Towards an Archaeology of Pain? Assessing the Evidence from Later Prehistoric Bog Bodies

Towards an Archaeology of Pain? Assessing the Evidence from Later Prehistoric Bog Bodies. Henry P. Chapman, Benjamin R. Gearey. Oxford Journal of Archaeology, https://doi.org/10.1111/ojoa.12165

Summary: This paper highlights the potential for what could be termed an ‘archaeology of pain’, reflecting on the potential significance and role of the infliction, suffering, endurance and observation of pain by individuals in the past. It presents a case study of ‘bog bodies’, human remains recovered from wetland which, due to the anoxic, waterlogged conditions, preserves human flesh and associated evidence, including injuries and cause of death. The central argument is that evidence from pathological investigations of certain later prehistoric bodies provides hitherto neglected information concerning the embodied experience of pain, in particular its duration and intensity, which may be central to the interpretation of these events. This understanding can be framed not only in terms of the experience of pain by the victims, but also in the potential perception of pain and suffering by those inflicting these and potentially by any observers of the final moments of these individuals.

Is NATO Deterrence a Paper Tiger? NATO is too slow of thought, decision, & foot to fight a contemporary war; on the eve of a short war, the US would put together a high-end coalition to do the fighting

Judy Asks: Is NATO Deterrence a Paper Tiger? Judy Dempsey. Carnegie Europe, Jan 31 2019. https://carnegieeurope.eu/strategiceurope/78254

The same stale judgement of every single day:

Jan Techau. Senior fellow and director of the Europe Program at the German Marshal Fund of the United States
It increasingly seems so. Let’s leave the militarily weak Europeans aside for a moment. For NATO’s deterrence to be credible, only one question really matters: Is the United States fully behind its commitments? This depends on two factors. First, how much of a military footprint does the United States have in the countries it has vowed to defend? Only troops on the ground give real-life meaning to the stipulation that “an attack on one is an attack on all.” Second, how much confidence do the allies have in the U.S. president’s strategic reliability? The commander in chief matters because only he (or she) can commit troops to combat or trigger America’s nuclear arsenal.

The first metric is the smaller problem. America’s footprint in Europe is much smaller than it was twenty years ago. But Washington has recently reinvested in Europe; troop numbers are slightly up. It is the second factor that causes the headache. The current U.S. president has publicly questioned NATO’s usefulness and has had to be talked out of leaving the alliance altogether. Few people are convinced that he would go to war for Europe if need be. This lack of trust in Donald Trump is hugely corrosive for NATO’s credibility. It makes the allies nervous, and it emboldens the adversaries. Should Trump’s unreliability become a full certainty, NATO’s deterrent could soon look like a paper tiger indeed.

The reality:

Julian Lindley-French. Member of the George C. Marshall Centre-Munich Security Conference U.S.-German Loisach Group, senior fellow at the Institute for Statecraft in London, director of Europa Analytica in the Netherlands, Distinguished Visiting Research Fellow at the National Defense University in Washington, and a Fellow of the Canadian Global Affairs Institute

Paper tiger? No, more cardboard elephant. Thomas Schelling said that deterrence is the power to hurt as bargaining and best held in reserve. NATO has become a collective deterrent rather than a collective defender. On the eve of a short but violent war NATO would be the last place the Americans would turn to. Rather, as NATO continued to talk deterrence, Washington would put together a high-end coalition under its command to do the fighting.

NATO is too slow of thought, decision, and foot to fight a contemporary war. The conduct of war will become far faster with new technologies appearing in a battlespace that will stretch across air, sea, land, cyber, space, information, and knowledge. The Russians understand this and have built a thirty-day “wham, bam, thank you Vlad” war machine that would exploit NATO’s slowness of force generation and military mobility. NATO assumes at least thirty days of warning. Adaptation is thus buttressing deterrent value by accelerating NATO’s speed of response and extending its power to hurt.  NATO could fight a short war if it had the warning, or a long war if it was given the chance. Hmmm . . .

Old Dog, New Tricks: Age Differences in Dog Personality Traits, Associations with Human Personality Traits, and Links to Important Outcomes

Chopik, William J., and Jonathan R. Weaver. 2019. “Old Dog, New Tricks: Age Differences in Dog Personality Traits, Associations with Human Personality Traits, and Links to Important Outcomes.” PsyArXiv. February 1. doi:10.31234/osf.io/r3m4f

Abstract: Work examining dog personality is relatively new, so the degree to which dog personality differs by age, predicts important dog outcomes, and is correlated with human personality is unclear. In a sample of 1,681 dogs (Mage = 6.44 years, SD = 3.82; 46.2% Female; 50% purebred) and their owners, older dogs were less active/excitable compared to younger dogs. Aggression toward people, responsiveness to training, and aggression toward other animals was highest among 6 to 8 year old dogs. Dog personality was associated with important dog outcomes—chronic health conditions, biting history, and human-dog relationships. We build on previous research by examining demographic differences in dog personality and associations between dog personality and outcomes for both dogs and humans.

From 2012: Sexual Deprivation Increases Ethanol Intake in Drosophila

Sexual Deprivation Increases Ethanol Intake in Drosophila. G. Shohat-Ophir et al. Science Mar 16 2012: Vol. 335, Issue 6074, pp. 1351-1355. DOI: 10.1126/science.1215932

Abstract: The brain’s reward systems reinforce behaviors required for species survival, including sex, food consumption, and social interaction. Drugs of abuse co-opt these neural pathways, which can lead to addiction. Here, we used Drosophila melanogaster to investigate the relationship between natural and drug rewards. In males, mating increased, whereas sexual deprivation reduced, neuropeptide F (NPF) levels. Activation or inhibition of the NPF system in turn reduced or enhanced ethanol preference. These results thus link sexual experience, NPF system activity, and ethanol consumption. Artificial activation of NPF neurons was in itself rewarding and precluded the ability of ethanol to act as a reward. We propose that activity of the NPF–NPF receptor axis represents the state of the fly reward system and modifies behavior accordingly.

Children, especially girls, of gay fathers received significantly lower scores on internalizing (anxiety, depression) & externalizing (aggression, rule-breaking) than children in the comparison sample

Green, R.-J., Rubio, R. J., Rothblum, E. D., Bergman, K., & Katuzny, K. E. (2019). Gay fathers by surrogacy: Prejudice, parenting, and well-being of female and male children. Psychology of Sexual Orientation and Gender Diversity, http://dx.doi.org/10.1037/sgd0000325

Abstract: This research focused on behavioral functioning of children conceived via gestational surrogacy and raised by gay fathers. Gay fathers from 68 families with children aged 3–10 years completed the Achenbach Child Behavior Checklist. Their scores were compared to those from a normative sample of parents matched for parent’s occupation and children’s gender, age, and race/ethnicity. Children of gay fathers received significantly lower scores on internalizing (anxiety, depression) and externalizing (aggression, rule-breaking) than children in the comparison sample. Most notably, daughters of gay fathers had significantly lower internalizing scores than did daughters in the national database. Gay fathers also completed measures of parenting styles, social support, and perceived prejudice. Fathers who reported less authoritarian or permissive parenting, more positive coparenting, and more social support from friends had children with fewer behavior problems. Gay fathers’ reports of family members receiving higher levels of antigay microaggressions were associated with parents’ greater stigma consciousness, more anger/aggression from spouse/partner, and less positive parenting and coparenting. Results are discussed in terms of gay and heterosexual parents’ gender-related socialization of daughters’ internalizing problems and the impact of minority stress on same-sex couples’ parenting.

Facial disfigurement: Viewed significantly negatively in terms of personality (emotional stability, conscientiousness), internal attributes (happiness, intelligence), & social attributes (trustworthiness, popularity)

Jamrozik, A., Oraa Ali, M., Sarwer, D. B., & Chatterjee, A. (2019). More than skin deep: Judgments of individuals with facial disfigurement. Psychology of Aesthetics, Creativity, and the Arts, 13(1), 117-129. http://dx.doi.org/10.1037/aca0000147

Abstract: People’s physical appearance can have a profound impact on their social interactions. Faces are often the first thing we notice about people and the basis on which we form our first impressions of them. People with facial disfigurement are discriminated against throughout their lives. Currently, we do not know why this discrimination occurs. In order to develop viable interventions, we must first understand the nature of people’s reactions to disfigurement. In this work, we tested the hypothesis that a “disfigured is bad” stereotype exists, wherein people attribute negative characteristics to individuals with facial disfigurement. People made judgments of individuals before and after they received corrective treatment for their disfigurement. Observers reported lower emotional valence (i.e., more negative emotion), higher arousal, and lower dominance when viewing pretreatment (vs. posttreatment) photographs. Moreover, pictured pretreatment individuals were viewed significantly more negatively in terms of personality (e.g., emotional stability, conscientiousness), internal attributes (e.g., happiness, intelligence), and social attributes (e.g., trustworthiness, popularity). These subjective judgments further reduced to people with disfigurement being regarded as less sociable and happy, less dominant, less emotionally stable, and more as objects of curiosity compared with those with corrected facial disfigurement. Our findings suggest that negative stereotype of people with facial disfigurement may drive discrimination in social, academic, and professional contexts. Knowing what inferences people draw on the basis of disfigurement will make it possible to design interventions to improve the way people with disfigurement are viewed and ultimately treated by others.

Father absence, sociosexual orientation, and same‐sex sexuality in women and men

Father absence, sociosexual orientation, and same‐sex sexuality in women and men. Satoshi Kanazawa. International Journal of Psychology, https://doi.org/10.1002/ijop.12569

Abstract: A recent evolutionary theory of female sexual fluidity suggests that women may not have sexual orientations in the same sense that men do, and that women's apparent sexual orientation may instead be a byproduct of their sociosexual orientation. One developmental factor that has consistently been shown to influence sociosexual orientation is father absence in childhood. Consistent with the prediction of the theory, the analyses of the National Longitudinal Study of Adolescent to Adult Health (Add Health) data show that father absence significantly increases women's, but not men's, same‐sex sexuality in adulthood, whether it is measured by self identity, sexual behaviour, or romantic attraction. Further consistent with the theory, the association between father absence and same‐sex sexuality in women is entirely mediated by their sociosexual orientation.

Challenging anxious cognitions or accepting them? Efficacy of the cognitive elements of cognitive behaviour therapy & acceptance & commitment therapy in the reduction of children’s fear of the dark

Challenging anxious cognitions or accepting them? Exploring the efficacy of the cognitive elements ofcognitive behaviour therapy and acceptance and commitment therapy in the reduction of children’s fear of the dark. Ellin Simon et al. International Journal of Psychology, 2019. DOI: 10.1002/ijop.12540

Abstract: Anxiety is highly prevalent in pre-adolescent children. Distorted cognitions are characteristic for dysfunctional levelsof anxiety. However, applying cognitive elements in pre-adolescent children cannot be fully ascertained, as it is notuntil adolescence before children can apply logical and abstract reasoning in a sophisticated manner. Cognitive behaviour therapy (CBT) and acceptance and commitment therapy (ACT) both target distorted cognitions. Whereas CBT encourages children to change the content of negative cognitions by applying cognitive restructuring, ACT stimulates youth to have amore accepting attitude towards these thoughts by applying cognitive defusion. The current study examined the efficacy of applying cognitive elements and compared the cognitive elements of CBT and ACT in pre-adolescent children. Weincluded no behavioural elements to specifically study the developmental appropriateness of the cognitive elementsin this age group. Highly anxious children, aged 8–12 years were randomised to a 30-minute cognitive restructuring(n=21) or cognitive defusion intervention (n=22). Subjective fear of the dark levels, behavioural darkness toleration,and comprehension and fun associated with the interventions were assessed. Both interventions had a significantly positiveimpact on children’s fear of the dark. Cognitive restructuring led to more favourable results on subjective fear than cognitive defusion, no differences were found for darkness toleration.

Keywords: Child anxiety; Cognitive restructuring; Cognitive defusion; Fear of the dark; Pre-adolescence.

The Impact of the Affordable Care Act: Evidence from California's Hospital Sector: A substantial share of the federally-funded Medicaid expansion substituted for existing locally-funded safety net programs

The Impact of the Affordable Care Act: Evidence from California's Hospital Sector. Mark Duggan, Atul Gupta, Emilie Jackson. NBER Working Paper No. 25488, January 2019, https://www.nber.org/papers/w25488

Abstract: The Affordable Care Act (ACA) authorized the largest expansion of public health insurance in the U.S. since the mid-1960s. We exploit ACA-induced changes in the discontinuity in coverage at age 65 using a regression discontinuity based design to examine effects of the expansion on health insurance coverage, hospital use, and patient health. We then link these changes to effects on hospital finances. We show that a substantial share of the federally-funded Medicaid expansion substituted for existing locally-funded safety net programs. Despite this offset, the expansion produced a substantial increase in hospital revenue and profitability, with larger gains for government hospitals. On the benefits side, we do not detect significant improvements in patient health, although the expansion led to substantially greater hospital and emergency room use, and a reallocation of care from public to private and better-quality hospitals.

There is no advantage of second language on deliberate reasoning in the absence of time pressure; deliberation was not increased by providing items in a second language

Deliberate reasoning is not affected by language. Martin Jensen Mækelæ, Gerit Pfuhl. PLOS January 31, 2019. https://doi.org/10.1371/journal.pone.0211428

Abstract
Background: Millions of people use a second language every day. Does this have an effect on their decision-making? Are decisions in a second language more deliberate? Two mechanisms have been proposed: reduced emotionality or increased deliberation. Most studies so far used problems where both mechanisms could contribute to a foreign language effect. Here, we aimed to identify whether deliberate reasoning increases for problems that are devoid of any emotional connotation when using a second language or having to switch between native and second language.

Method: We measured deliberate reasoning with items from the cognitive reflection test, ratio bias, a probability matching task, and base rate neglect items. We recruited over 500 participants from Norway and the Netherlands that had English as their second language. Participants were randomly assigned to either the native, switching or second language condition. We measured: number of correctly answered items–deliberate reasoning score, perceived effort, perceived accuracy or confidence, and language proficiency.

Results: Deliberate reasoning was not increased when using a second language or when having to switch between native and second language. All three groups performed equally well. Significant predictors of deliberate reasoning were age, gender, education, perceived effort, and confidence but not the language context. Participants with low English proficiency spent more time reading compared to more fluent speakers.

Conclusion: There is no advantage of second language on deliberate reasoning in the absence of time pressure. Deliberation was not increased by providing items in a second language, but through the willingness to spend cognitive effort and time to read carefully.

Facebook deactivation reduced online activity & increased watching TV alone, socializing with family & friends; reduced factual news knowledge & political polarization; increased subjective well-being

The Welfare Effects of Social Media. Hunt Allcott, Luca Braghieri, Sarah Eichmeyer, and Matthew Gentzkow. January 27, 2019. http://web.stanford.edu/~gentzkow/research/facebook.pdf

Abstract: The rise of social media has provoked both optimism about potential societal benefits and concern about harms such as addiction, depression, and political polarization. We present a randomized evaluation of the welfare effects of Facebook, focusing on US users in the run-up to the 2018 midterm election. We measured the willingness-to-accept of 2,844 Facebook users to deactivate their Facebook accounts for four weeks, then randomly assigned a subset to actually do so in a way that we verified. Using a suite of outcomes from both surveys and direct measurement, we show that Facebook deactivation (i) reduced online activity, including other social media, while increasing offline activities such as watching TV alone and socializing with family and friends; (ii) reduced both factual news knowledge and political polarization; (iii) increased subjective well-being; and (iv) caused a large persistent reduction in Facebook use after the experiment. We use participants’ pre-experiment and post-experiment Facebook valuations to quantify the extent to which factors such as projection bias might cause people to overvalue Facebook, finding that the magnitude of any such biases is likely minor relative to the large consumer surplus that Facebook generates.

JEL Codes: D12, D90, I31, L86, O33.
Keywords: Social media, political polarization, subjective well-being, consumer surplus, projection bias.

The inflation expectations & perceptions of high-IQ men, but not others, are positively correlated over time; are also less likely to round and to forecast implausible values; & more likely to save for retirement

IQ, Expectations, and Choice. Francesco D’Acunto, Daniel Hoang, Maritta Paloviita, Michael Weber. NBER Working Paper No. 25496, January 2019. https://www.nber.org/papers/w25496

We use administrative and survey-based micro data to study the relationship between cognitive abilities (IQ), the formation of economic expectations, and the choices of a representative male population. Men above the median IQ (high-IQ men) display 50% lower forecast errors for inflation than other men. The inflation expectations and perceptions of high-IQ men, but not others, are positively correlated over time. High-IQ men are also less likely to round and to forecast implausible values. In terms of choice, only high-IQ men increase their propensity to consume when expecting higher inflation as the consumer Euler equation prescribes. High-IQ men are also forward-looking -- they are more likely to save for retirement conditional on saving. Education levels, income, socio-economic status, and employment status, although important, do not explain the variation in expectations and choice by IQ. Our results have implications for heterogeneous-beliefs models of household consumption, saving, and investment.

Biological Bases of Beauty Revisited: Increased masculinity is unattractive, but increased femininity is not; averageness & dimorphism yield relatively accurate predictions, but less important than believed

Jones, Alex L., and Bastian Jaeger. 2019. “Biological Bases of Beauty Revisited: The Effect of Symmetry, Averageness, and Sexual Dimorphism on Female Facial Attractiveness.” PsyArXiv. January 31. doi:10.31234/osf.io/xreu6

Abstract: The theoretical factors influencing human female facial attractiveness – symmetry, averageness, and sexual dimorphism – have been extensively studied. However, through improved methodologies, recent studies have called into question their links with life history and evolutionary utility. The current study uses a range of statistical and methodological approaches to quantify how important these factors actually are in perceiving attractiveness, through the use of novel analyses and by addressing methodological weaknesses inherent in the literature. Study One examines how manipulations of symmetry, averageness, femininity, and masculinity affect attractiveness using a two-alternative forced choice task, revealing that increased masculinity is unattractive, but increased femininity is not, and large effects observed for averageness. Study Two utilises a naturalistic ratings paradigm, finding similar effects of averageness and masculinity, but no effects of femininity and symmetry on attractiveness. Study Three applies a random forest machine learning algorithm and geometric measurements of the factors from faces to predict perceived attractiveness, finding that averageness and dimorphism are useful features capable of relatively accurate predictions. However, the factors do not explain as much variance in attractiveness as the wider literature suggests. Implications for future research on attractiveness are discussed.

The Influence of an Older Sibling on Preschoolers’ Lie‐telling Behavior

The Influence of an Older Sibling on Preschoolers’ Lie‐telling Behavior. Pooja Megha Nager, Shanna Williams, Victoria Talwar. Social Development, https://doi.org/10.1111/sode.12367

Abstract: In the present study, children's (2‐ to 5‐years old) lie‐telling was examined in relation to theory of mind (first‐order false belief understanding), executive functioning (measuring inhibitory control in conjunction with working memory), and presence of siblings (no siblings vs. siblings; younger siblings vs. older siblings) in the home. Lie‐telling was observed using a temptation resistance paradigm. Overall, of the 152 (74.9%) children who peeked at the toy, 73 (48.0%) lied during the temptation resistance paradigm. Children with higher scores on measures of first‐order false belief understanding, and measures that relied on inhibitory control, were more likely to lie compared to their truthful counterparts. Additionally, children with older siblings were more likely to lie to the research assistant, and this relationship was independent of performance on cognitive tasks. Overall, results demonstrate that having an older sibling has an independent, direct effect on the development of young children's lie‐telling abilities, irrespective of cognitive ability. These findings support the argument that lie‐telling is a behavior that is facilitated by both cognitive and social factors.

The Myers‐Briggs Type Indicator (MBTI) theory falters on rigorous theoretical criteria in that it lacks agreement with known facts & data, lacks testability, & possesses internal contradictions, but it is very popular

Evaluating the validity of Myers‐Briggs Type Indicator theory: A teaching tool and window into intuitive psychology. Randy Stein, Alexander B. Swan. Social and Personality Psychology Compass, https://doi.org/10.1111/spc3.12434

Abstract: Despite its immense popularity and impressive longevity, the Myers‐Briggs Type Indicator (MBTI) has existed in a parallel universe to social and personality psychology. Here, we seek to increase academic awareness of this incredibly popular idea and provide a novel teaching reference for its conceptual flaws. We focus on examining the validity of the Jungian‐based theory behind MBTI that specifies that people have a “true type” delineated across four dichotomies. We find that the MBTI theory falters on rigorous theoretical criteria in that it lacks agreement with known facts and data, lacks testability, and possesses internal contradictions. We further discuss what MBTI's continued popularity says about how the general public might evaluate scientific theories.

Do People Believe That They Are More Deontological Than Others?

Do People Believe That They Are More Deontological Than Others? Ming-Hui Li, Li-Lin Rao. Personality and Social Psychology Bulletin, https://doi.org/10.1177/0146167218823040

Abstract: The question of how we decide that someone else has done something wrong is at the heart of moral psychology. Little work has been done to investigate whether people believe that others’ moral judgment differs from their own in moral dilemmas. We conducted four experiments using various measures and diverse samples to demonstrate the self–other discrepancy in moral judgment. We found that (a) people were more deontological when they made moral judgments themselves than when they judged a stranger (Studies 1-4) and (b) a protected values (PVs) account outperformed an emotion account and a construal-level theory account in explaining this self–other discrepancy (Studies 3 and 4). We argued that the self–other discrepancy in moral judgment may serve as a protective mechanism co-evolving alongside the social exchange mechanism and may contribute to better understanding the obstacles preventing people from cooperation.

Keywords: moral judgment, self–other discrepancy, deontology, utilitarianism, protected values

Trying to “put yourself in their shoes” can ultimately undermine self-persuasion; effect is attenuated when people take the perspective of someone who holds the counterattitudinal view yet has similar overall values

Perspective Taking and Self-Persuasion: Why “Putting Yourself in Their Shoes” Reduces Openness to Attitude Change. Rhia Catapano, Zakary L. Tormala, Derek D. Rucker. Psychological Science, https://doi.org/10.1177/0956797618822697

Abstract: Counterattitudinal-argument generation is a powerful tool for opening people up to alternative views. On the basis of decades of research, it should be especially effective when people adopt the perspective of individuals who hold alternative views. In the current research, however, we found the opposite: In three preregistered experiments (total N = 2,734), we found that taking the perspective of someone who endorses a counterattitudinal view lowers receptiveness to that view and reduces attitude change following a counterattitudinal-argument-generation task. This ironic effect can be understood through value congruence: Individuals who take the opposition’s perspective generate arguments that are incongruent with their own values, which diminishes receptiveness and attitude change. Thus, trying to “put yourself in their shoes” can ultimately undermine self-persuasion. Consistent with a value-congruence account, this backfire effect is attenuated when people take the perspective of someone who holds the counterattitudinal view yet has similar overall values.

Keywords: attitude change, persuasion, perspective taking, receptiveness, resistance, open data, open materials, preregistered

h/t: Tyler Cowen, marginalrevolution.com

Contrastive paintings (paintings with high diversity of colors) carry a premium than equivalent artworks which are performed in monochromatic style

The impact of color palettes on the prices of paintings. Elena Stepanova. Empirical Economics, February 2019, Volume 56, Issue 2, pp 755–773. https://link.springer.com/article/10.1007/s00181-017-1413-4

Abstract: We emphasize that color composition is an important characteristic of a painting. It impacts the auction price of a painting, but it has never been considered in previous studies on art markets. By using Picasso’s paintings and paintings of Color Field Abstract Expressionists sold in Chrisite’s and Sotheby’s auctions in New York between 1998 and 2016, we demonstrate the method to analyze color compositions: How to extract color palettes from a painting image and how to measure color characteristics. We propose two measures: (1) the surface occupied by specific colors, (2) color diversity of a painting composition. Controlling for all conventional painting and sale characteristics, our empirical results find significant evidence of contrastive paintings, i.e., paintings with high diversity of colors, carrying a premium than equivalent artworks which are performed in monochromatic style. In the case of Picasso’s paintings, our econometric analysis shows that some colors are associated with high prices.

Keywords: Art markets Hedonic pricing Picasso Rothko Visual perception Color Color quantizing

In the juvenile period, primates form sex-differentiated bonds: females spend more time with female kin, & males with unrelated males; human males in middle childhood add, as chimpanzees do, intergroup contests

Sex Differences in Human Peer Relationships: A Primate’s-Eye View. Joyce F. Benenson. Current Directions in Psychological Science, https://doi.org/10.1177/0963721418812768

Abstract: Bonds formed by nonhuman animals can illuminate the structure of human relationships. In the juvenile period, primates of many species that are genetically similar to humans form sex-differentiated bonds in which females spend more time with female kin, and males spend more time with unrelated same-sex peers. Research with humans suggests a similar sex difference, with one notable addition: Beginning in middle childhood, male peer groups begin engaging in complex activities, including intergroup contests. This additional component of human peer relations resembles that of chimpanzees (Pan troglodytes), one of humans’ closest living genetic relatives. Cross-species and developmental evidence can aid in constructing a theory of human peer relations that differs by sex.

Keywords: peer relations, primates, sex differences, development