Behaviour genetics

The propensity to take risk underpins a wide variety of decision-making behavior, ranging from common ones such as asking for directions and trying out a new restaurant to more substantial economic decisions involving, for instance, one's investment or career. Despite the fundamental role of risk attitude in the economy, its genetic basis remains unknown. Using an experimental economics protocol combined with a classical twin strategy, we provide the first direct evidence of the heritability of economic risk attitude, at 57%. We do not find a significant role for shared environmental effects, a common observation in behavioral genetics that is contrary to commonly held views in economics. Our findings complement recent neuroeconomic studies in enhancing the understanding of the neurobiological basis of risk taking.

When hen the first author wrote the introductory chapter of Sociobiological ctives Perspectives on Human Development (MacDonald, 1988a), the basic llllllllllll approach was to attempt to integrate evolutionary thinking with prominent strands of theory already influential in developmental psychologyparticularly social learning theory, cognitive developmental theory, behavior genetics, and ethology. The intent was not to provide an alternative to these theoretical contributions, but to show how the revolution in evolutionary thinking inaugurated by William Hamilton, Robert Trivers, and G. C Williams and culminating in E. O. Wilson's (1975) Sociobiology could add richness and insight into many areas of developmental psychology.

The propensity to take risk underpins a wide variety of decision-making behavior, ranging from common ones such as asking for directions and trying out a new restaurant to more substantial economic decisions involving, for instance, one's investment or career. Despite the fundamental role of risk attitude in the economy, its genetic basis remains unknown. Using an experimental economics protocol combined with a classical twin strategy, we provide the first direct evidence of the heritability of economic risk attitude, at 57%. We do not find a significant role for shared environmental effects, a common observation in behavioral genetics that is contrary to commonly held views in economics. Our findings complement recent neuroeconomic studies in enhancing the understanding of the neurobiological basis of risk taking.

With the recent resurgence in popularity of trait theories of leadership, it is timely to consider the genetic determination of the multiple factors comprising the leadership construct. Individual differences in personality traits have been found to be moderately to highly heritable, and so it follows that if there are reliable personality trait differences between leaders and non-leaders, then there may be a heritable component to these individual differences. Despite this connection between leadership and personality traits, however, there are no studies of the genetic basis of leadership using modern behavior genetic methodology. The present study proposes to address the lack of research in this area by examining the heritability of leadership style, as measured by self-report psychometric inventories. The Multifactor Leadership Questionnaire (MLQ), the Leadership Ability Evaluation, and the Adjective Checklist were completed by 247 adult twin pairs (183 monozygotic and 64 same-s...

Objectives We argue that research in the psychological sciences testing evolutionarily informed questions could benefit considerably from more frequent use of techniques common in behavior genetics. Methods We review some of the reasons why data and analytical strategies in behavior genetics confer certain advantages over more traditional forms of data analysis. In particular, we focus on the wide availability of secondary data, the generalizability of data, the capacity of certain designs to bolster causal inference capabilities, and the overall adaptability of the research designs to a wide array of empirical questions. Results Not only do we show how the use of sibling designs can be of methodological assistance, but we also demonstrate how they can play a role in refining theories informed by evolution. In order to give a more concrete vision of what this can look like, we offer a type of case study using prior work which has already taken advantage of behavior genetic tools. Conclusions Because of the efforts to situate psychological science in the context of evolutionary biology, the field has undergone considerable intellectual growth. We suggest that by simply making more frequent use of tools in behavior genetics, the fields of psychology might further accelerate the progress that is already well underway.

The dispersal and migration of organisms have resulted in the colonisation of nearly every possible habitat and ultimately the extraordinary diversity of life. Animal dispersal tendencies are commonly heterogeneous (e.g. long vs. short) and non-random suggesting that phenotypic and genotypic variability between individuals can contribute to population-level heterogeneity in dispersal. Using laboratory and field experiments, we demonstrate that natural allelic variation in a gene underlying a foraging polymorphism in larval fruit flies (for), also influences their dispersal tendencies as adults. Rover flies (for R ; higher foraging activity) have consistently greater dispersal tendencies and are more likely to disperse longer distances than sitter flies (for s ; lower foraging activity). Increasing for expression in the brain and nervous system increases dispersal in sitter flies. Our study supports the notion that variation in dispersal can be driven by intrinsic variation in food-dependent search behaviours and confirms that single gene pleiotropic effects can contribute to population-level heterogeneity in dispersal.

The propensity to take risk underpins a wide variety of decision-making behavior, ranging from common ones such as asking for directions and trying out a new restaurant to more substantial economic decisions involving, for instance, one's investment or career. Despite the fundamental role of risk attitude in the economy, its genetic basis remains unknown. Using an experimental economics protocol combined with a classical twin strategy, we provide the first direct evidence of the heritability of economic risk attitude, at 57%. We do not find a significant role for shared environmental effects, a common observation in behavioral genetics that is contrary to commonly held views in economics. Our findings complement recent neuroeconomic studies in enhancing the understanding of the neurobiological basis of risk taking.

The study of inbred strains of rodents that differ for specific behaviours can help us to understand the biological mechanisms underlying complex psychological traits. Lewis (LEW) and SHR inbred rat strains, for example, have been recently proposed as a genetic model for the study of anxiety. Our goal was to characterise two Brazilian substrains of LEW and SHR rats, that have never been compared before, behaviourally and/or pharmacologically, in order to evaluate their potential contribution to studies on anxiety and pain. Male and female LEW and SHR rats were submitted after 8 weeks of age to five anxiety/emotionality tests: the open field (7 or 260 lux), the elevated plus-maze, the elevated T-maze and the black/white box. Rats of all groups were also submitted to the formalin test of nociception and measurement of blood pressure. Significant strain differences (P B 0.05) were observed in both sexes for all indices of anxiety and also for measures of pain and blood pressure. SHRs, compared with LEWs, explored more the aversive environments of all anxiety tests, showed less nociceptive responses and were hypertensive. All differences in experimental anxiety parameters agree with previous differences reported between two French LEW and SHR substrains, suggesting that LEWs are more anxious than SHRs, thus consolidating these strains as a useful genetic model for the study of anxiety and pain. The possible involvement of tachykinergic mechanisms is discussed.

Evolutionary psychology has seen the majority of its success exploring adaptive features of the mind believed to be ubiquitous across our species. This has given rise to the belief that the adaptationist approach has little to offer the field of differential psychology, which concerns itself exclusively with the ways in which individuals systematically differ. By framing the historical origins of both disciplines, and exploring the means through which they each address the unique challenges of psychological description and explanation, the present article identifies the conceptual and theoretical problems that have kept differential psychology isolated not only from evolutionary psychology, but from explanatory approaches in general. Paying special attention to these conceptual problems, the authors review how these difficulties are being overcome by contemporary evolutionary research, and offer instructive suggestions concerning how differential researchers (and others) can best build upon these innovations.

The target paper demonstrates the value of evolutionary genetics for personality research. Apart from a summing-up of concepts, the authors validate their theory with evidence from studies on both human- and animal personality. In this commentary, I want to show the need for inter-disciplinary research to answer questions on personality in psychology and biology.

Penke et al. (this issue) state that there are no studies of inbreeding depression on personality. In this response to their paper, we look at the effect of parents being born in the same geographical region on personality in themselves and in their offspring. Results show that when parents come from the same region, both they and their offspring score lower on sensation seeking than when parents come from different regions. These results may suggest effects of inbreeding depression on personality.

The dispersal and migration of organisms have resulted in the colonisation of nearly every possible habitat and ultimately the extraordinary diversity of life. Animal dispersal tendencies are commonly heterogeneous (e.g. long vs. short) and non-random suggesting that phenotypic and genotypic variability between individuals can contribute to population-level heterogeneity in dispersal. Using laboratory and field experiments, we demonstrate that natural allelic variation in a gene underlying a foraging polymorphism in larval fruit flies (for), also influences their dispersal tendencies as adults. Rover flies (for R ; higher foraging activity) have consistently greater dispersal tendencies and are more likely to disperse longer distances than sitter flies (for s ; lower foraging activity). Increasing for expression in the brain and nervous system increases dispersal in sitter flies. Our study supports the notion that variation in dispersal can be driven by intrinsic variation in food-dependent search behaviours and confirms that single gene pleiotropic effects can contribute to population-level heterogeneity in dispersal.

The scientific study of human behavior from a modern evolutionary perspective began in the 20th century with disciplines such as human ethology and behavioral ecology as well as sociobiology. This early work focused on the characterization of a universal human nature that could be observed across all societies and cultures, one believed to have emerged in part from evolutionary processes. With the passage of time a newer evolutionary discipline, evolutionary psychology, emerged in the early 1990 s and quickly flourished. The focus on human nature was retained from its forerunners, but the primary focus of the field underwent a decided shift. Gone was the emphasis on observable behaviors and in its place moved psychological and cognitive functioning. At the same time, the new field took an interesting departure from other branches of psychology by largely relegating the significance of individual differences across cognitive and personality styles (whether heritable or environmental in origin) to a minor role. In this paper, we review the primary original arguments for minimizing or ignoring the importance of individual differences in personality and cognition, all in the service of making the case that the study of human nature, and evolutionary psychology more generally, is not at odds with individual differences research. The two fields have always been complementary, with one serving as a frequent source of insight for the other.

Evolutionary psychology has seen the majority of its success exploring adaptive features of the mind believed to be ubiquitous across our species. This has given rise to the belief that the adaptationist approach has little to offer the field of differential psychology, which concerns itself exclusively with the ways in which individuals systematically differ. By framing the historical origins of both disciplines, and exploring the means through which they each address the unique challenges of psychological description and explanation, the present article identifies the conceptual and theoretical problems that have kept differential psychology isolated not only from evolutionary psychology, but from explanatory approaches in general. Paying special attention to these conceptual problems, the authors review how these difficulties are being overcome by contemporary evolutionary research, and offer instructive suggestions concerning how differential researchers (and others) can best build upon these innovations.

Early literacy and language skills of twin children in the USA, Australia, and Scandinavia were explored in a genetically sensitive design (maximum N = 615 pairs). For this article, we report aspects of preschool and Grade 2 data. In Grade 2, there were strong genetic influences on word reading, reading comprehension, and spelling. Vocabulary was about equally affected by genes and shared environment. Multivariate analyses indicated substantial genetic overlap among the Grade 2 literacy variables. Longitudinal analyses showed that genetic factors evident at the preschool stage continued to affect literacy and vocabulary three years later in Grade 2, but there was also evidence of new genetic factors coming into play over the time interval, at least for literacy. Suggestions are made about the search for underlying biological and cognitive processes, and educational implications are explored.

We review research on the ultimate and proximate origins of variation along the extraversion continuum. After describing the cost-benefit tradeoffs that may have maintained variation in extraversion over human evolution, we consider the evidence bearing on multiple distinct evolutionary hypotheses regarding the causal underpinnings of such variation. On the basis of the reviewed evidence, we argue that fluctuating selection on specific polymorphic genotypes is unlikely to explain the origins of individual differences in extraversion. Rather, adaptively patterned variation in extraversion is likely orchestrated primarily by facultative adaptations designed to calibrate behavioral strategies to cues available in ontogeny. For example, emerging research supports the hypothesis that extraversion may be ''reactively heritable'' by virtue of its calibration to heritable condition-dependent phenotypic features-which in turn helps explain extraversion's genetic variance, as well as its consistent positive association with reproductive success. Finally, evidence suggests that some of the inter-individual variance in extraversion is fundamentally noisy, arising as a side effect of mutation-selection balance or pleiotropic polymorphisms maintained via pathogen-host coevolution. If correct, these conclusions indicate that future research should focus on elucidating the facultative adaptations designed to regulate the production of behaviors falling on the extraversion continuum.

The dispersal and migration of organisms have resulted in the colonisation of nearly every possible habitat and ultimately the extraordinary diversity of life. Animal dispersal tendencies are commonly heterogeneous (e.g. long vs. short) and non-random suggesting that phenotypic and genotypic variability between individuals can contribute to population-level heterogeneity in dispersal. Using laboratory and field experiments, we demonstrate that natural allelic variation in a gene underlying a foraging polymorphism in larval fruit flies (for), also influences their dispersal tendencies as adults. Rover flies (for R ; higher foraging activity) have consistently greater dispersal tendencies and are more likely to disperse longer distances than sitter flies (for s ; lower foraging activity). Increasing for expression in the brain and nervous system increases dispersal in sitter flies. Our study supports the notion that variation in dispersal can be driven by intrinsic variation in food-dependent search behaviours and confirms that single gene pleiotropic effects can contribute to population-level heterogeneity in dispersal.

Personality traits are basicdimensions of behavioral variation, and twin, family, and adoption studies show that around 30% of the between-individual variation is due to genetic variation. There is rapidly growing interest in understanding the evolutionary basis of this genetic variation. Several evolutionary mechanisms could explain how genetic variation is maintained in traits, and each of these makes predictions in terms of the relative contribution of rare and common genetic variants to personality variation, the magnitude of nonadditive genetic influences, and whether personality is affected by inbreeding. Using genomewide single nucleotide polymorphism (SNP) data from > 8000 individuals, we estimated that little variation in the Cloninger personality dimensions (7.2% on average) is due to the combined effect of common, additive genetic variants across the genome, suggesting that most heritable variation in personality is due to rare variant effects and/or a combination of dominance and epistasis. Furthermore, higher levels of inbreeding were associated with less socially desirable personality trait levels in three of the four personality dimensions. These findings are consistent with genetic variation in personality traits having been maintained by mutation-selection balance.

Teaching evolutionary principles in higher education can provide an integrative theoretical foundation that can be used to incorporate vast amounts of interdisciplinary knowledge. Yet, paradoxes regarding evolutionary theory's place in academia are rampant—particularly when it comes to applying evolutionary principles to psychology. The EvoS Consortium is premised on the idea that evolutionary theory can shed light on phenomena across all areas of academia. Evolutionary principles have been an important aspect in the advancement of scientific research and knowledge since the modern synthesis in the late 1930's. In an effort to demonstrate the utility of the evolutionary perspective throughout psychology as a whole, this paper includes sections on several of the major areas of psychology. Specifically, we use this approach to address social, personality, developmental, cultural, biological and applied psychology. Very basically, this paper is designed to show how evolutionary...

Early literacy and language skills of twin children in the USA, Australia, and Scandinavia were explored in a genetically sensitive design (maximum N = 615 pairs). For this article, we report aspects of preschool and Grade 2 data. In Grade 2, there were strong genetic influences on word reading, reading comprehension, and spelling. Vocabulary was about equally affected by genes and shared environment. Multivariate analyses indicated substantial genetic overlap among the Grade 2 literacy variables. Longitudinal analyses showed that genetic factors evident at the preschool stage continued to affect literacy and vocabulary three years later in Grade 2, but there was also evidence of new genetic factors coming into play over the time interval, at least for literacy. Suggestions are made about the search for underlying biological and cognitive processes, and educational implications are explored.

Penke et al. (this issue) state that there are no studies of inbreeding depression on personality. In this response to their paper, we look at the effect of parents being born in the same geographical region on personality in themselves and in their offspring. Results show that when parents come from the same region, both they and their offspring score lower on sensation seeking than when parents come from different regions. These results may suggest effects of inbreeding depression on personality.

Concepts are linguistic structures with specific syntax and semantics used as sources of communicating ideas. Concepts can be simple (e.g., tree), complex (e.g., adaptation). The conceptual interrelationships and some evolutionary consequences upon which these interrelations are based will be addressed here. The evolutionary ecology is an area of research from the population evolutionary biology that deals mainly with the effect of positive natural selection on panmictic and structured populations. Environmental factors, conditions and variable resources in time and space, constitute the selective agents that act on the phenotypic and genotypic variation of populations in a single generation, could result in evolutionary adaptations, which are simply those traits that are most likely to confer survival and reproduction (evolutionary fitness) of the phenotypes that carry them in successive generations. The bases of adaptation are mainly genetic and transmitted vertically or horizontally. The phenotypic variance of the population is a conjoint consequence of the additive genotypic variance (heritability), nonadditive variance (dominance and epistasis), pleiotropy and the interaction between genotype and environment. The ability of the same genotype to respond to spatial environmental variations can result in phenotypic plasticity that manifests itself through reaction norms. The total phenotypic variation and its genetic and environmental components influence the ability of a population to evolve (evolvability).

We respond to Gallup’s (2020) opinion piece by indicating that psychologists have yet to agree on an operationalized definition of  “intelligence.” We offer our understanding of the literature that a decline of human intelligence is mixed; additionally, if a decline in human intelligence was supported, evolutionary scholars are not in a position to change the course of such decline. We clarify what evolutionary psychology is: the study of human nature by empirical examination of evidence for adaptive design hypotheses, but not a mission to preach and solve problems associated with evolutionary challenges. Finally, we dispute Gallup’s (2020) suggested proscription for evolutionary psychologists.

Extreme personality traits in humans often have detrimental life consequences, so they have long been supposed to be diseases. However, many other species display personality variants that are maintained due to their fitness advantages; in this case, they are construed as strategies. To examine the fitness costs and benefits of pathological personality traits in humans, we measured features of the A (socially odd, distrustful), B (incentive-seeking, selfish) and C (fearful, inhibited) clusters with the Personality Diagnostic Questionnaire-4+ (PDQ-4+) in a sample of 738 outpatients. Fitness relevant parameters like mating success, reproductive output, self preservation, and access to status were assessed with the Life Outcome Questionnaire. No fitness advantages were found for high-A subjects. In contrast, high-B subjects tripled low-B subjects with regard to mating success and had 39% more offspring. Further, high-C subjects outperformed low-C subjects in attaining status and avoiding risks. These findings help explain the commonness of some extreme personality traits in humans, and suggest that they should be seen as evolutionary strategies rather than as diseases.

The aim of this paper is to examine the sources and structure of covariation between disordered eating, neuroticism, parental care and protection, self-esteem and emotional reliance on other people. The eating, personality and family functioning measures, obtained from 537 MZ and 344 DZ female twin pairs aged 30±45 years, were examined using multivariate biometrical genetic modeling techniques. The best-®tting independent pathway model suggested that the measure of disordered eating shared unique environmental risk factors with neuroticism and perceptions of parental care. Neuroticism, selfesteem and emotional reliance on others shared genetic risk factors. The speci®c sources of individual variation for the six variables included a mixture of: (a) genetic, common and unique environment (disordered eating and the parental perception variables), (b) genetic and unique environment (neuroticism) and (c) unique environment only (self-esteem and emotional reliance on others). Disordered eating did not share genetic risk factors with any of the measured variables. The implications of these ®ndings for our understanding of disordered eating are discussed. #

Integration with evolutionary theory could enhance personality theory by generating original predictions about the mechanisms governing personality. Novel hypotheses about how personality works can be derived from theories about the ultimate function of personality traits. Personality psychology currently describes and explains how personality is structured and how the mechanisms that produce such differences in behavioural patterns work. Personality theorists observe how personality differences develop and explain the proximate ('how

Substance P (SP) is involved in the pathophysiology of several psychiatric disorders and is considered a central stress neurotransmitter. Endoge-nous SP does not inhibit the initial extent of the HPA axis response to restraint stress, but reduces the duration of the stress suggesting that SP plays an important role in the transition between acute and chronic stress. Stress hormones can alter metabolic functions in white adipose tissue and liver. The HPA axis is the endocrine pathway that promotes lipolysis elevating free fatty acid levels (FFA) in blood, besides indirectly causing hyperglycemia. In the present study, changes in the blood levels of stress markers in the anxiogenic-like effects of SP, as evaluated on the elevated plus-maze (EPM), were studied in adult male rats. Serum corticosterone was used as the traditional stress marker, while the plasma FFA and glucose were used as alternative anxiety/stress markers. Our findings show: (a) elevated corticosterone levels, confirming the aversive situation induced by SP (behaviorally assessed in the EPM) and indicating SP as a " chemical " stressor; (b) elevated levels of FFA and glucose, indicators of stress-induced mobilization of energy substrates, confirming the stressor effect of SP; (c) FFA levels can be used as an accurate, sensitive and reliable index of acute stress situations, including in the anxiogenic-like effect of SP, with the FFA response being as good as corticosterone as a stress marker in this case; (d) NK1 receptors involvement in the underlying mechanisms of the behavioral and metabolic effects of SP. Finally, our study indicates that some of these physiological variables are positively related to the stressor intensity.

How do populations respond to environmental change? We aim to provide a conceptual overview using the Price equation, which decomposes the mean change exhibited by a population into four components: viability selection, within-individual changes over their lifetime, fecundity selection, and parent-offspring differences. Mechanisms such as phenotypic plasticity, learning, genetic adaptation, maternal effects and cultural evolution can all be understood via their infl uences on these components. However, we also highlight the fact that population size effects should often be considered more explicitly than this breakdown of components achieves. For example, phenotypic plasticity may help or hinder adaptive evolution, and adaptation does not necessarily lead to a better maintenance of large population size.

The use of the behavioural repertoire approach in comparative personality research involves the compilation of an ethogram. However, what behaviours should be included in the ethogram and whether they should be grouped into categories is unclear. To ensure that the behaviours belong to the natural repertoire of the species, certain assumptions regarding their underlying mechanisms are necessary. The selection of behaviours from which personality traits can be derived should take into account the notion that individuals with different personalities may seek out different stimuli and actively shape their own environment.

Substance P (SP) is involved in the pathophysiology of several psychiatric disorders and is considered a central stress neurotransmitter. Endogenous SP does not inhibit the initial extent of the HPA axis response to restraint stress, but reduces the duration of the stress suggesting that SP plays an important role in the transition between acute and chronic stress. Stress hormones can alter metabolic functions in white adipose tissue and liver. The HPA axis is the endocrine pathway that promotes lipolysis elevating free fatty acid levels (FFA) in blood, besides indirectly causing hyperglycemia. In the present study, changes in the blood levels of stress markers in the anxiogenic-like effects of SP, as evaluated on the elevated plus-maze (EPM), were studied in adult male rats. Serum corticosterone was used as the traditional stress marker, while the plasma FFA and glucose were used as alternative anxiety/stress markers. Our findings show: (a) elevated corticosterone levels, confirming the aversive situation induced by SP (behaviorally assessed in the EPM) and indicating SP as a "chemical" stressor; (b) elevated levels of FFA and glucose, indicators of stress-induced mobilization of energy substrates, confirming the stressor effect of SP; (c) FFA levels can be used as an accurate, sensitive and reliable index of acute stress situations, including in the anxiogenic-like effect of SP, with the FFA response being as good as corticosterone as a stress marker in this case; (d) NK1 receptors involvement in the underlying mechanisms of the behavioral and metabolic effects of SP. Finally, our study indicates that some of these physiological variables are positively related to the stressor intensity.

This article provides the first test of an adaptationist 'common calibration' theory to explain the origins of trait covariation, which holds that (i) personality traits are often facultatively calibrated in response to cues that ancestrally predicted the reproductive payoffs of different trait levels and (ii) distinct traits that are calibrated on the basis of common input cues will exhibit consistent patterns of covariation. This theory is applied to explain the covariation within a 'personality syndrome' encompassing various interpersonal trait dimensions (e.g. extraversion, emotionality and attachment styles). Specifically, it is hypothesized that these traits are inter-correlated because each is calibrated in response to relative bargaining power (RBP)-a joint function of one's ability to benefit others and harm others. Path analyses from a correlational study compellingly supported this theoretical model: Objective and self-perceived measures of RBP-enhancing phenotypic features (physical attractiveness and physical strength) influenced an internal regulatory variable indexing RBP (i.e. self-perceived RBP), which in turn had robust effects on each of the focal personality traits. Moreover, in support of the theory's core postulate, controlling for selfperceived RBP greatly reduced the covariation within the interpersonal syndrome. These novel findings illustrate the promise of an evolutionary psychological approach to elucidating trait covariation.

Traits that are attractive to the opposite sex are often positively correlated when scaled such that scores increase with attractiveness, and this correlation typically has a genetic component. Such traits can be genetically correlated due to genes that affect both traits ("pleiotropy") and/or because assortative mating causes statistical correlations to develop between selected alleles across the traits ("gametic phase disequilibrium"). In this study, we modeled the covariation between monozygotic and dizygotic twins, their siblings, and their parents (total N = 7,905) to elucidate the nature of the correlation between two potentially sexually selected traits in humans: height and IQ. Unlike previous designs used to investigate the nature of the height-IQ correlation, the present design accounts for the effects of assortative mating and provides much less biased estimates of additive genetic, non-additive genetic, and shared environmental influences. Both traits...

To search for genetic influence on human fertility differentials appears inconsistent with past empirical research and prior interpretations of Fisher's fundamental theorem of natural selection. We discuss Fisher's theorem and give reasons why genetic influences may indeed account for individual differences in human fertility. We review recent empirical studies showing genetic influence on variance in fertility outcomes and precursors to fertility. Further, some of the genetic variance underlying fertility outcomes overlaps with that underlying fertility precursors. Findings from different cultures, different times, different levels of data, and both behavioral and molecular genetic designs lead to the same conclusion: Fertility differentials are genetically influenced, and at least part of the influence derives from behavioral precursors that are under volitional control, which are themselves genetically mediated.

When hen the first author wrote the introductory chapter of Sociobiological ctives Perspectives on Human Development , the basic llllllllllll approach was to attempt to integrate evolutionary thinking with prominent strands of theory already influential in developmental psychologyparticularly social learning theory, cognitive developmental theory, behavior genetics, and ethology. The intent was not to provide an alternative to these theoretical contributions, but to show how the revolution in evolutionary thinking inaugurated by William Hamilton, Robert Trivers, and G. C Williams and culminating in E. O. Sociobiology could add richness and insight into many areas of developmental psychology.

A central theme of the flood of literature in recent years in "evolutionary psychology" and "behavioral genetics" is that much or even most human behavior has been programmed into the human genome by natural selection. We show that this conclusion is without basis. Evolutionary psychology is a series of "just-so" stories rooted in part in the erroneous notion that human beings during the Pleistocene all lived in the same environment of evolutionary adaptation. Behavioral genetics is based on a confusion of the information contained in a technical statistic called "heritability" with the colloquial meaning of the term, exacerbated by oversimplification of statistical models for the behavioral similarity of twins. In fact, information from twin studies, cross-fostering, sexual behavior, and the Human Genome Project makes it abundantly clear that most interesting aspects of the human behavioral phenome are programmed into the brain by the environment. The general confusion created by the genetic determinists has had and will continue to have unfortunate effects on public policy.

The study of inbred strains of rodents that differ for specific behaviours can help us to understand the biological mechanisms underlying complex psychological traits. Lewis (LEW) and SHR inbred rat strains, for example, have been recently proposed as a genetic model for the study of anxiety. Our goal was to characterise two Brazilian substrains of LEW and SHR rats, that have never been compared before, behaviourally and/or pharmacologically, in order to evaluate their potential contribution to studies on anxiety and pain. Male and female LEW and SHR rats were submitted after 8 weeks of age to five anxiety/emotionality tests: the open field (7 or 260 lux), the elevated plus-maze, the elevated T-maze and the black/white box. Rats of all groups were also submitted to the formalin test of nociception and measurement of blood pressure. Significant strain differences (P B 0.05) were observed in both sexes for all indices of anxiety and also for measures of pain and blood pressure. SHRs, compared with LEWs, explored more the aversive environments of all anxiety tests, showed less nociceptive responses and were hypertensive. All differences in experimental anxiety parameters agree with previous differences reported between two French LEW and SHR substrains, suggesting that LEWs are more anxious than SHRs, thus consolidating these strains as a useful genetic model for the study of anxiety and pain. The possible involvement of tachykinergic mechanisms is discussed.

Many consider the maintenance of heritable behavioral variability among individuals across evolutionary time a dilemma for evolutionary psychology. Why have natural and sexual selection not eliminated individual differences in favor of some optimally adaptive set of universal trait values? The statistical associations among personality traits and a wide array of life outcomes clearly relevant to survival and reproduction make it unlikely that such individual differences in traits could be selectively neutral. A principled application of quantitative theoretical ecology explains inter-individual behavioral diversity and how the diversification of behavioral phenotypes matches the diversification of socioecological niches within species-typical multidimensional niche space, particularly for social species. These selective pressures maintain and, in some cases, increase individual trait differences during both developmental and evolutionary time. Individual variation in personality is shaped by multiple selective pressures, including: (1) frequency-dependent niche-splitting, (2) developmental plasticity, (3) genetic diversification, directional social selection, and (5) behavioral flexibility.

Numerous arguments have addressed the controversies surrounding the category of emotional disturbance (ED) and the exclusion, or proposed inclusion, of students with social maladjustment (SM). In this article we address the consensually agreed upon characteristics of ED that are in common with SM, in addition to examining characteristics that supposedly also differentiate students who are ED from those who are SM. Given that SM has not been clearly defined and therefore it has proven to be an exceedingly difficult task for practitioners to differentiate children who are ED from SM suggests that they should be considered as a single condition termed ED/SM. Characteristics of ED and SM have substantial overlap, but apparently enough difference is noted to argue that they are distinguishable disorders requiring differential diagnoses and treatment, resulting in one that warrants special education services, and one that does not. We argue that whether these children are classified as ED, SM, or ED/SM, they all should qualify for special education services based primarily on the inescapable fact that they need professional assistance if their condition militates against optimal educational attainment. Furthermore, there exists little, if any, differentiation of effective and enduring treatment on the basis of whether a child is classified as either ED or SM. Finally, an alternative nonenvironmental explanation is offered for the apparent increase in incidence of characteristics associated with ED/SM. The alternative explanation is based on the genetic phenomenon heterosis that provides a plausible argument that secular changes in several cognitive, physical, and psychological characteristics may have the same nonenvironmental etiology. © 2004 Wiley Periodicals, Inc. Psychol Schs 41: 861–865, 2004.

The use of the behavioural repertoire approach in comparative personality research involves the compilation of an ethogram. However, what behaviours should be included in the ethogram and whether they should be grouped into categories is unclear. To ensure that the behaviours belong to the natural repertoire of the species, certain assumptions regarding their underlying mechanisms are necessary. The selection of behaviours from which personality traits can be derived should take into account the notion that individuals with different personalities may seek out different stimuli and actively shape their own environment.

A genomic region neighboring the a-synuclein gene, on rat chromosome 4, has been associated with anxiety-and alcohol-related behaviors in different rat strains. In this study, we have investigated potential molecular and physiological links between a-synuclein and the behavioral differences observed between Lewis (LEW) and Spontaneously Hypertensive (SHR) inbred rats, a genetic model of anxiety. As expected, LEW rats appeared more fearful than SHR rats in three anxiety models: open field, elevated plus maze and light/dark box. Moreover, LEW rats displayed a higher preference for alcohol and consumed higher quantities of alcohol than SHR rats. a-Synuclein mRNA and protein concentrations were higher in the hippocampus, but not the hypothalamus of LEW rats. This result inversely correlated with differences in dopamine turnover in the hippocampus of LEW and SHR rats, supporting the hypothesis that a-synuclein is important in the downregulation of dopamine neurotransmission. A novel single nucleotide polymorphism was identified in the 3 0 -untranslated region (3 0 -UTR) of the asynuclein cDNA between these two rat strains. Plasmid constructs based on the LEW 3 0 -UTR sequence displayed increased expression of a reporter gene in transiently transfected PC12 cells, in accordance with in-vivo findings, suggesting that this nucleotide exchange might participate in the differential expression of a-synuclein between LEW and SHR rats. These results are consistent with a novel role for a-synuclein in modulating rat anxiety-like behaviors, possibly through dopaminergic mechanisms. Since the behavioral and genetic differences between these two strains are the product of independent evolutionary histories, the possibility that polymorphisms in the a-synuclein gene may be associated with vulnerability to anxiety-related disorders in humans requires further investigation.

Most evolutionary psychologists share a belief in one key concept: the environment of evolutionary adaptedness (EEA), i.e., the ancestral environment that shaped the heritable mental and behavioral traits of present-day humans. It is usually placed in the African savannah of the Pleistocene, long before our ancestors began to spread to other continents some fifty thousand years ago. Thus, later environments have not given rise to new traits through genetic evolution.

This belief rests on two arguments: 1) such traits are complex and therefore evolve too slowly to have substantially changed over the past fifty thousand years; 2) because the same time frame has seen our species diversify into many environments, recent traits should tend to be environment-specific and hence population-specific, yet such specificity seems inconsistent with the high genetic overlap among human populations. Both arguments are weaker than they seem. New complex traits can arise over a relatively short time through additions, deletions, or modifications to existing complex traits, and genetic overlap can be considerable even between species that are morphologically, behaviorally, and physiologically distinct.

There is thus no conceptual barrier to the existence of EEAs in post-Pleistocene times. Such a paradigm could shed light on such research topics as the visual word form area, reproductive strategy, predisposition to violence among young men, and personality traits. Eventually, a multi-EEA model may dominate evolutionary psychology, perhaps after an interim period of accommodation with the current model.

The study of inbred strains of rodents that differ for specific behaviours can help us to understand the biological mechanisms underlying complex psychological traits. Lewis (LEW) and SHR inbred rat strains, for example, have been recently proposed as a genetic model for the study of anxiety. Our goal was to characterise two Brazilian substrains of LEW and SHR rats, that have never been compared before, behaviourally and/or pharmacologically, in order to evaluate their potential contribution to studies on anxiety and pain. Male and female LEW and SHR rats were submitted after 8 weeks of age to five anxiety/emotionality tests: the open field (7 or 260 lux), the elevated plus-maze, the elevated T-maze and the black/white box. Rats of all groups were also submitted to the formalin test of nociception and measurement of blood pressure. Significant strain differences (P B 0.05) were observed in both sexes for all indices of anxiety and also for measures of pain and blood pressure. SHRs, compared with LEWs, explored more the aversive environments of all anxiety tests, showed less nociceptive responses and were hypertensive. All differences in experimental anxiety parameters agree with previous differences reported between two French LEW and SHR substrains, suggesting that LEWs are more anxious than SHRs, thus consolidating these strains as a useful genetic model for the study of anxiety and pain. The possible involvement of tachykinergic mechanisms is discussed.

The use of the behavioural repertoire approach in comparative personality research involves the compilation of an ethogram. However, what behaviours should be included in the ethogram and whether they should be grouped into categories is unclear. To ensure that the behaviours belong to the natural repertoire of the species, certain assumptions regarding their underlying mechanisms are necessary. The selection of behaviours from which personality traits can be derived should take into account the notion that individuals with different personalities may seek out different stimuli and actively shape their own environment.