Same Genes, Different Brains: Neuroanatomical Differences Between Monozygotic Twins Discordant for Musical Training

Same Genes, Different Brains: Neuroanatomical Differences Between Monozygotic Twins Discordant for Musical Training. Örjan de Manzano Fredrik Ullén. Cerebral Cortex, https://doi.org/10.1093/cercor/bhx299

Abstract: Numerous cross-sectional and observational longitudinal studies show associations between expertise and regional brain anatomy. However, since these designs confound training with genetic predisposition, the causal role of training remains unclear. Here, we use a discordant monozygotic (identical) twin design to study expertise-dependent effects on neuroanatomy using musical training as model behavior, while essentially controlling for genetic factors and shared environment of upbringing. From a larger cohort of monozygotic twins, we were able to recruit 18 individuals (9 pairs) that were highly discordant for piano practice. We used structural and diffusion magnetic resonance imaging to analyze the auditory-motor network and within-pair differences in cortical thickness, cerebellar regional volumes and white-matter microstructure/fractional anisotropy. The analyses revealed that the musically active twins had greater cortical thickness in the auditory-motor network of the left hemisphere and more developed white matter microstructure in relevant tracts in both hemispheres and the corpus callosum. Furthermore, the volume of gray matter in the left cerebellar region of interest comprising lobules I–IV + V, was greater in the playing group. These findings provide the first clear support for that a significant portion of the differences in brain anatomy between experts and nonexperts depend on causal effects of training.

Keywords: expertise, MRI, music, neuroanatomy, twins

Zero Likes – Symbolic interactions and need satisfaction online

Zero Likes – Symbolic interactions and need satisfaction online. Sabine Reich, Frank M.Schneider, and Leonie Heling. Computers in Human Behavior, Volume 80, March 2018, Pages 97-102. https://doi.org/10.1016/j.chb.2017.10.043

Highlights
•    Likes are a form of symbolic interaction within social networking sites (SNS).
•    Zero Likes on SNS threaten fundamental needs and affect.
•    Likes from close friends (vs. acquaintances) best satisfy fundamental needs.

Abstract: The paper looks at the symbolic interactions on social networking sites, such as Likes on Facebook, and their role in users' sense of social in- or exclusion. In an online experiment, users of Facebook were asked to write a possible status update and then received note about the numbers of hypothetical Likes they received (zero, two, or thirty) and who (close friends or acquaintances) pressed the Like button. Multivariate analysis of variances showed that belongingness and self-esteem needs are threatened when people do not receive Likes. In contrast, more Likes seem to satisfy these needs better. The influence of who gives the Likes is minor compared to the sheer number of Likes.

Paying Down Credit Card Debt for Hotels Not Sofas

Quispe-Torreblanca, Edika and Stewart, Neil and Gathergood, John and Loewenstein, George, The Red, the Black, and the Plastic: Paying Down Credit Card Debt for Hotels Not Sofas (September 15, 2017). Available at SSRN: https://ssrn.com/abstract=3037416

Abstract: Using transaction data from a sample of 1.8 million credit card accounts, we provide the first field test of a major prediction of Prelec and Loewenstein’s (1998) theory of mental accounting. The prediction is that consumers will pay off expenditure on transient forms of consumption more quickly than expenditure on durables. According to the theory, this is because the pain of paying can be offset by the future anticipated pleasure of consumption only when money is spent on consumption that endures over time. Consistent with the prediction, we found that repayment of debt incurred for non-durable goods is an absolute 9% more likely than repayment of debt incurred for durable goods. The size of this effect is comparable to an increment in 15 percentage points in the credit card APR.

Keywords: mental accounting, credit cards, debt repayment
JEL Classification: D14, D91

Common sense in the New York Times: Many of our most demonized foods are actually fine for us. Like salt.

You Don’t Need to ‘Eat Clean’. By Aaron E. Carroll. The New York Times, November 5, 2017, Page SR10, https://www.nytimes.com/2017/11/04/opinion/sunday/relax-you-dont-need-to-eat-clean.html

We talk about food in the negative: What we shouldn’t eat, what we’ll regret later, what’s evil, dangerously tempting, unhealthy.

The effects are more insidious than any overindulgent amount of “bad food” can ever be. By fretting about food, we turn occasions for comfort and joy into sources of fear and anxiety. And when we avoid certain foods, we usually compensate by consuming too much of others.

All of this happens under the guise of science. But a closer look at the research behind our food fears shows that many of our most demonized foods are actually fine for us. Taken to extremes, of course, dietary choices can be harmful — but that logic cuts both ways.

Consider salt. It’s true that, if people with high blood pressure consume a lot of salt, it can lead to cardiovascular events like heart attacks. It’s also true that salt is overused in processed foods. But the average American consumes just over three grams of sodium per day, which is actually in the sweet spot for health.

Eating too little salt may be just as dangerous as eating too much. This is especially true for the majority of people who don’t have high blood pressure. Regardless, experts continue to push for lower recommendations.

Many of the doctors and nutritionists who recommend avoiding certain foods fail to properly explain the magnitude of their risks. In some studies, processed red meat in large amounts is associated with an increased relative risk of developing cancer. The absolute risk, however, is often quite small. If I ate an extra serving of bacon a day, every day, my lifetime risk of colon cancer would go up less than one-half of 1 percent. Even then, it’s debatable.

Nevertheless, we’ve become more and more susceptible to arguments that we must avoid certain foods completely. When one panic-du-jour wanes, we find another focus for our fears. We demonized fats. Then cholesterol. Then meat.

For some people in recent years, gluten has become the enemy, even though wheat accounts for about 20 percent of the calories consumed worldwide, more than pretty much any other food. Fewer than 1 percent of people in the United States have a wheat allergy, and fewer than 1 percent have celiac disease, an autoimmune disorder that requires sufferers to abstain from gluten. Gluten sensitivity (the catchall disorder that leads many Americans to abstain from gluten) is not well defined, and most people who self-diagnose don’t meet the criteria.

Nonetheless, at least one in five Americans regularly chooses gluten-free foods, according to a 2015 poll. Sales of products with gluten-free labels rose to $23 billion worldwide in 2014, up from $11.5 billion worldwide in 2010.

Gluten-free diets can lead to deficiencies in nutrients such as vitamin B, folate and iron. Compared with regular bagels, gluten-free ones can have a quarter more calories, two and a half times the fat, half the fiber and twice the sugar. They also cost more.

The hullabaloo over gluten echoes the panic over MSG that began roughly half a century ago, and which has yet to fully subside. MSG, or monosodium glutamate, is nothing more than a single sodium atom added to glutamic acid — an amino acid that is a key part of the mechanism by which our cells create energy. Without it, all oxygen-dependent life as we know it would die.

A 1968 letter in The New England Journal of Medicine started the frenzy; the writer reported feeling numbness, weakness and palpitations after eating at a Chinese restaurant. A few limited studies followed, along with a spate of news articles. Before long, nutrition experts and consumer advocates such as Ralph Nader were calling for MSG to be banned. The Food and Drug Administration never had to step in; food companies saw the writing on the wall, and dropped MSG voluntarily.

Many people still wrongly believe that MSG is poison. We certainly don’t need MSG in our diet, but we also don’t need to waste effort avoiding it. Our aversion to it shows how susceptible we are to misinterpreting scientific research and how slow we are to update our thinking when better research becomes available. There’s no evidence that people suffer disproportionately from the afflictions — now ranging from headaches to asthma — that MSG-averse cultures commonly associate with this ingredient. In studies all over the world, the case against MSG just doesn’t hold up.

Too often, we fail to think critically about scientific evidence. Genetically modified organisms are perhaps the best example of this.

G.M.O.s are, in theory, one of our best bets for feeding the planet’s growing population. When a 2015 Pew poll asked Americans whether they thought it was generally safe or unsafe to eat modified foods, almost 60 percent said it was unsafe. The same poll asked scientists from the American Association for the Advancement of Science the same question. Only 11 percent of them thought G.M.O.s were unsafe.

Most Americans, at least according to this poll, don’t seem to care what scientists think. In fact, Americans disagree with scientists on this issue more than just about any other, including a host of contentious topics such as vaccines, evolution and even global warming.

If people want to avoid foods, even if there’s no reason to, is that really a problem?

The answer is: yes. Because it makes food scary. And being afraid of food with no real reason is unscientific — part of the dangerous trend of anti-intellectualism that we confront in many places today.

Food should be a cause for pleasure, not panic. For most people, it’s entirely possible to eat more healthfully without living in terror or struggling to avoid certain foods altogether. If there’s one thing you should cut from your diet, it’s fear.

Aaron E. Carroll (@aaronecarroll) is a professor of pediatrics at Indiana University School of Medicine, and a regular contributor to The Upshot. He is the author of “The Bad Food Bible: How and Why to Eat Sinfully,” from which this essay was adapted.

The differential impact of knowledge depth and knowledge breadth on creativity over individual careers

The differential impact of knowledge depth and knowledge breadth on creativity over individual careers. Pier Vittorio Mannucci and Kevyn Yong. Academy of Management Journal, http://amj.aom.org/content/early/2017/10/23/amj.2016.0529

Abstract: While usually argued to be fostering creativity, the effect of knowledge depth and breadth on creativity is actually mixed. We take a dynamic approach to the knowledge-creativity relationship and argue that the effect of knowledge depth and knowledge breadth is likely to be contingent on career age. We propose that individuals' knowledge structures become increasingly rigid as career age grows and that because of this, knowledge depth and breadth have different effects on creativity at different points of the career. More specifically, we hypothesize that knowledge depth is more beneficial for creativity in earlier stages of one's career, when creators need to increase the complexity of knowledge structures, while knowledge breadth is more beneficial in later stages, when flexibility is most needed. We test and find support for our hypotheses in a longitudinal study set in the context of the Hollywood animation industry, a setting characterized by the presence of a variety of creators involved in knowledge-intensive activities. Theoretical and practical implications of the results are discussed.

An Evolutionary Perspective on Orgasm

Gallup, G. G., Jr., Towne, J. P., & Stolz, J. A. (2017). An Evolutionary Perspective on Orgasm. Evolutionary Behavioral Sciences, http://dx.doi.org/10.1037/ebs0000104

Abstract: The capacity to experience an orgasm evolved to promote high-frequency sex in species with low reproductive rates. Growing evidence shows that orgasms also have a variety of other reproductive consequences. Based on a distinction between orgasm frequency and orgasm intensity, there is emerging evidence in humans that orgasms function to promote and fine tune what are often very different, sex-specific reproductive outcomes. We provide an overview of the effect of hormonal contraceptives on orgasm, mate choice, and sexual satisfaction. The effects of sex during pregnancy, along with orgasm induced vocalizations, facial expressions during orgasm, and the putative effects of semen exposure on orgasm and sexual functioning in females are also discussed. Recent research suggests that female orgasms evolved to promote good mate choices, and we propose that instances of orgasmic dysfunction in many women may be a byproduct of an inability to find and/or retain high-quality male partners.

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Factor into this matrix evidence showing that women who engage in extrapair copulations are more likely to be in the fertile phase of their cycle, less likely to use contraception, and more likely to experience orgasm (Baker & Bellis, 1993), and it becomes apparent that females may have been shaped by their evolutionary history to use extrapair copulations to bare children sired by genetically superior males and/or to increase the range of genetic variation among their existing children (Gallup & Burch, 2006).  By the time a woman has had three children sired by the same man, she will have sampled roughly 87.5% of his genes, and therefore, any additional children sired by the same man will be increasingly redundant genetic samples (Gallup & Ampel, 2017). By targeting high-quality males for extrapair copulations women, can have children sired by genetically superior males and as an added bonus, children sired by different males represents a hedge against an uncertain future. Consistent with this analysis women are not only more likely to experience orgasm, they also report more intense orgasms as a result of extrapair copulations (Gallup, Burch, & Mitchell, 2006). Therefore, if you are a woman whether you experience an orgasm and who you experience an orgasm with may make an important difference. Moreover, it seems reasonable to suppose that variation in orgasm intensity ought to be proportional to the magnitude of the vaginal and intrauterine contractions that occur during orgasm, which puts a reproductive premium on orgasm intensity. Suffice it to say that for all of these reasons, Lloyd’s (2005) claimed that orgasm in women was not subject to natural selection is untenable.

In contrast to females, it has been suggested that variation in ratings of orgasm intensity among males is an index or proxy for sperm recruitment (Gallup et al., 2012). Gallup et al.  predicted that the ejaculate which accompanies more intense orgasms will contain more sperm and higher concentrations of other seminal chemicals tailored to make conception more likely. For example, recent research by Pham et al. (2016) shows that estimates of ejaculate volume as a measure of ejaculate quality, correlate with the duration of cunnilingus as a prelude to sexual intercourse. Because of a history of competition for paternity, coupled with the high costs of being cuckolded, we predict that indications of partner infidelity ought to also be conducive to the occurrence of more intense orgasms in men. In other words, while more intense female orgasms may function as a mate choice mechanism, more intense orgasms in men may be a reflection of sperm recruitment mechanisms that function to compete with the possibility of rival male semen in their partner’s reproductive tract. A seemingly counterintuitive but nonetheless testable prediction that follows from this analysis would be that males who fantasize about partner infidelity during sex or masturbation would be expected to experience more intense orgasms. The growing prevalence of websites on the Internet that cater to such male fantasies provides suggestive evidence for such an effect. Research by Joyal, Cossette, and Lapierre (2015), showing that a significant proportion of men fantasize about having sex with couples that they and their partner know as well as couples they do not, is also consistent with this hypothesis.

A corollary prediction would be that variation in the reproductive value of different female partners ought to be proportional to corresponding variation in male orgasm intensity.  This could be tested by partitioning variation in the appearance of females depicted in pornographic videos to see if the composition of semen samples taken from males who masturbate while watching such videos varies as a function of how they rate their orgasms and as a function of objective variation in different fitness indicators among female pornography stars such as waist to hip ratios, facial attractiveness, breast size, and so forth. Variations in most physical dimensions of interpersonal attraction and sex appeal are well-documented proxies for underlying differences in health and fertility (Gallup & Frederick, 2010).

Recently, Joseph, Sharma, Agarwal, and Sirot (2015) found that ejaculate quality (as indexed by parameters such as ejaculate volume and number of motile sperm) goes up when men are exposed to novel/unfamiliar women, and men ejaculate faster when shown a new woman following a series of repeated exposures to the same woman. Thus, not surprisingly, the Coolidge effect (for a review, see Dewsbury, 1981) appears to be accompanied by testicular adjustments that make for a higher quality ejaculate, and we predict that under such conditions, males will report corresponding increases in orgasm intensity as well.

It is interesting that there may even be an assortative mating/social comparison component to such testicular adjustments. Leivers, Rhodes, and Simmons (2014a) found an interaction between male mate value and female attractiveness for measures of ejaculate quality.  Men with high mate value (based on attractiveness, dominance and self-perceived mate value) only produced high-quality ejaculates when given the opportunity to view images of attractive females. Just the opposite was true for men of low mate value, who produced lower quality ejaculates when viewing attractive females.  Thus, there appears to be a context dependent effect on ejaculate quality that interacts with the mate value of the male and the attractiveness of the female. High-value males only allocate high-quality ejaculates to attractive females.  Also implicating the existence of specialized ejaculate allocation mechanisms based on tradeoff effects, Leivers, Rhodes, and Simmons (2014b) found that men who engage in fewer mate guarding behaviors produce higher quality ejaculates.

In the context of the social psychological properties of orgasm and intersexual reproductive competition, evidence shows that some women fake orgasms in an effort to promote partner retention (Kaighobadi, Shackelford, & Weekes-Shackelford, 2012). Consistent with these results implicating attempts by women to feign orgasms to manipulate their mates, Brewer and Hendrie (2011) found that rather than being triggered by orgasm, copulatory vocalizations by some women were more likely to occur during male ejaculation. Indeed, Ellsworth and Bailey (2013) found that faked orgasms were correlated with the likelihood that women had engaged in sexual infidelity. Ellsworth and Bailey also found that males were more sexually satisfied with females who experienced more intense and frequent orgasms, and therefore, they speculate that variation in female orgasms may convey information about the probability of paternity.

Do Orgasms Give Women Feedback About Mate Choice? Gordon G. Gallup et al. Evolutionary Psychology, 2014. 12(5): 957-977. https://www.researchgate.net/publication/308086891

Abstract: The current study represents a preliminary investigation of the extent to which
female orgasm functions to promote good mate choices. Based on a survey of heterosexual female college students in committed relationships, how often women experienced orgasm as a result of sexual intercourse was related to their partner’s family income, his selfconfidence, and how attractive he was. Orgasm intensity was also related to how attracted they were to their partners, how many times they had sex per week, and ratings of sexual satisfaction. Those with partners who their friends rated as more attractive also tended to have more intense orgasms. Orgasm frequency was highly correlated (r = .82) with orgasm intensity, and orgasm intensity was a marginally better predictor of sexual satisfaction than orgasm frequency. Sexual satisfaction was related to how physically attracted women were to their partner and the breadth of his shoulders. Women who began having sexual intercourse at earlier ages had more sex partners, experienced more orgasms, and were more sexually satisfied with their partners. We also identified an ensemble of partner psychological traits (motivation, intelligence, focus, and determination) that predicted how often women initiated sexual intercourse. Their partner’s sense of humor not only predicted his self-confidence and family income, but it also predicted women’s propensity to initiate sex, how often they had sex, and it enhanced their orgasm frequency in comparison with other partners.

Keywords: orgasm frequency, orgasm intensity, sexual satisfaction, female initiated
intercourse, precocial sexual experience, partner sense of humor

Bystanders intervene to impede grooming in Western chimpanzees and sooty mangabeys

Bystanders intervene to impede grooming in Western chimpanzees and sooty mangabeys. Alexander Mielke, Liran Samuni, Anna Preis, Jan F. Gogarten, Catherine Crockford, Roman M. Wittig. Royal Society Open Science, DOI: 10.1098/rsos.171296

Abstract: Grooming interactions benefit groomers, but may have negative consequences for bystanders. Grooming limits bystanders' grooming access and ensuing alliances could threaten the bystander's hierarchy rank or their previous investment in the groomers. To gain a competitive advantage, bystanders could intervene into a grooming bout to increase their own grooming access or to prevent the negative impact of others' grooming. We tested the impact of dominance rank and social relationships on grooming intervention likelihood and outcome in two sympatric primate species, Western chimpanzees (Pan troglodytes verus) and sooty mangabeys (Cercocebus atys atys). In both species, rather than increasing their own access to preferred partners, bystanders intervened mainly when an alliance between groomers could have a negative impact on them: when the lower-ranking groomer was close to the bystander in rank, when either groomer was an affiliation partner whose services they could lose, or the groomers were not yet strongly affiliated with each other. Thus, bystanders in both species appear to monitor grooming interactions and intervene based on their own dominance rank and social relationships, as well as triadic awareness of the relationship between groomers. While the motivation to intervene did not differ between species, mangabeys appeared to be more constrained by dominance rank than chimpanzees.

The Humanizing Voice: Speech Reveals, and Text Conceals, a More Thoughtful Mind in the Midst of Disagreement

The Humanizing Voice: Speech Reveals, and Text Conceals, a More Thoughtful Mind in the Midst of Disagreement. Juliana Schroeder, Michael Kardas, Nicholas Epley. Psychological Science,  https://doi.org/10.1177/0956797617713798

Abstract: A person’s speech communicates his or her thoughts and feelings. We predicted that beyond conveying the contents of a person’s mind, a person’s speech also conveys mental capacity, such that hearing a person explain his or her beliefs makes the person seem more mentally capable—and therefore seem to possess more uniquely human mental traits—than reading the same content. We expected this effect to emerge when people are perceived as relatively mindless, such as when they disagree with the evaluator’s own beliefs. Three experiments involving polarizing attitudinal issues and political opinions supported these hypotheses. A fourth experiment identified paralinguistic cues in the human voice that convey basic mental capacities. These results suggest that the medium through which people communicate may systematically influence the impressions they form of each other. The tendency to denigrate the minds of the opposition may be tempered by giving them, quite literally, a voice.

Check also Your attention makes me smile: Direct gaze elicits affiliative facial expressions. Jari K. Hietanen et al. Biological Psychology, http://www.bipartisanalliance.com/2017/11/your-attention-makes-me-smile-direct.html

Speaking From Ignorance: Not Agreeing With Others We Believe Are Correct

Speaking From Ignorance: Not Agreeing With Others We Believe Are Correct. Bert Hodges et al. Journal of Personality and Social Psychology, 2014, Vol. 106, No. 2, 218–234. DOI: 10.1037/a0034662

Abstract: Values-pragmatics theory (Hodges & Geyer, 2006) predicts that people will sometimes disagree with others they believe are correct, for reasons similar to those explaining agreement with incorrect answers in an Asch (1956) situation. In 3 experiments, we found evidence that people in a position of ignorance sometimes do not agree with the correct answers of others in positions of knowledge. Experiments 1a and 1b found this speaking-from-ignorance (SFI) effect occurred 27% of the time. Experiment 2 introduced experimental controls and self-report data indicating that the SFI effect (30%) was generated by realizing values (e.g., truth, social solidarity) and pragmatic constraints to act cooperatively, rather than by a wide array of alternatives (e.g., normative pressure, reactance). Experiment 3 experimentally manipulated concern for truthfulness, yielding 49% nonagreeing answers, even though there were monetary incentives to give correct, agreeing answers. The overall pattern suggests that people are not so much conformists or independents as they are cooperative truth tellers under social and moral constraints. Results, while surprising for social influence theories, illustrate the dynamics of divergence and convergence that appear across studies in cultural anthropology and developmental psychology, as well as in social psychology.

Keywords: conformity, divergence, pragmatics, truth, values

Users who feature either cat or dog images in their tweets are more neurotic, less conscientious, and less agreeable

Personality Profiles of Users Sharing Animal-related Content on Social Media. Courtney Hagan, Jordan Carpenter, Lyle Ungar & Daniel Preotiuc-Pietro. Anthrozoös, Volume 30, 2017, Issue 4, Pages 671-680. http://www.tandfonline.com/doi/abs/10.1080/08927936.2017.1370235

ABSTRACT: Animal preferences are thought to be linked with more salient psychological traits of people, and most research examining owner personality as a differentiating factor has obtained mixed results. The rise in usage of social networks offers users a new medium in which they can broadcast their preferences and activities, including about animals. In two studies, the first on Facebook status updates and the second on images shared on Twitter, we revisited the link between Big Five personality traits and animal preference, specifically focusing on cats and dogs. We used automatic content analysis of text and images to unobtrusively measure preference for animals online using large datasets. In study 1, a dataset of Facebook status updates (n = 72,559) were analyzed and it was found that those who mentioned ownership of a cat (by using the phrase “my cat” (n = 5,053)) in their status updates were more open to experience, introverted, neurotic, and less conscientious when compared with the general population. Users mentioning ownership of a dog (by using “my dog” (n = 8,045)) were only less conscientious compared with the rest of the population. In study 2, a dataset of Twitter images was analyzed and revealed that users who featured either cat (n = 1,036) or dog (n = 1,499) images in their tweets were more neurotic, less conscientious, and less agreeable than those who did not. In addition, posting images containing cats was specific to users higher in openness, while posting images featuring dogs was associated with users higher in extraversion. These findings taken together align with some previous findings on the relationship between owner personality and animal preference, additionally highlighting some social media-specific behaviors.

Keywords: Big Five, cat people, dog people, Facebook, social media, Twitter

Supernatural Belief Is Not Modulated by Intuitive Thinking Style or Cognitive Inhibition

Supernatural Belief Is Not Modulated by Intuitive Thinking Style or Cognitive Inhibition. Miguel Farias et al. Scientific Reports 7, Article number: 15100 (2017), doi:10.1038/s41598-017-14090-9

Abstract: According to the Intuitive Belief Hypothesis, supernatural belief relies heavily on intuitive thinking—and decreases when analytic thinking is engaged. After pointing out various limitations in prior attempts to support this Intuitive Belief Hypothesis, we test it across three new studies using a variety of paradigms, ranging from a pilgrimage field study to a neurostimulation experiment. In all three studies, we found no relationship between intuitive or analytical thinking and supernatural belief. We conclude that it is premature to explain belief in gods as ‘intuitive’, and that other factors, such as socio-cultural upbringing, are likely to play a greater role in the emergence and maintenance of supernatural belief than cognitive style.

In humans, some sexual traits suggest monogamous mating, while others suggest selection for polygyny

Humans as a model species for sexual selection research. Michael Lawrence Wilson, Carrie M. Miller, Kristin N. Crouse. Proceedings of the Royal Society B, Volume 284, issue 1866. DOI: 10.1098/rspb.2017.1320

Abstract: Ever since Darwin, questions about humans have driven sexual selection research. While studies of other organisms are often justified as useful for improving understanding of humans, humans themselves can be useful models. Although humans present some drawbacks as model organisms (complicated societies, slow reproduction and strong ethical constraints on experimental options), humans nonetheless offer many advantages (being abundant, accessible and having detailed historical records for some populations). As an additional challenge, humans exhibit a rather puzzling combination of traits. Some traits (pair-bonding, biparental care and modest sexual dimorphism in body size) suggest selection for monogamous mating, while other traits (including sexual dimorphism in body composition and appearance) suggest selection for polygyny. Such puzzles have motivated research on other species, resulting in a rich set of comparative data that provides insights into humans and other species. Recent studies of visual trait dimorphism suggest that human appearance reflects adaptation for multi-level societies, rather than high levels of polygyny. In addition to biological traits, human cultural traits have undergone rapid evolution. Changes in subsistence strategies profoundly affect opportunities for sexual selection. The enormous variability of human behaviour and ecology provides abundant opportunities to test key hypotheses, and poses challenging puzzles for future research.



Check also Competing for Love: Applying Sexual Economics Theory to Mating Contests. Roy F. Baumeister et al. Journal of Economic Psychology, July 29 2017, http://www.bipartisanalliance.com/2017/08/competing-for-love-applying-sexual.html

Personality traits AND social relationships are deeply entwined in a bidirectional way

Mund, M., Jeronimus, B. F., & Neyer, F. J. (in press). Personality and social relationships: As thick as thieves. In C. Johansen (Ed.), Your personality makes you ill: Scientific proof or wishful thinking?  San Diego: Elsevier, expected Jan 2018. Available from: https://www.researchgate.net/publication/319527661_Personality_and_social_relationships_As_thick_as_thieves

Abstract: This chapter shows that personality traits and social relationships are deeply entwined in a bidirectional way: Individuals select relationships partly based on their personality traits but at the same time develop across the lifespan partly in response to changes in their social environment. Life transitions are an important catalyst of changes in personality-relationship transactions. We argue that personality traits and social relationships are so closely tied that, in our view, the link between personality and health can only be understood against the backdrop of individuals’ relationships.

Deviations from expectations drive tipping behavior more so than wins and losses, and especially close wins

Sports Sentiment and Tipping Behavior. Qi Ge. Journal of Economic Behavior & Organization, https://doi.org/10.1016/j.jebo.2017.10.016

Highlights
•    Utilize data on taxi rides in New York City to investigate how emotions due to sporting event outcomes affect passengers’ tipping behavior.
•    Formulate and test a reference-dependent preferences framework of tipping behavior.
•    Find that deviations from expectations drive tipping behavior more so than wins and losses, with the most salient effects found under unexpected close wins.
•    Find no support for loss aversion in the context of tipping behavior.

Abstract: This paper utilizes a high frequency dataset on taxi rides in New York City to investigate how emotions due to sporting event outcomes affect passengers’ tipping behavior. I formulate and empirically test a reference-dependent preferences framework of tipping behavior. The results indicate that the tipping amounts are driven by deviations from expectations much more so than wins and losses, with the most salient effects found under unexpected close wins. However, there is no support for loss aversion. The findings suggest that loss averse behavior may be subdued in the presence of social norms while surprises can result in freedom on the upside of tipping.

JEL classification: D03; D12; L83; Z2
Keywords: Reference-dependent preferences; Tipping behavior; Social norms

Your attention makes me smile: Direct gaze elicits affiliative facial expressions

Your attention makes me smile: Direct gaze elicits affiliative facial expressions. Jari K. Hietanen et al. Biological Psychology, https://doi.org/10.1016/j.biopsycho.2017.11.001

Highlights
•    Facial EMG and autonomic responses were measured to another individual’s direct and averted gaze.
•    Greater zygomatic responses were elicited by seeing another person with direct than averted gaze.
•    The results suggest that another individual’s direct gaze is an affiliative, positive signal.

Abstract: Facial electromyographic responses and skin conductance responses were measured to investigate whether, in a neutral laboratory environment, another individual’s direct gaze elicits a positive or negative affective reaction in the observer. The results showed that greater zygomatic responses associated with positive affect were elicited by seeing another person with direct as compared to averted gaze. The zygomatic responses were greater in response to another person’s direct gaze both when the participant’s own gaze was directed towards the other and when the participant was not looking directly towards the other. Compatible with the zygomatic responses, the corrugator activity (associated with negative affect) was decreased below baseline more in response to another person’s direct than averted gaze. Replicating previous research, the skin conductance responses were greater to another person’s direct than averted gaze. The results provide evidence that, in a neutral context, another individual’s direct gaze is an affiliative, positive signal.

Keywords: affect; facial EMG; eye contact; facial expression; SCR