Mittwoch, 30. Oktober 2013

Human Ability to Recognize Kin Visually Within Primates

Human Ability to Recognize Kin Visually Within Primates
Alexandra Avergne et al.; 2009
http://link.springer.com/article/10.1007/s10764-009-9339-0/fulltext.html


Abstract

The assessment of relatedness is a key determinant in the evolution of social behavior in primates. Humans are able to detect kin visually in their own species using facial phenotypes, and facial resemblance in turn influences both prosocial behaviors and mating decisions. This suggests that cognitive abilities that allow facial kin detection in conspecifics have been favored in the species by kin selection. We investigated the extent to which humans are able to recognize kin visually by asking human judges to assess facial resemblance in 4 other primate species (common chimpanzees, western lowland gorillas, mandrills, and chacma baboons) on the basis of pictures of faces. Humans achieved facial interspecific kin recognition in all species except baboons. Facial resemblance is a reliable indicator of relatedness in at least chimpanzees, gorillas, and mandrills, and future work should explore if the primates themselves also share the ability to detect kin facially.

Low fertility increases descendant socioeconomic position but reduces long-term fitness in a modern post-industrial society

Low fertility increases descendant socioeconomic position but reduces long-term fitness in a modern post-industrial society
Anna Goodman et al.; 2012


Abstract

Adaptive accounts of modern low human fertility argue that small family size maximises the inheritance of socioeconomic resources across generations and may consequently increase long-term fitness. This paper explores the long-term impacts of fertility and socioeconomic position (SEP) on multiple dimensions of descendant success in a unique Swedish cohort of 14,000 individuals born 1915-1929. We show that low fertility and high SEP predict increased descendant socioeconomic success across four generations. Furthermore, these effects are multiplicative, with the greatest benefits of low fertility observed when SEP is high. Low fertility and high SEP do not, however, predict increased descendant reproductive success. Our results are therefore consistent with the idea that modern fertility limitation represents a strategic response to the local costs of rearing socioeconomically competitive offspring, but contradict adaptive models suggesting that it maximises long-term fitness. This indicates a conflict in modern societies between behaviours promoting socioeconomic versus biological success. This paper also makes a methodological contribution, demonstrating that number of offspring strongly predicts long-term fitness and thereby validating use of fertility data to estimate current selective pressures in modern populations. Finally our findings highlight that differences in fertility and SEP have important long-term effects on the persistence of social inequalities across generations.

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"We do, however, find strong support for the prediction that fertility limitation in modern societies enhances descendant socioeconomic success. Thus, our results indicate that reproductive behaviours that promote biological success (i.e. long-term genetic fitness) are in conflict with those that promote descendant socioeconomic success in modern populations. Specifically, we find that both low parental fertility and high parental SEP independently predict higher schoolmarks, educational level and income, and this is generally true in male and female descendants alike ... . Moreover, these associations persist up to at least the great-grandchild generation, reflecting the advantage of starting one’s own offspring on a favourable socioeconomic trajectory.
We also demonstrate for the first time a multigenerational interaction between SEP and fertility, such that the socioeconomic benefit of low fertility was especially large in groups that already had high SEP. This finding adds to a number of recent studies indicating that demographic modernization is associated with increased socioeconomic pay-offs to fertility limitation for the wealthiest families ... ."

Dienstag, 29. Oktober 2013

Attractive men induce testosterone and cortisol release in women

Attractive men induce testosterone and cortisol release in women
Hassan A Lopez et al.; 2009


Abstract

Recently, Roney et al. (Roney, J.R., Lukaszewski, A.W., Simmons, Z.L., 2007. Rapid endocrine responses of young men to social interactions with young women. Horm. Behav. 52, 326–33; Roney, J.R., Mahler, S.V., Maestripieri, D., 2003. Behavioral and hormonal responses of men to brief interactions with women. Evol. Hum. Behav. 24, 365–375) demonstrated that men release testosterone and cortisol in response to brief social interactions with young women. The current experiment examined whether women show a similar endocrine response to physically and behaviorally attractive men. 120 women (70 naturally-cycling and 50 using hormonal contraceptives) were shown one of four 20-minute video montages extracted from popular films, depicting the following scenarios: 1) an attractive man courting a young woman (experimental stimulus), 2) a nature documentary (video clip control), 3) an unattractive older man courting a woman (male control), and 4) an attractive woman with no men present (female control). Saliva samples were taken before and after presentation of the stimulus, and were later analyzed for testosterone and cortisol content via enzyme immunoassay. Naturally-cycling women experienced a significant increase in both testosterone and cortisol in response to the experimental stimulus but to none of the control stimuli. Participants taking hormonal contraceptives also showed a significant cortisol response to the attractive man. Women may release adrenal steroid hormones to facilitate courtship interactions with high mate-value men.

Testosterone responses to competition in men are related to facial masculinity

Testosterone responses to competition in men are related to facial masculinity
Nicholas Pound et al.; 2009
http://rspb.royalsocietypublishing.org/content/276/1654/153.full


Abstract

Relationships between androgens and the size of sexually dimorphic male traits have been demonstrated in several non-human species. It is often assumed that a similar relationship exists for human male faces, but clear evidence of an association between circulating testosterone levels and the size of masculine facial traits in adulthood is absent. Here we demonstrate that, after experimentally determined success in a competitive task, men with more a masculine facial structure show higher levels of circulating testosterone than men with less masculine faces. In participants randomly allocated to a ‘winning’ condition, testosterone was elevated relative to pre-task levels at 5 and 20 min post-task. In a control group of participants allocated to a ‘losing’ condition there were no significant differences between pre- and post-task testosterone. An index of facial masculinity based on the measurement of sexually dimorphic facial traits was not associated with pre-task (baseline) testosterone levels, but was associated with testosterone levels 5 and 20 min after success in the competitive task. These findings indicate that a man's facial structure may afford important information about the functioning of his endocrine system.

Behavioral and hormonal responses of men to brief interactions with women

Behavioral and hormonal responses of men to brief interactions with women
James R Roney et al.; 2003


Abstract

This study tested for behavioral and hormonal reactions of young men to brief social encounters with potential mating partners. Male college students were randomly assigned to engage in a short conversation with either a young man (male condition) or a young woman (female condition). Participants provided saliva samples before and after the conversation, completed a battery of psychological measures after the interaction, and had their behavior rated by their conversation partners. Salivary testosterone (T) increased significantly over baseline levels in the female condition only, though differences between conditions were not significant. In addition, change in T was significantly correlated with the degree to which the female confederates thought the male participants were trying to impress them. These behavioral ratings, in turn, were correlated with the participants’ ratings of the female confederates as potential romantic partners. Results were generally consistent with the hypothesis that human males may exhibit a behavioral and endocrine courtship response that is similar to that observed in males of many nonhuman vertebrate species.

Montag, 28. Oktober 2013

Cigarette Smoking and Age at Natural Menopause

Cigarette Smoking and Age at Natural Menopause
David W Kaufman et al.; 1980
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1619390/pdf/amjph00677-0086.pdf


Abstract

In a cohort of 656 naturally postmenopausal women who were interviewed at age 60 to 69 years, and who had reached their menopause between the ages of 35 and 59 years, the mean age at menopause declined with increasing number of cigarettes smoked, from 49.4 years of age among women who had never smoked to 47.6 years of age among women who smoked at least 15 cigarettes per day (p < 0.02). The relationship was not attributable to the onset of menopause inducing women to take up smoking.

Freitag, 25. Oktober 2013

How Does Racial Diversity Raise Income Inequality

How Does Racial Diversity Raise Income Inequality
Gerhard Meisenberg, 2008


Abstract

In international comparisons, a high level of racial diversity is associated with a high level of income inequality. One hypothesis proposes that racial diversity leads to increased variance in intellectual ability, which leads to increased income inequality presumably through the action of market forces. A second hypothesis proposes that racially diverse societies are more unequal because they have less social solidarity and less redistribution of wealth from the rich to the poor. The present study investigates the first hypothesis with the results of international school assessment programs (TIMSS and PISA). High racial diversity is found to be related to a greater ability spread on these assessments, but ability variance is not independently related to the Gini index. The second hypothesis is tested with a measure of “big government” that is derived from the economic freedom indices of the Fraser Institute and the Heritage Foundation. Big government is negatively related to both racial diversity and the Gini index.

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"If racial diversity favors income inequality, and if advanced postindustrial nations are becoming more diverse in the wake of replacement migration (Coleman, 2002), we can predict a continuing trend towards greater income inequality."

Montag, 21. Oktober 2013

Genetic Determinants of Financial Risk Taking

Genetic Determinants of Financial Risk Taking
Camelia M Kuhnen and Joan Y Chiao; 2009


Abstract

Individuals vary in their willingness to take financial risks. Here we show that variants of two genes that regulate dopamine and serotonin neurotransmission and have been previously linked to emotional behavior, anxiety and addiction (5-HTTLPR and DRD4) are significant determinants of risk taking in investment decisions. We find that the 5-HTTLPR s/s allele carriers take 28% less risk than those carrying the s/l or l/l alleles of the gene. DRD4 7-repeat allele carriers take 25% more risk than individuals without the 7-repeat allele. These findings contribute to the emerging literature on the genetic determinants of economic behavior.

The Genetics of Economic Risk Preferences

The Genetics of Economic Risk Preferences
Michael J Zyphur et al.; 2009


Abstract

We examine the influence of genetics on economic risk preferences by administering a measure of these preferences to monozygotic (MZ) (i.e., identical) and dizygotic (DZ) (i.e., non-identical) twin pairs. Our analysis supports a dominant genetic effect and virtually no additive genetic effect on economic risk preferences, with the heritability of preferences estimated at 0.63. These findings suggest that over half of the variation in such preferences can be explained by genetic factors, with the remainder of the variance explained by environmental influences not shared among sibling twins. We discuss the implications of our findings for the study of individual differences in economic risk preferences.

Is Beauty in the Face of the Beholder?

Is Beauty in the Face of the Beholder?
Bruno Laeng et al.; 2013


Abstract

Opposing forces influence assortative mating so that one seeks a similar mate while at the same time avoiding inbreeding with close relatives. Thus, mate choice may be a balancing of phenotypic similarity and dissimilarity between partners. In the present study, we assessed the role of resemblance to Self’s facial traits in judgments of physical attractiveness. Participants chose the most attractive face image of their romantic partner among several variants, where the faces were morphed so as to include only 22% of another face. Participants distinctly preferred a “Self-based morph” (i.e., their partner’s face with a small amount of Self’s face blended into it) to other morphed images. The Self-based morph was also preferred to the morph of their partner’s face blended with the partner’s same-sex “prototype”, although the latter face was (“objectively”) judged more attractive by other individuals. When ranking morphs differing in level of amalgamation (i.e., 11% vs. 22% vs. 33%) of another face, the 22% was chosen consistently as the preferred morph and, in particular, when Self was blended in the partner’s face. A forced-choice signal-detection paradigm showed that the effect of self-resemblance operated at an unconscious level, since the same participants were unable to detect the presence of their own faces in the above morphs. We concluded that individuals, if given the opportunity, seek to promote “positive assortment” for Self’s phenotype, especially when the level of similarity approaches an optimal point that is similar to Self without causing a conscious acknowledgment of the similarity.

Mutual Mate Choice: Sexual Selection Versus Sexual Conflict

Mutual Mate Choice: Sexual Selection Versus Sexual Conflict
Anne Campbell; Sep 2013
Psychological Inquiry

Sonntag, 20. Oktober 2013

Adaptations in humans for assessing physical strength from the voice

Adaptations in humans for assessing physical strength from the voice
Aaron Sell et al.; 2010
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2982226/


Abstract

Recent research has shown that humans, like many other animals, have a specialization for assessing fighting ability from visual cues. Because it is probable that the voice contains cues of strength and formidability that are not available visually, we predicted that selection has also equipped humans with the ability to estimate physical strength from the voice. We found that subjects accurately assessed upper-body strength in voices taken from eight samples across four distinct populations and language groups: the Tsimane of Bolivia, Andean herder-horticulturalists and United States and Romanian college students. Regardless of whether raters were told to assess height, weight, strength or fighting ability, they produced similar ratings that tracked upper-body strength independent of height and weight. Male voices were more accurately assessed than female voices, which is consistent with ethnographic data showing a greater tendency among males to engage in violent aggression. Raters extracted information about strength from the voice that was not supplied from visual cues, and were accurate with both familiar and unfamiliar languages. These results provide, to our knowledge, the first direct evidence that both men and women can accurately assess men's physical strength from the voice, and suggest that estimates of strength are used to assess fighting ability.

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  1. Average individual estimates of strength from the voice were accurate and highly significant across all six male samples ranging from γ = 0.18 to 31. This accuracy is similar to the accuracy of strength assessment from static visual images of the face, but lower than estimation from images of the body ().
  2. Accuracy of strength estimation was similar across both familiar and unfamiliar languages.
  3. While strength was accurately estimated from women's voices in both the US and Romanian samples, the effect was about half as large as for their male counterparts. The same pattern is found when assessing strength from visual images of the face ().
  4. Estimates of strength were notably enhanced when both auditory and visual channels were available (see below).
  5. Assessments of strength remained significant, controlling for both height and weight

Samstag, 19. Oktober 2013

All One Species?

http://westhunt.wordpress.com/2013/10/18/all-one-species-2/

Why Do Boys Engage in More Risk Taking Than Girls?

Why Do Boys Engage in More Risk Taking Than Girls? The Role of Attributions, Beliefs, and Risk Appraisals
B Morrongiello and Heather Rennie; 1998


Abstract

Objective:
Assessed for age and sex differences in school-age children's reporting of injury-risk behaviors, ratings of injury-risk in various play situations, attributions for injuries (self, other, bad luck), and beliefs about their vulnerability to injury in comparison to their peers (more, less, comparable vulnerability).

Methods:
We used a structured interview and drawings that depicted children showing wary or confident facial expressions when engaged in injury-risk play activities.

Results:
Children's reported risk taking could be predicted from their risk appraisals, beliefs about the likelihood of injury, and attributions of injuries to bad luck, and these factors resulted in 80% correct assignment of cases by sex in a discriminant analysis. The wary affect display resulted in higher injury-risk ratings than the confident display, with this effect being greater for girls than boys.

Conclusions:
Cognitive-based factors differentiate boys from girls and contribute to sex differences in children's injury-risk behaviors.

Freitag, 18. Oktober 2013

Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments

Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments
Justin Kruger and David Dunning; 1999


Abstract

People tend to hold overly favorable views of their abilities in many social and intellectual domains. The authors suggest that this overestimation occurs, in part, because people who are unskilled in these domains suffer a dual burden: Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it. Across 4 studies, the authors found that participants scoring in the bottom quartile on tests of humor, grammar, and logic grossly overestimated their test performance and ability. Although their test scores put them in the 12th percentile, they estimated themselves to be in the 62nd. Several analyses linked this miscalibration to deficits in metacognitive skill, or the capacity to distinguish accuracy from error. Paradoxically, improving the skills of participants, and thus increasing their metacognitive competence, helped them recognize the limitations of their abilities.


















































































[See also: "Why the Unskilled Are Unaware"
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2702783/]

Literacy and Numeracy Are More Heritable Than Intelligence in Primary School

Literacy and Numeracy Are More Heritable Than Intelligence in Primary School
Yulia Kovas et al.; 2013


Abstract

Because literacy and numeracy are the focus of teaching in schools, whereas general cognitive ability (g, intelligence) is not, it would be reasonable to expect that literacy and numeracy are less heritable than g. Here, we directly compare heritabilities of multiple measures of literacy, numeracy, and g in a United Kingdom sample of 7,500 pairs of twins assessed longitudinally at ages 7, 9, and 12. We show that differences between children are significantly and substantially more heritable for literacy and numeracy than for g at ages 7 and 9, but not 12. We suggest that the reason for this counterintuitive result is that universal education in the early school years reduces environmental disparities so that individual differences that remain are to a greater extent due to genetic differences. In contrast, the heritability of g increases during development as individuals select and create their own environments correlated with their genetic propensities.

[see also: http://drjamesthompson.blogspot.co.uk/2013/08/original-paper-strong-genetic-influence.html & http://drjamesthompson.blogspot.co.uk/2013/10/heritability-estimates-and-analysis-of.html]

Mittwoch, 16. Oktober 2013

Co-ruminating increases stress hormone levels in women

Co-ruminating increases stress hormone levels in women
Jennifer Byrd Craven et al.; March 2008
Hormones and Behavior


Abstract

Same-sex friendships are an important source of social support and typically contribute to positive adjustment. However, there can be adjustment trade-offs if the friends co-ruminate (i.e., talk excessively about problems) in that co-rumination is related to having close friendships but also to increased internalizing symptoms. The current study utilized an experimental manipulation that elicited co-rumination in young women and thus mirrored an everyday response to stress. Observed co-rumination was associated with a significant increase in the stress hormone, cortisol (after controlling for self-reported co-rumination and for cortisol levels assessed before the discussion of problems). These findings suggest that co-rumination can amplify, rather than mitigate, the hormonal stress response to personal life stressors.

[Möglicherweise erklärt das auch, weshalb mancher Mann die  'gesunde Verdrängung' der Ko-Rumination vorzieht.]

Dienstag, 15. Oktober 2013

Risk as a payoff variance:

"Theory and research in behavioral ecology, economics, and psychology have converged on a conception of "risk" as a payoff variance. ... The riskier of two choices with equal expected values is that with the higher payoff variance. Preference for that option is called risk proneness or risk seeking, while preference for the low-variance option is called risk aversion."

M. Daly & M. Wilson

Risk Taking:

>[The] sexes differ in risk taking from childhood. One of the best measures of physical risk taking in children is the incidence of accidental death and injury. In most industrialized countries, including the United States, accidents are the leading cause of death for children older than one year. A World Health Organization study of accidental-death rates in fifty countries found a substantially higher rate for boys in all countries, with a ratio of male to female deaths of 1.9:1 in Europe and 1.7:1 in non-European countries. Notwithstanding greater equality and socially sanctioned androgyny, the male/female accidental-death ratio actually increased in the United States from 1960 to 1979.
Greater risk taking among boys is a robust finding. Boys are exposed to greater risks not only because they are more likely to engage in risky behaviors, but also because when engaging in the same activity as girls, they are more likely to perform it in a risky manner. Boys are substantially more likely to approach hazardous items than girls, and they differ in how they approach them, with girls tending to look and point and boys tending to touch and retrieve them.
Several factors appear to account for the greater inclination of boys to engage in risky activity. Boys tend to have both a higher activity level and poorer impulse control, both traits that are associated with injury rates. Three factors are correlated with self-reported risk taking in both boys and girls: attribution of injuries to bad luck, a belief that one is less vulnerable to injury than one's peers, and downplaying the degree of risk. Boys score higher than girls on all three of these traits.
Boys are less likely than girls to abstain from a risky activity simply because they have seen a peer injured while engaging in the same activity. The best predictor of girls' willingness to take a particular risk is their belief about the likelihood of getting hurt, while for boys it is the perceived severity of the injury. That is, girls tend to avoid risks if they think they might get hurt, while boys seem to be willing to take risks if they do not think they will get too hurt. It is possible, however, that positive attitudes about risk may result in part from risk taking, rather than causing it.
In adolescence and adulthood, sex differences in risk taking increase. Men are disproportionately involved in risky recreational activities such as car racing, sky diving, and hang gliding. Indeed, sex is the variable most predictive of the extent of participation in high-risk recreation. The driving style of men also shows a greater propensity toward risk. Men are disproportionately represented in risky employment, as well. Over 90 percent of all workplace deaths in the United States are males. A list of dangerous occupations is a list of disproportionately male occupations: fisherman, logger, airplane pilot, structural metal worker, coal miner, oil and gas extraction occupations, water transportation occupations, construction laborer, taxicab driver, roofer, and truck driver.
Men's greater propensity to risk their lives is demonstrated by a study of the recipients of awards granted by the Carnegie Hero Fund Commission. Of the 676 acts of heroism recognized from 1989 through 1995, 92 percent were performed by males. Moreover, over one-half of these rescued by women were known to the rescuer, while over two-thirds of those rescued by men were strangers. Although this is not a random sample of heroes, since one must be nominated for the award, it is likely that, if anything, the sex difference is understated because acts of heroism by women would tend to attract more attention than those by men.
Risk taking is statistically correlated with a number of other stereotypically male traits. People who rate high on achievement and dominance, for example, tend to be high risk takers. Risk taking and competitiveness may be related, since competition-prone individuals tend to be willing to take greater risks in pursuit of their competitive objective. High risk takers also fight more frequently, are more socially aggressive, take more dares, and participate in more rough sports and physical activities such as hunting, mountain climbing, and auto racing. In contrast, risk taking is negatively associated with a number of stereotypically female traits: affiliation, nurturance, succorance, deference, and abasement.
Psychologist Elizabeth Arch has suggested that the sex differences in achievement orientation ... may be explained in part by sex differences in risk taking. From an early age, females are more averse not just to physical risk but also to social risk, and they "tend to behave in a manner that ensures continued social inclusion". This aversion to risk may be partially responsible for women's disproportionately low representation in positions involving "career risk", which may be adversely affect their prospects for advancement. This pattern suggests that what is sometimes labeled women's "fear of success" is in fact the more prosaic and easier to understand "fear of failure".
One's willingness to take risks depends in large part upon the relative values that one places on success and failure. A person whose appetite for success exceeds his aversion to failure will be inclined toward action; a person whose aversion to failure exceeds his appetite for success will be inclined not to act. A strong motive to achieve or to avoid failure may also bias the actor's subjective probability of outcome. That is, an achievement-oriented person may have a higher expectation of success than is objectively warranted, while a person with a high motivation to avoid failure may consistently underestimate the chance of success.<

Kingsley R. Browne; 2002;
Biology at Work

Sonntag, 13. Oktober 2013

Men’s mate retention varies with men’s personality and their partner’s personality

Men’s mate retention varies with men’s personality and their partner’s personality
William F. McKibbin et al.; 2013


Abstract

Mate retention is the recurrent adaptive problem of retaining a mate in a relationship. Humans may have evolved mechanisms which motivate behavior in response to this problem. We examined the relation- ship between men’s mate retention and men’s and their partner’s personality in studies of 467 men and 565 women in committed relationships. Participants reported on their own or their partner’s mate retention and both their own and their partner’s personality. Results indicate a negative relationship between men’s Emotional Stability and men’s mate retention and a positive relationship between men’s Agreeableness and men’s benefit-provisioning mate retention. Discussion addresses limitations and directions for future research addressing the links between personality and mate retention.

Samstag, 12. Oktober 2013

Risk-taking as a situationally sensitive male mating strategy

Risk-taking as a situationally sensitive male mating strategy
Michael K Baker and John K Maner; 2008


Abstract

Evolutionary theorists suggest that men engage in risk-taking more than women do in part because, throughout human evolutionary history, men have faced greater sexual selection pressures. We build on this idea by testing the hypothesis that risk-taking reflects a male mating strategy that is sensitive to characteristics of a potential mate. Consistent with this hypothesis, the current experiment demonstrated a positive relationship between mating motivation and risk-taking, but only in men who had been exposed to images of highly attractive females. Moreover, risk-taking in men was associated with enhanced memory for attractive female faces, indicating enhanced processing of their attractive facial characteristics. No relationship between mating motivation and risk-taking was observed in men exposed to images of unattractive women, nor was any such relationship observed in women. This experiment provides evidence that psychological states associated with mating may promote risk-taking, and that these effects are sex specific and are sensitive to situational context.

Freitag, 11. Oktober 2013

Individual differences in risk-propensity:

Individual differences in risk-propensity: Associations between personality and behavioral measures of risk
Sandeep Mishra and Martin L Lalumiere


Abstract

Previous research has demonstrated that various forms of risky behavior are highly associated among individuals, and such personality traits as impulsivity, sensation-seeking, and low self-control are correlated with risk-taking. However, little evidence indicates that self-report measures of personality traits associated with risky behavior significantly correlate with a behavioral preference for risk. We examined whether personality questionnaire measures of traits associated with risk (impulsivity, sensation-seeking, low self-control) were correlated with various behavioral measures of risk (future discounting, probabilistic risky choice). We show that measures of risk-propensity comprise three principal components: Future Discounting, Risky Personality, and Variance Preference. Risky Personality and Variance Preference were significantly correlated. Future Discounting was not associated with either of the other risk components. Together, the results provide some evidence suggesting that stable personality traits may represent proximate mechanisms through which a behavioral preference for risky outcomes manifests.

Donnerstag, 10. Oktober 2013

A Social Neuroscience Perspective on Adolescent Risk-Taking

A Social Neuroscience Perspective on Adolescent Risk-Taking
Laurence Steinberg; 2008


Abstract

This article proposes a framework for theory and research on risk-taking that is informed by developmental neuroscience. Two fundamental questions motivate this review. First, why does risk-taking increase between childhood and adolescence? Second, why does risk-taking decline between adolescence and adulthood? Risk-taking increases between childhood and adolescence as a result of changes around the time of puberty in the brain’s socio-emotional system leading to increased reward-seeking, especially in the presence of peers, fueled mainly by a dramatic remodeling of the brain’s dopaminergic system. Risk-taking declines between adolescence and adulthood because of changes in the brain’s cognitive control system – changes which improve individuals’ capacity for self-regulation. These changes occur across adolescence and young adulthood and are seen in structural and functional changes within the prefrontal cortex and its connections to other brain regions. The differing timetables of these changes make mid-adolescence a time of heightened vulnerability to risky and reckless behavior.

Life history variables and risk-taking propensity

Life history variables and risk-taking propensity
XT Wang, DJ Kruger, A Wilke


Abstract

We examined the effects of life-history variables on risk-taking propensity, measured by subjective likelihoods of engaging in risky behaviors in five evolutionarily valid domains of risk, including between-group competition, within-group competition, environmental challenge, mating and resource allocation, and fertility and reproduction. The effects of life-history variables on risk-taking propensity were domain specific, except for the expected sex difference, where men predicted greater risk-taking than women in all domains. Males also perceived less inherent risk in actions than females across the five domains. Although the age range in the sample was limited, older respondents showed lower risk propensity in both between- and within-group competition. Parenthood reduced risk-taking propensity in within- and between-group competitions. Higher reproductive goal setting (desiring more offspring) was associated with lower risk-taking propensity. This effect was strongest in the risk domains of mating and reproduction. Having more siblings reduced risk-taking propensity (contrary to our initial prediction) in the domains of environmental challenge, reproduction, and between-group competition. Later-born children showed a higher propensity to engage in environmental and mating risks. Last, shorter subjective life expectancy was associated with increased willingness to take mating and reproductive risks. These results suggest that life-history variables regulate human risk-taking propensity in specific risk domains.

Brother–sister differences in the g factor in intelligence:

Brother–sister differences in the g factor in intelligence: Analysis of full, opposite-sex siblings from the NLSY1979
Ian J Deary, Paul Irwing, Geoff Der, Timothy C Bates

There is scientific and popular dispute about whether there are sex differences in cognitive abilities and whether they are relevant to the proportions of men and women who attain high-level achievements, such as Nobel Prizes. A recent meta-analysis (Lynn, R., and Irwing, P. (2004). Sex differences on the progressive matrices: a meta-analysis. Intelligence, 32, 481–498.), which suggested that males have higher mean scores on the general factor in intelligence (g), proved especially contentious. Here we use a novel design, comparing 1292 pairs of opposite-sex siblings who participated in the US National Longitudinal Survey of Youth 1979 (NLSY1979). The mental test applied was the Armed Services Vocational Aptitude Battery (ASVAB), from which the briefer Armed Forces Qualification Test (AFQT) scores can also be derived. Males have only a marginal advantage in mean levels of g (less than 7% of a standard deviation) from the ASVAB and AFQT, but substantially greater variance. Among the top 2% AFQT scores, there were almost twice as many males as females. These differences could provide a partial basis for sex differences in intellectual eminence.

Montag, 7. Oktober 2013

Identifying and explaining apparent universal sex differences in cognition and behavior

Identifying and explaining apparent universal sex differences in cognition and behavior
Lee Ellis; October 2011
Personality and Individual Differences


Abstract

With growing recognition that there are universal sex differences in cognition and behavior, four theories have been proposed to account for these differences: the founder effect theory, the social structuralist theory, the evolutionary theory, and the evolutionary neuroandrogenic (ENAtheory. The latter of these theories is described in considerable detail as offering an explanation for most of 65 recently identifiedapparent universal sex differences (AUSDs) in cognition and behavior. Regarding “ultimate causes” (why), ENA theory asserts that (a) evolutionary-genetic factors incline females to bias their mate choices toward males who are loyal and competent provisioners of resources and (b) males are merely a genetic variant on the female sex selected for responding to female mating biases. In terms of “proximate causes” (how), the theory maintains that high exposure to androgens has evolved to alter the male brain functioning in two specific ways relative to most female brains: (a) suboptimal arousal and (b) a rightward shift in neocortical functioning. These two functional patterns are described and hypothesized to incline males and females to learn differently in many respects. The most fundamental differences involve males learning ways of either complying with or circumventing female mate preferences. Numerous universal sex differences in cognition and behavior are hypothesized to result from these evolved neurohormonal factors, including most of the 65 AUSDs herein summarized in seven categorical tables.















































[full size: click at the image - please inform me if something doesn't work.]

Chimps of a feather sit together: chimpanzee friendships are based on homophily in personality

Chimps of a feather sit together: chimpanzee friendships are based on homophily in personality
Jorg J M Massen and Sonja E Koski
Available online 2 October 2013
Evolution and Human Behavior


Abstract

Several recent studies show that animal friendships, like human friendships, are durable and have fitness benefits by increasing survival, infant survival, or reproductive success. However, the determinants of especially non-kin friendships are unclear. Human non-kin friendships are partly determined by similarity in personality. We investigated personality similarity of friends in 38 captive chimpanzees. Within-subject comparisons revealed that friends are more similar than non-friends in their Sociability and Boldness. Subsequent analyses, including both kin- and non-kin dyads, revealed higher similarity in Sociability among all individuals who sat in contact more often, while in Boldness and Grooming Equity the positive effect of similarity was only found in non-kin individuals’ contact-sitting. Our results show that similar to humans, chimpanzees’ friendships are related to homophily in certain personality characteristics, particularly those relevant for socio-positive and cooperative behaviour. We suggest that having friends similar to self in personality decreases uncertainty in interactions by promoting reliability especially in cooperative contexts, and is consequently adaptive. Further, we suggest that homophily in human friendships dates back at least to our last common ancestor with chimpanzees.