From 2019... In the U.S. and Côte d’Ivoire, highly educated people make decisions that are less consistent with the rational model while low-income respondents make decisions more consistent with the rational model

From 2019... Are We All Predictably Irrational? An Experimental Analysis. John A. Doces & Amy Wolaver. Political Behavior volume 43, pp1205–1226. Dec 18 2019. https://link.springer.com/article/10.1007/s11109-019-09579-0

Abstract: We examine the question of rationality, replicating two core experiments used to establish that people deviate from the rational actor model. Our analysis extends existing research to a developing country context. Based on our theoretical expectations, we test if respondents make decisions consistent with the rational actor framework. Experimental surveys were administered in Côte d’Ivoire and Ghana, two developing countries in West Africa, focusing on issues of risk aversion and framing. Findings indicate that respondents make decisions more consistent with the rational actor model than has been found in the developed world. Extending our analysis to test if the differences in responses are due to other demographic differences between the African samples and the United States, we replicated these experiments on a nationally representative analysis in the U.S., finding results primarily consistent with the seminal findings of irrationality. In the U.S. and Côte d’Ivoire, highly educated people make decisions that are less consistent with the rational model while low-income respondents make decisions more consistent with the rational model. The degree to which people are irrational thus is contextual, possibly western, and not nearly as universal as has been concluded.

Introduction

Are we all predictably irrational? Since the seminal work of Tversky and Kahneman (1974, 1981, 1986, 1991) and other behavioral economists (Akerlof and Kranton 2000; Ariely 2010; Camerer 2003; Thaler 1980), the usefulness of models assuming rationality has been questioned, if not entirely dismissed in some cases (Green and Shapiro 1994; Sen 1977). However, the vast majority of the empirical work establishing consistently irrational behaviors has been conducted on populations in the West, dubbed WEIRD for Western, educated, industrialized, rich and democratic (Henrich et al. 2010). In their review of the psychology literature, Henrich et al. (2010) indicate that 68% of subjects were from the United States, 96% from the Western Industrialized world, with 80% of the Western sample being undergraduate students. If other populations behave differently than these groups, then the implications of the new models of behavior may not be as widely applicable as we thought.

There have been some forays examining deviations from the predictions based on the rational actor model across different populations, notably studies of the impact that poverty has on decision-making. While some studies establish ways in which poverty decreases cognitive ability through the additional stresses associated with living in poverty (Mani et al. 2013; Haushofer and Fehr 2014), others argue that the influence of poverty on decisions is related more to additional constraints and a constant presence of risk in the lives of the poor (Duflo 2006; Banerjee and Duflo 2007; Carvalho et al. 2016). There is a growing body of literature that establishes that the poor are less subject to some of the cognitive biases found by Tversky and Kahneman (Shah et al. 2015, 2018). Possible explanations for the differences in decision-making by the poor are that poverty may increase attention to costs, and/or it exposes one to more risk, which causes people to give more weight to current versus future outcomes.

To determine whether these predictable irrationalities are applicable in other parts of the world, we replicate some of the most important experiments conducted by Tversky and Kahneman (1981) in Côte d’Ivoire and Ghana, and compare these samples to those from Western populations. We find that respondents from Côte d’Ivoire and Ghana make decisions that are closer to the model of rationality than Westerners. Building on this key finding, we also examine the effects of individual characteristics on decision-making to determine whether there are systematic differences within these populations. Here, we find that most sub-groups, with some exceptions, make decisions that are relatively more consistent with the predictions of the rational model than has been found in prior research. Finally, to ascertain why the differences exist between the original results from 1981 and our data, we re-consider two of the original experiments in a nationally representative sample of American adults. This sample provides support for the 1981 results of systematic irrationality, with important exceptions, and helps to contrast our findings from West Africa that the rational actor model is most applicable in the developing world.

Our empirical results, in sum, suggest there is more merit to the rational choice paradigm than perhaps has been thought, and that existing studies concluding people are predictably irrational are overstated in a number of ways. This is an important finding with implications for several areas of academic scholarship. The rational actor model has served as the cornerstone assumption about the behavior of political actors, influencing research in political science on voter choice, foreign policy making, conflict, and international political economy amongst others (de Mesquita and Smith 2011; Mansfield et al. 2000; Powell 1991; Slantchev and Tarar 2011). Recent work has extended the paradigm to explicitly non-western contexts (Hollyer et al. 2015). Nevertheless, debates about its utility in political science have been especially spirited (de Mesquita and Morrow 1999; Walt 1999), with one enduring criticism being the lack of empirical support that people behave as the model assumes, a point which even supporters acknowledge (Kahler 1998; Snidal 2002). In economics, as well, the core mainstream model assumes rationality, with applications to the law (Posner 2014) and even addiction (Becker et al. 1991). By addressing the empirical underpinnings of rational choice, we help fill an important gap in our understanding of rationality and show that the model might be most relevant for non-western populations.

Uncommon case of complete loss of hunger following an isolated left insular stroke

Uncommon case of complete loss of hunger following an isolated left insular stroke. Benjamin Hébert-Seropian, Olivier Boucher, Didier Jutras-Aswad & Dang Khoa Nguyen. The Neural Basis of Cognition, Aug 16 2021. https://doi.org/10.1080/13554794.2021.1966044

Abstract: The insula has long been among the least understood regions of the human brain, in part due to its restricted accessibility. Mounting evidence suggests that the insula is a prominent player in gustatory, interoceptive, and emotional processing, and likely integrates these different functions to contribute to the homeostatic control of food intake. Here we report the case of a young adult patient who lost the subjective experience of hunger following an ischemic stroke localized in the posterior left insula. The loss of hunger was not attributable to medication, substance use, or a clinical disorder, and lasted for a period of 15 months. In line with the role attributed to the insula in gustation and interoception, we suggest that the insula integrates information about taste, interoception, and the hedonic value of food in the service of homeostatic regulation.

KEYWORDS: Hungerappetiteinsulastrokecase report

Found some evidence that higher income is associated with less happiness and no substantive benefit to higher household income in the US after $35-40K and in Germany after €14-18K (in daily life, not as an assessment of the whole)

Kudrna, Laura, and Kostadin Kushlev. 2021. “Money Does Not Always Buy Happiness, but Are Richer People Less Happy in Their Daily Lives? It Depends on How You Analyze Income.” PsyArXiv. August 18. doi:10.31234/osf.io/4jvh5

Abstract: Do people who have more money feel happier during their daily activities? Some prior research has found no relationship between income and daily happiness when treating income as a continuous variable in OLS regressions, although results differ between studies. We re-analyzed existing data, treating household income as a categorical variable and using lowess and spline regressions to explore non-linearities. Our analyses reveal that these methodological decisions provide new insights into the relationship between income and happiness. We find some evidence that higher income is associated with less happiness and no substantive benefit to higher household income in the US after $35-40K and in Germany after €14-18K. Not all analytic approaches generate the same conclusions, which may explain discrepant results.

From 2019... Greater male cognitive variability has implications for both tails of the distribution: Danish data (n = 1.3 million) finds that twice as many boys than girls are diagnosed with intellectual disability

From 2019... Incidence Rates and Cumulative Incidences of the Full Spectrum of Diagnosed Mental Disorders in Childhood and Adolescence. Søren Dalsgaard et al. JAMA Psychiatry. 2020;77(2):155-164. Nov 20, 2019, doi:10.1001/jamapsychia

Key Points

Question  What are the age- and sex-specific incidence rates and cumulative incidences of the full spectrum of diagnosed mental disorders during childhood and adolescence?

Findings  In this nationwide cohort study of 1.3 million individuals in Denmark, the risk (cumulative incidence) of being diagnosed with a mental disorder before 18 years of age was 14.63% in girls and 15.51% in boys. Distinct age- and sex-specific patterns of occurrence were found across mental disorders in children and adolescents.

Meaning  These findings suggest that precise estimates of rates and risks of all mental disorders during childhood and adolescence are essential for future planning of services and care and for etiological research.

Abstract

Importance: Knowledge about the epidemiology of mental disorders in children and adolescents is essential for research and planning of health services. Surveys can provide prevalence rates, whereas population-based registers are instrumental to obtain precise estimates of incidence rates and risks.

Objective  To estimate age- and sex-specific incidence rates and risks of being diagnosed with any mental disorder during childhood and adolescence.

Design  This cohort study included all individuals born in Denmark from January 1, 1995, through December 31, 2016 (1.3 million), and followed up from birth until December 31, 2016, or the date of death, emigration, disappearance, or diagnosis of 1 of the mental disorders examined (14.4 million person-years of follow-up). Data were analyzed from September 14, 2018, through June 11, 2019.

Exposures: Age and sex.

Main Outcomes and Measures  Incidence rates and cumulative incidences of all mental disorders according to the ICD-10 Classification of Mental and Behavioral Disorders: Diagnostic Criteria for Research, diagnosed before 18 years of age during the study period.

Results  A total of 99 926 individuals (15.01%; 95% CI, 14.98%-15.17%), including 41 350 girls (14.63%; 95% CI, 14.48%-14.77%) and 58 576 boys (15.51%; 95% CI, 15.18%-15.84%), were diagnosed with a mental disorder before 18 years of age. Anxiety disorder was the most common diagnosis in girls (7.85%; 95% CI, 7.74%-7.97%); attention-deficit/hyperactivity disorder (ADHD) was the most common in boys (5.90%; 95% CI, 5.76%-6.03%). Girls had a higher risk than boys of schizophrenia (0.76% [95% CI, 0.72%-0.80%] vs 0.48% [95% CI, 0.39%-0.59%]), obsessive-compulsive disorder (0.96% [95% CI, 0.92%-1.00%] vs 0.63% [95% CI, 0.56%-0.72%]), and mood disorders (2.54% [95% CI, 2.47%-2.61%] vs 1.10% [95% CI, 0.84%-1.21%]). Incidence peaked earlier in boys than girls in ADHD (8 vs 17 years of age), intellectual disability (5 vs 14 years of age), and other developmental disorders (5 vs 16 years of age). The overall risk of being diagnosed with a mental disorder before 6 years of age was 2.13% (95% CI, 2.11%-2.16%) and was higher in boys (2.78% [95% CI, 2.44%-3.15%]) than in girls (1.45% [95% CI, 1.42%-1.49%]).

Conclusions and Relevance  This nationwide population-based cohort study provides a first comprehensive assessment of the incidence and risks of mental disorders in childhood and adolescence. By 18 years of age, 15.01% of children and adolescents in this study were diagnosed with a mental disorder. The incidence of several neurodevelopmental disorders peaked in late adolescence in girls, suggesting possible delayed detection. The distinct signatures of the different mental disorders with respect to sex and age may have important implications for service planning and etiological research.

Check also Greater male variability is currently universal in internationally comparable assessments; some of this heterogeneity can be attributed to some species universal mechanism or some other social/cultural phenomenon

Sex differences in variability across nations in reading, mathematics and science: a meta-analytic extension of Baye and Monseur (2016). Helen Gray, Andrew Lyth, Catherine McKenna, Susan Stothard, Peter Tymms and Lee Copping. Large-scale Assessments in EducationAn IEA-ETS Research Institute Journal 20197:2. https://www.bipartisanalliance.com/2019/03/greater-male-variability-is-currently.html

Faecal transplants from young mice can enhance cognitive function in older animals

Microbiota from young mice counteracts selective age-associated behavioral deficits. Marcus Boehme et al. Nature Aging volume 1, pages666–676. Aug 9 2021. https://www.nature.com/articles/s43587-021-00093-9

Abstract: The gut microbiota is increasingly recognized as an important regulator of host immunity and brain health. The aging process yields dramatic alterations in the microbiota, which is linked to poorer health and frailty in elderly populations. However, there is limited evidence for a mechanistic role of the gut microbiota in brain health and neuroimmunity during aging processes. Therefore, we conducted fecal microbiota transplantation from either young (3–4 months) or old (19–20 months) donor mice into aged recipient mice (19–20 months). Transplant of a microbiota from young donors reversed aging-associated differences in peripheral and brain immunity, as well as the hippocampal metabolome and transcriptome of aging recipient mice. Finally, the young donor-derived microbiota attenuated selective age-associated impairments in cognitive behavior when transplanted into an aged host. Our results reveal that the microbiome may be a suitable therapeutic target to promote healthy aging.

Popular version: Faecal transplants from young mice can enhance cognitive function in older animals. https://www.nature.com/articles/d41586-021-02184-4

Challenging the binary: Gender/sex and the bio-logics of normalcy

Challenging the binary: Gender/sex and the bio-logics of normalcy. L. Zachary DuBois, Heather Shattuck-Heidorn. American Journal of Human Biology, June 6 2021. https://doi.org/10.1002/ajhb.23623

Abstract

Background: We are witnessing renewed debates regarding definitions and boundaries of human gender/sex, where lines of genetics, gonadal hormones, and secondary sex characteristics are drawn to defend strict binary categorizations, with attendant implications for the acceptability and limits of gender identity and diversity.

Aims: Many argue for the need to recognize the entanglement of gender/sex in humans and the myriad ways that gender experience becomes biology; translating this theory into practice in human biology research is essential. Biological anthropology is well poised to contribute to these societal conversations and debates. To do this effectively, a reconsideration of our own conceptions of gender/sex, gender identity, and sexuality is necessary.

Methods: In this article, we discuss biological variation associated with gender/sex and propose ways forward to ensure we are engaging with gender/sex diversity. We base our analysis in the concept of “biological normalcy,” which allows consideration of the relationships between statistical distributions and normative views. We address the problematic reliance on binary categories, the utilization of group means to represent typical biologies, and document ways in which binary norms reinforce stigma and inequality regarding gender/sex, gender identity, and sexuality.

Discussion and Conclusions: We conclude with guidelines and methodological suggestions for how to engage gender/sex and gender identity in research. Our goal is to contribute a framework that all human biologists can use, not just those who work with gender or sexually diverse populations. We hope that in bringing this perspective to bear in human biology, that novel ideas and applications will emerge from within our own discipline.

1 | INTRODUCTION

Biological anthropologists are experts at teasing apart the complexities of biocultural interactions that inform what it is to be human, examining how broad-ranging factors such as market acculturation (Godoy et al., 2005; Liebert et al., 2013), parenting strategies (McKenna et al., 2007; Nelson, 2016), or socially constructed categories of race (Dressler & Bindon, 2000; Gravlee, 2009) relate to physiology including growth and development, immune function, and endocrinology. Yet we have not fully engaged with cutting-edge understandings of variation in gender, sex, and sexuality. This is a critical gap, especially given renewed debates regarding the boundaries of human sex, where lines of genetics, “sex hormones,” and secondary sex characteristics are drawn to defend a strict biologically based sex binary, with attendant implications for the acceptability and limits of gender identity and expression for all people. Whether regulating testosterone levels and bodies of women and girls in sports, legislating the use of gender-specific bathrooms, or enacting broadsweeping federal definitions of sex, bodily “norms” are being weaponized as a means to discriminate (Karkazis et al., 2012; Nondiscrimination in Health and Health Education or Activities, 2020). Biological anthropology is well poised to contribute to these societal conversations, but first, we need to more deeply consider our own conceptions of sex, gender, and sexuality, and how we implement such understandings in our research. In this article, we discuss biological variation associated with sex and gender and possible ways forward for conceptualizing and operationalizing these constructs within biological anthropology. We base our analysis in the concept of “biological normalcy,” which allows consideration of the relationships between “statistical distributions of biological traits and normative views about what bodies ‘should’ be like or what constitutes a ‘normal’ body” (Wiley & Cullin, 2020: p. 1; Wiley, 2021). A classic example of how bionormalcy enables critical interrogation of norms is seen in the case of dietary recommendations normalizing milk consumption culturally as “healthy” and even necessary, despite the statistical norm of lactase nonpersistence (Wiley, 2021). This can be seen as normalizing and even moralizing a biological trait present only in some individuals in some populations (Wiley & Allen, 2017; Wiley & Cullin, 2020). This example aptly demonstrates the fact that many of the statistical distributions that end up being “normalized” are based on samples drawn from predominantly white, “Western” populations (Clancy & Davis, 2019; Henrich et al., 2010), with the psychological, behavioral, and biological traits of these populations referenced as the standard from which other populations deviate (e.g., body size and growth, Thompson et al., 2014). The model of biological normalcy (Figure 1) is circular. Cultural norms and assumptions inform the development of research questions, methods of data collection, and analyses as well as interpretations of data. Statistical norms are also leveraged (albeit sometimes unconsciously) to create, reinforce, or otherwise inform those very cultural norms and assumptions. However, normalcy has not always been conceptualized in this way. The word “normal” as reflective of something to be desired in reference to an “abnormal” state arose only in the mid to late 19th century (Cryle & Stephens, 2017; Hacking, 1990). Initially, the term “normal” did not represent statistical distributions nor did it carry the morality it is imbued with today. Instead, norms provided a way to reference something “in its own right” and not necessarily through comparison to an ideal. In this way, even anomalies could be understood within a framework of “normal.” With the emergence of statistics in the late 19th century, the concept of the normal became hitched to statistical distributions and to the racist and eugenicist ideas imposed on population traits (Cryle & Stephens, 2017). And with this shift, the concept of the normal intertwines with the history of biological anthropology, as eugenic and white supremacist concepts of human traits and the categorical position of white men as both unmarked and ideal are the very foundation of much of our field (Blakey, 2020; Caspari, 2018; Marks, 2012). Racism and colonialism are equally culpable in the development of value-laden categories of sex and gender and the behavioral norms to which they are often tied. For example, conceptualizations of femininity and masculinity themselves were initially intertwined with racialized categories in an effort to hierarchically demarcate rank, reflecting a colonialist project with the “white ideal” as most differentiated between the sexes (Markowitz, 2001). As a field, biological anthropology continues to suffer from how our history influences who practices biological anthropology (e.g., Bolnick et al., 2019). As biocultural anthropologists, in this article, we aim to broaden the way that human biology engages with categorical thinking about gender and sex and to push for greater recognition of variation in these domains. We are inspired by the decades of strong work into race as a social construct with biological outcomes (Armelagos & Goodman, 1998; Dressler et al., 2005; Graves Jr, 2003; Graves Jr, 2015; Gravlee, 2009; Williams & Mohammed, 2013), and by recent work contextualizing how concepts such as violence are gendered and raced (e.g., Nelson, 2021; Smith, 2021). In our own work, we have grappled with how to better conceptualize and operationalize sex and gender, whether examining energetics and immune function in pubertal girls (ShattuckHeidorn, Reiches, & Richardson, 2020), sexual decision making among queer adolescent cis men (DuBoiset al., 2015), or immune marker and environmental conditions for (cis) men and women (Shattuck-Heidorn, Eick, et al., 2020). In some of our prior work, the category “cis” was unmarked, and at times, in our analytical strategies, we have statistically compared cis men to cis women without a clear justification as to why the sample should be divided by sex as opposed to some other trait(s). Much of our recent scholarship integrates theoretical insights from gender and feminist theory and presents challenges to simple gender/sex binaries through our research questions, study designs, and hypotheses. This is reflected for example, in work expanding understandings of stigma and embodied inequalities among trans and gender diverse people (DuBois, 2012; DuBois et al., 2017), furthering our methodological and theoretical approaches to better encompass gender/sex and sexual diversity (DuBois et al., 2021; Shattuck-Heidorn & Richardson, 2019), and interrogations into the basis for disparities in COVID-19 outcomes (Gibb et al., 2020; Rushovich et al., 2021; Shattuck-Heidorn, Reiches, & Richardson, 2020). Such interdisciplinary merging has enabled us to better conceptualize human gender/sex and enhanced our understanding of variation in embodiment and health. In this article, we address the following critical areas: (1) the problematic reliance on binary sex categories used as a priori biological categories across traits; (2) the attendant focus on group means to represent typical “male” and “female” behaviors and biology and accompanying fixation on “difference;” (3) the ways in which binary sex norms reinforce stigma and inequality regarding sex, gender, gender identity, and sexuality; (4) the need for “best practices” to effectively engage sex and gender in research; and (5) methodological suggestions to address the lack of inclusive data collection needed to enhance our understanding of gender and sex and sexual variation. Our goal is to contribute to a framework that all human biology researchers, not just those who work with gender or sexually diverse populations, can use to inform their thinking as well as decisions about best practices for whether and how to implement sex and gender analyses within their research, both theoretically and methodologically.

6 | CONCLUSIONS

As human biologists, gender/sex is central to how we understand and organize our thinking about human evolution as well as health in contemporary and historic contexts. The entwinement of gender and sex is complex, as is much of the science exploring this variation and how it develops. It is increasingly necessary for human biologists to engage novel methodologies to ensure we are capturing and engaging with gender/sex diversity. As detailed above, research in human biology and other disciplines challenges the understanding and the use of binary sex as a meaningful category explaining human biological variation across contexts. The work reviewed here is a small part of a large field of research that pushes us to continue to consider the ways in which human bodies and identities resist static categorization. Hormones vary and function in complex ecological and social environments, brains and bodies develop over time in response to varied experiences and inputs, and societal structures of gender norms, race and racism, and sexuality influence and mediate human biology. As the common-sense notion of binary categories for human gender/sex are destabilized, our discipline is well-positioned to meaningfully explore the complexity of gender/sex in terms of human variation and to understand that variation within a sociocultural context, including race, sexuality, and gender diversity. Our field has contributed substantially to an understanding of human biology in a socioecological context. We look forward to a generation of work from biological anthropologists who are incorporating intersectional analyses of gender/sex and gender identity into our understandings of human diversity.

Population affinity and variation of sexual dimorphism in three-dimensional facial forms: comparisons between Turkish and Japanese populations

Population affinity and variation of sexual dimorphism in three-dimensional facial forms: comparisons between Turkish and Japanese populations. Chihiro Tanikawa, M. Okan Akcam, Hatice Gokalp, Edlira Zere & Kenji Takada. Scientific Reports volume 11, Article number: 16634. Aug 17 2021. https://www.nature.com/articles/s41598-021-96029-9

Abstract: Examining the extent to which sex differences in three-dimensional (3D) facial soft tissue configurations are similar across diverse populations could suggest the source of the indirect evolutionary benefits of facial sexual dimorphism traits. To explore this idea, we selected two geographically distinct populations. Three-dimensional model faces were derived from 272 Turkish and Japanese men and women; their facial morphologies were evaluated using landmark and surface-based analyses. We found four common facial features related to sexual dimorphism. Both Turkish and Japanese females had a shorter lower face height, a flatter forehead, greater sagittal cheek protrusion in the infraorbital region but less prominence of the cheek in the parotid-masseteric region, and an antero-posteriorly smaller nose when compared with their male counterparts. The results indicated the possible phylogenetic contribution of the masticatory organ function and morphogenesis on sexual dimorphism of the human face in addition to previously reported biological and psychological characteristics, including sexual maturity, reproductive potential, mating success, general health, immune response, age, and personality.

Discussion

In the present study, principal components that explained 66.2% of the sample’s variance showed interaction between population affinity and sex were not significant, which indicates that both populations have statistically similar expressions of sexual dimorphism. Alternatively, our detailed analysis revealed that both population affinity characteristics of facial sexual dimorphism that were common to both the Japanese and Turkish subjects, and some characteristics that were unique to each set of subjects. The presence of both similarities and differences in facial sexual dimorphism among populations described in this study were consistent with previous controversial studies regarding population affinity9,10,11,12. The common characteristics could have arisen from a strong selective force on fundamental function to survive as a result of natural selection, and the differing sexually dimorphic characteristics could be due to environmental adaptation under a trade-off between natural and sexual selection22.

Regarding the common sexual dimorphic characteristics, both the Japanese and Turkish females had a shorter face height, especially with regard to the lower face; a flatter forehead; greater sagittal cheek protrusion in the posterior part of the infraorbital region; and less prominence of the cheek in the parotid-masseteric region. Furthermore, females in both population groups had antero-posteriorly smaller noses and greater retrusion of the columella base and subnasal region.

Males showed a greater height in the lower anterior face, especially with regard to the chin, in both population groups. It should be noted that a previous cephalometric study23 documented temporal changes in the ratios of the anterior lower face height to the total face height in the Japanese population. Females exhibited the anterior lower face height to total face height ratio almost equal to or longer than males at 6, 8, and 10 years old. Females at 6, 10, and 14 years old had lower face height ratios that were similar to those of adults (6 years old = 54.6% and adults = 54.9%). It is after 12 years of age when males begin to have increased face height ratio23. The observed increase in the lower anterior face height in males can be ascribed to sexual differences in pubertal growth potential of the mandible23, which is prolonged in males compared with females. There are several explanations regarding why men have a greater lower anterior face height, especially in the chin after pubertal growth. From the perspective of mastication, it seems likely that the acquired basic skill for most fundamental motor performance, such as mastication and locomotion, is independent of sex24. A previous study25 documented that the smoothness or skillfulness of masticatory jaw movement in terms of minimizing the jerk cost is not sex-specific. It should, however, also be noted that some parameters, such as the amount of jaw opening and movement velocity, are sensitive to sex-specific differences in jaw size and masticatory muscle properties25. Adult females show longer duration and lower peak velocity in masticatory jaw movement compared with males24; this can be ascribed to adult males generating greater muscle force and faster muscle contraction26 with greater muscle volume and size of the mandible, to which the jaw-closing muscles are attached. Sex influences on maximal molar bite force and masticatory muscle thickness17. Thus, the anatomy and function of the masticatory muscles may contribute to explaining why males generally have greater faces, especially in the lower third.

Furthermore, the allometric decomposition findings concerning sexual shape dimorphism support the phylogenetic importance of the chewing apparatus in sexual dimorphism in males. As men require more calories than women to function16, it is reasonable that their greater body size tends to correlate with a greater anterior facial height for a well-developed chewing apparatus. A previous study that examined 2D allometric and non-allometric variation in the facial shape differences between men and women showed a rather weak link with allometric variation compared with non-allometric variation in most populations, including the Turkish. As our study showed that the allometric difference was greater than non-allometric differences, this is considered to be related to the sex differences in the antero-posterior direction.

From a biological perspective, sex hormones are major factors related to sexual dimorphism. In males, higher androgen serum levels at puberty exert potent osteoanabolic effects and therefore may contribute to this skeletal sexual dimorphism. Animal experiments with anabolic steroids demonstrated a clear effect on craniofacial growth, mainly as an increase in total skull length and increase in the depth of the antegonial notch27. Interestingly, a previous study showed that mandibular and cortical human osteoblastic cells of both sexes expressed higher androgen receptor mRNA levels and significantly more androgen binding sites per cell and exhibited significantly greater mitogenic responses to the androgen dihydrotestosterone28. Those results indicate that the vertically greater mandibular height in males observed in our study could be due to skeletal site-dependent expression of the androgen receptor in the mandible. Additionally, a previous study that examined facial morphology of 1-year-old boys and girls showed the existence of early sexual dimorphism, and prenatal testosterone exposure is thought to be related to sexually dimorphic facial morphology29. Thus, it is possible that androgens in males could contribute to facial sexual dimorphism both before and after puberty.

Previous studies on anthropoids revealed only smaller muscle strains in the supraorbital region in contrast to those in the infraorbital region or the zygomatic arch during mastication30,31. Animal studies32,33 have also revealed that circumorbital structures became greater to provide rigidity against non-masticatory forces; these studies revealed that is unlikely that masticatory muscle forces contributed to the remodeling of the supraorbital torus. On the contrary, the development of the supraorbital ridge has been viewed as an ontogenetic adaptation to masticatory forces34. In primates, masticatory-stress models have been examined using in vivo experimental data. Primates have significant temporalis attachments that extend to almost the midline of the frontal bones; bending of the brow-ridges is thought to be due to the mastication force pushing upward and the masseter and temporalis muscles pulling downward35. Few of the previous computational models, using finite element analysis of primate skulls36, agree with these in vivo findings. A previous study37 found a positive correlation between the mesio-distal crown width of the mandibular first molar and the size of the supraorbital ridge in humans. Occlusal forces exerted on the molar teeth contribute to supraorbital torus formation. Because females generate weaker muscle force and slower muscle contraction than males26, and exhibit decreased maximal molar bite force and masticatory muscle thickness17, we should not rule out the possibility of contribution of masticatory muscle forces to supraorbital ridge formation in humans. Phylogenetically, the smaller supraorbital ridge observed in the female subjects in the present study may be explained by the differences in masticatory force magnitude and its relevant jaw muscle thickness between males and females17,30.

In the present study, both Japanese and Turkish males showed an antero-posteriorly greater nose when the eye distances were standardized. This result is in line with those of previous studies38,39,40. Previous studies primarily hypothesized that males have evolved to have greater nasal cavity dimensions to facilitate the oxygen intake that is needed to maintain a larger body mass37,41. The degree of sexual dimorphism in nasal shape is considered to be potentially due to the functional integration between the nasal cavity and the respiratory system42.

The extent of the cheek region is defined as “superiorly to the zygomatic arch, inferiorly to the margin of the mandible, posteriorly to the ear, and anteriorly to the corner of the mouth” and is divided into four parts as topographical regions: infra-orbital, buccal, zygomatic, and parotid–masseteric regions43).

In the present study, in the infraorbital and buccal regions, the sagittal cheek protrusion in the posterior part of the infraorbital region was greater in the female subjects on the left side. Furthermore, lesser prominence of the cheek in the parotid–masseteric region was also observed in both Japanese and Turkish female subjects.

A lesser prominence of the cheek in the parotid–masseteric region can be explained by the smaller masseter muscles in women17. Thin masseter muscles lead to a lesser prominence of the cheek in the parotid–masseteric region in women.

Effects of developmental and functional interactions on morphological variability of the head through ontogeny have been discussed in previous studies42,44. Several studies42,44 have claimed that genetic signals determine the initial geometry of craniofacial anatomy, and that geometry is altered by the local mechanical environment, such as masticatory function and respiratory function, through variations in the spatio-temporal interplay of depository and resorptive activity of bone. In contrast, there is very little concrete evidence of the relationship between functional and phylogenetic development in facial configurations. In general, it is assumed that varying environmental conditions, such as climates, geographic areas, and dietary resources, require physical characteristics, including dento-facial features, which contribute to maximizing the survival probability of individuals. Hominids are now recognized as showing higher adaptability to their surrounding environment based on related morphological changes than was previously understood.

In the past, several studies have addressed 3D morphological differences between populations. For example, between Caucasians and African-Americans, the most distinct differences were observed in the forehead, alar base, and perioricular regions using 3D facial data45; between Caucasians and Asians, differences were observed in the malar and zygomatic areas, forehead, lips, and chin46. Even in the phylogenetically related populations, there were differences seen in the nasal, malar, lips, and lower facial regions between two population groups (Budapest, Hungary, and Houston, Tex)47; differences were also observed in the nasal width, eye distances, and facial height of two European Caucasian populations of close phylogenetic and geographic proximity (UK and Netherlands)14. In short, the previous studies described the facial differences between the population groups; however, limited data has been reported regarding varied facial sexual dimorphic characteristics among populations.

In the present study, four features in the Japanese and three in the Turkish were found to be exclusive sexual dimorphic characteristics. In the Japanese subjects, females had greater eye height (i.e., brighter eyes) compared with males. A medium or high upper eyelid crease is known to represent an attractive face in East Asian females, and 50% of females exhibit a minimal or absence of a double eyelid44. Although greater eye height is also deemed an important factor for facial attractiveness in other populations, the present results indicate that eye height is a visible facial sexual dimorphism that is more discriminatory in the Japanese subjects than the Turkish subjects.

Japanese females also showed a smaller anteroposterior protrusion of the nasal dorsum at the orbital level (i.e., a flatter nose) and a superiorly positioned mouth with a vertically shorter subnasal region. Additionally, shorter horizontal mandibular width was observed in the Japanese females. These findings indicate that Japanese females had overall smaller middle and lower facial structures than males. In a previous study that examined the 3D nasal shape and genotype in 3746 individuals, nares width was correlated with temperature and absolute humidity48. This result indicates that at least sexual dimorphism in nasal shape may change because of climate adaptation.

In contrast to the Japanese females, three features were found to be characteristic of the Turkish females compared with Turkish males. There was a greater vertical distance between the eyes and eyebrows, and an increased zygomatic width compared with exocanthion–exocanthion distance. These traits reflect a stout upper facial structure. Facial ontogeny research on immature hominids with a finite element model49 showed that bone deposition was identified over the outer aspects of the orbits, lateral nasal walls, infraorbital region, zygomatico-maxillary region, parts of the mid-clivus, including the canine jugum, and interincisal protuberance, as well as portions of the nasal sill and areas lateral to the intermaxillary suture; they inferred that these changes were related to the masticatory system49.

A shallower labio-mental sulcus also characterized Turkish female compared with male faces. A recent study39 indicated that an ontogenetic decrease in chin prominence was associated with increased vertical bending resistance and vice versa. Thus, it can be inferred that a shallow labiomental sulcus was unique to the current Turkish female participants, which indicates an adaptational response of Turkish females, who have delicately constituted jaw bones and muscles, compared with Turkish males in a dietary environment that includes tougher animal proteins compared with the Japanese dietary environment.

It is well known that Africa is the ancestral homeland of modern humans50. A phylogenetic tree showed the categorization of the world population into nine sub-populations based on the polymorphisms of protein genes of 1915 populations: African; North African and West Asian; European; Amerind; Arctic Northeast Asian; Northeast Asian; Southeast Asian; Pacific Islander; and New Guinean and Australian51. The genetic distances between Japanese (Northeast Asian) and Turkish (European) were moderately far (55% of total distance) whereas European and North African were close (7%); this indicated that Japanese and Turkish (European) had different developmental route51. Genetic data also provided some indication that the spread of humans into Asia was along the coast to south and south-east Asia, from where it bifurcated to the north and south52. Thus, our comparisons of sexual dimorphism in facial forms between Turkish and Japanese populations can explain a relatively long span of genetic drift, which is the result of population variation among individual genotypes in their probabilities of survival and/or reproduction.

Several limitations associated with the present study warrant mention. First, the Turkish population was undersampled in comparison to the Japanese population. The frontal view of our 3D Turkish data was similar to that of a previous 2D study53 which used a greater number of Turkish samples (n = 264); thus it could be said that our results are possibly representative of the Turkish population. However, future studies including more Turkish subjects would us to make more general conclusions. Second, our study included only two populations, so it is impossible to draw complex conclusions regarding the geographical variability of the human face. Future studies would benefit from including an even larger number of populations. Third, in the present study, we used only the centroid size of the face to examine the allometric component. The results may vary when using the height or weight. Furthermore, in the present study, we omitted color information when analyzing the data because this information was not stable among populations. In some populations, not only sexual dimorphism in facial shape but also sex differences in skin color contribute to the overall facial dimorphism. Furthermore, it has been shown that skin color is an important trait associated with facial attractiveness in populations showing high variation in skin color, especially in Africans54,55. This means that facial dimorphism cannot be considered only by the facial shape, and there is still a place for sexual selection that may act upon non-shape-associated facial traits. Moreover, it seems that some color traits (such as iris color) are systematically associated with the sex-specific facial shape56,57. Future studies using information involving sex differences in these other attributes rather than shape should be considered. Finally, although the present study does not provide a convincing explanation about whether the sexual dimorphisms, which were determined in the present study to be unique to each population group, represent consequences of natural selection for population affinity that successfully adapted to dietary environments for many generations. Therefore, although we must be cautious about the limitations of interpreting these data, the results of the present study further enhance our understanding of human sexual dimorphism expressed in the oral and facial regions.

About 40% of students experienced depression and anxiety symptoms prior to entering/ during the transition to university: Role of Self-critical Perfectionism

Levine, Shelby L., Nassim Tabri, and Marina Milyavskaya. 2021. “Trajectories of Depression and Anxiety Symptoms over Time in the Transition to University: Their Co-occurrence and the Role of Self-critical Perfectionism.” PsyArXiv. May 27. doi:10.31234/osf.io/zxg8h

Abstract: Little is known about how mental health symptoms develop during the transition to university. Most anxiety and depression research fail to consider how symptom development differs over time across different individuals, and how symptom co-occurrence influences the severity of mental heath problems. Students (N = 658) completed online surveys on mental health prior to starting university and every 2 months until April. To better understand mental health problems during this transitional period, latent class growth curve analyses were run to determine how anxiety and depressive symptoms co-develop over time, as well, if self-critical perfectionism was a transdiagnostic risk factor for more severe symptom trajectories in this transition. About 40% of students experienced depression and anxiety symptoms prior to entering/ during the transition to university. There is substantial variation between students in terms of how they experience depression and anxiety symptoms, and research needs to take this heterogeneity into account to properly identify which students might benefit most from resources. Self-critical perfectionism was a transdiagnostic risk factor, such that students higher in this trait experienced more severe anxiety and depressive symptom trajectories during this transition. This research further implicates the importance of understanding and studying individual differences in symptom development.

Testosterone, T, was associated with more (less) advantaged socioeconomic position & better (worse) health among men (women), but previous associations of T & position may reflect influence of position on T

Testosterone and socioeconomic position: Mendelian randomization in 306,248 men and women in UK Biobank. Sean Harrison et al. Science Advances, 2021; 7 : eabf8257. July 28 2021. https://advances.sciencemag.org/content/advances/7/31/eabf8257.full.pdf

Abstract: Men with more advantaged socioeconomic position (SEP) have been observed to have higher levels of testosterone. It is unclear whether these associations arise because testosterone has a causal impact on SEP. In 306,248 participants of UK Biobank, we performed sex-stratified genome-wide association analysis to identify genetic variants associated with testosterone. Using the identified variants, we performed Mendelian randomization analysis of the influence of testosterone on socioeconomic position, including income, employment status, neighborhood-level deprivation, and educational qualifications; on health, including self-rated health and body mass index; and on risk-taking behavior. We found little evidence that testosterone affected socioeconomic position, health, or risk-taking. Our results therefore suggest that it is unlikely that testosterone meaningfully affects these outcomes in men or women. Differences between Mendelian randomization and multivariable-adjusted estimates suggest that previously reported associations with socioeconomic position and health may be due to residual confounding or reverse causation.

Rolf Degen summarizing... The brain circuit for pain is different from that for suffering, and the latter adds the bite to the former, and to other kinds of disorder

The anatomy of pain and suffering in the brain and its clinical implications. Dirk De Ridder, Divya Adhia, Sven Vanneste. Neuroscience & Biobehavioral Reviews, August 16 2021 https://doi.org/10.1016/j.neubiorev.2021.08.013

Highlights

• Acute pain is a symptom of acute or potential tissue damage, chronic pain extends beyond the period of healing of the original insult or injury, and hence lacks the acute warning function of physiological nociception.

• Pain can be anatomically and phenomenologically dissected into three separable but interacting pathways, a lateral ‘painfulness’ pathway, a medial ‘suffering’ pathway and a descending pain inhibitory pathway.

• In chronic pain the descending pain inhibitory pathway is less activated.

• Pain sensation leads to suffering via a cognitive (insula), emotional (ACC) and autonomic (ACC plus insula) processing, and is expressed as anger, fear, frustration, anxiety and depression, leading to changes in behaviour and functional disability.

• Acute pain transitions into chronic pain under influence of genetic and epigenetic factors.

• The genetic and epigenetic factors modulate neuroinflammation, which is involved in peripheral and central sensitization.

• Chronic pain, with a prevalence of 20-30% is the major cause of human suffering worldwide.

• Perceived pain disability correlates highly with suffering, little with painfulness

• Unpleasantness (and suffering) is transmitted via a phylogenetically old unmyelinated C-fibre network, linked to survival and procreation.

• Pain and suffering depend on salience and context: sadomasochistic erotic behaviour is a clear example.

• The medial pathway overlaps with the salience and stress networks, explaining that behavioural relevance or meaning determines the suffering associated with painfulness.

• Suffering explains the common neurocircuitry of many psychiatric and neurological disorders.

• Women perceive more intense acute and chronic pain and experience more unpleasantness than men.

• Women suffer more than men as evidenced by higher anxiety and depression prevalence.

• The sex-differences in pain perception are genetically encoded and dependent on immunological and hormonal modulation of pain processing.

• The (predictive) Bayesian Brain hypothesis proposes that pain (and suffering) is the consequence of an imbalance between the ascending and descending pain inhibitory pathways. This balance is theorized to be under control of the reward system.

• By categorizing the working mechanisms of each of the available treatments (pain killers, psychopharmacology, psychotherapy, neuromodulation, psychosurgery, spinal cord stimulation) to 1 or more of the 3 pathways, a rational combination can be proposed of activating the descending pain inhibitory pathways in combination with inhibition of the medial and lateral pathway, so as to rebalance the pain (and suffering) pathways.

Abstract: Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage. Chronic pain, with a prevalence of 20-30% is the major cause of human suffering worldwide, because effective, specific and safe therapies have yet to be developed. It is unevenly distributed among sexes, with women experiencing more pain and suffering. Chronic pain can be anatomically and phenomenologically dissected into three separable but interacting pathways, a lateral ‘painfulness’ pathway, a medial ‘suffering’ pathway and a descending pain inhibitory pathway. One may have pain(fullness) without suffering and suffering without pain(fullness). Pain sensation leads to suffering via a cognitive, emotional and autonomic processing, and is expressed as anger, fear, frustration, anxiety and depression. The medial pathway overlaps with the salience and stress networks, explaining that behavioural relevance or meaning determines the suffering associated with painfulness. Genetic and epigenetic influences trigger chronic neuroinflammatory changes which are involved in transitioning from acute to chronic pain. Based on the concept of the Bayesian brain, pain (and suffering) can be regarded as the consequence of an imbalance between the two ascending and the descending pain inhibitory pathways under control of the reward system. The therapeutic clinical implications of this simple pain model are obvious. After categorizing the working mechanisms of each of the available treatments (pain killers, psychopharmacology, psychotherapy, neuromodulation, psychosurgery, spinal cord stimulation) to 1 or more of the 3 pathways, a rational combination can be proposed of activating the descending pain inhibitory pathways in combination with inhibition of the medial and lateral pathway, so as to rebalance the pain (and suffering) pathways.

Keywords: painacutechroniccognitiveemotionalautonomicanterior cingulate cortex