genetic influences on behavioural traits are ubiquitous. When behaviourism was the dominant paradigm in psychology, demonstrations of heritability of behavioural and psychological constructs provided important evidence of its limitations. Now that genetic influences on behavioural traits are generally accepted, we need to recognise the limitations of heritability as an indicator of both the aetiology and likelihood of discovering molecular genetic associations with behavioural traits. We review those limitations and conclude that quantitative genetics and genetically informative research designs are still critical to understanding the roles of gene-environment interplay in developmental processes, though not necessarily in the ways commonly discussed. Copyright (C) 2011 John Wiley & Sons, Ltd.
