Chimpanzees and humans establish preferences over individuals they may benefit more from through scoring indirect reputation; however, humans prefer prosocial individuals even at their own cost

Effects of indirect reputation and type of rearing on food choices in chimpanzees (Pan troglodytes). Nereida Bueno-Guerra, Montserrat Colell & Josep Call. Behavioral Ecology and Sociobiology volume 74, Article number: 79 (2020). Jun 6 2020. https://doi.org/10.1007/s00265-020-02861-w

Abstract: Chimpanzees and humans establish preferences over individuals they may benefit more from through scoring indirect reputation. However, humans prefer prosocial individuals even at their own cost. Giving preference to prosocial reputation over material rewards might have permitted the establishment of cooperative human societies. We tested the evolutionary roots of this propensity: importantly, in our study, the reputation scored had no food involved. Eighteen chimpanzees watched a performance where an antisocial experimenter hit a human victim and a prosocial experimenter interrupted the fight and consoled the victim. Next, the chimpanzees begged food from one of them. In Phase 2, the experimenters offered different food amounts (antisocial + 4 vs. prosocial + 1). Chimpanzees significantly prioritized rewards over reputation (i.e., chose antisocial). In Phase 3, both experimenters offered two pieces of food. Most of the subjects showed indifference to reputation (i.e., chose randomly). Watching fights produced significantly more arousal than consolations. Emotional engagement could not account for chimpanzees’ choices since their choices varied between phases but their arousal did not. Ontogeny and rearing history might play a role in chimpanzees’ choices: the adolescent males (n = 3) consistently chose the antisocial individual whereas hand-reared subjects chose significantly different from mother-reared. We discuss whether the valence of the reputation is species-specific.

Significance statement: From an evolutionary perspective, being able to learn indirect reputation is relevant for the individual’s fitness. Both chimpanzees and humans have previously proved to choose those who will presumably behave in the future in a way they could benefit from, suggesting similar underlying cognitive processes that would have emerged at an earlier common ancestor. However, both species approach differently to prosocial individuals. Humans live in societies where there is common agreement about certain universal rights which should always prevail, and thus they are more willing to approach prosocial individuals, even at their own cost. By contrast, in our study, chimpanzees, whose societies are based on unequitable distribution of power and resources, were not that willing to consistently and costly approach prosocial individuals. Moreover, other interpersonal factors, such as the type of upbringing or age-related changes in behavior (aggressiveness during adolescence), might have accounted for these differences.

Volitional Control of Individual Neurons in the Human Brain

Volitional Control of Individual Neurons in the Human Brain. Kramay Patel et al. bioRxiv, May 6 2020. https://doi.org/10.1101/2020.05.05.079038

Abstract: Can the human brain, a complex interconnected structure of over 80 billion neurons learn to control itself at the most elemental scale – a single neuron. We directly linked the firing rate of a single (direct) neuron to the position of a box on a screen, which participants tried to control. Remarkably, all subjects upregulated the firing rate of the direct neuron in memory structures of their brain. Learning was accompanied by improved performance over trials, simultaneous decorrelation of the direct neuron to local neurons, and direct neuron to beta frequency oscillation phase-locking. Such previously unexplored neuroprosthetic skill learning within memory related brain structures, and associated beta frequency phase-locking implicates the ventral striatum. Our demonstration that humans can volitionally control neuronal activity in mnemonic structures, may provide new ways of probing the function and plasticity of human memory without exogenous stimulation.

Firms whose names are lexicographically earlier in the Chinese-character rank export more to countries that have greater language proximities to Chinese; same for English-romanization names

Lexicographic biases in international trade. Hua Cheng, Cui Hu, Ben G. Li. Journal of International Economics, May 30 2020, 103346. https://doi.org/10.1016/j.jinteco.2020.103346

Highlights
• This study identifies a new type of bias in international trade patterns.
• We use an empirical strategy that exploits the interplay between firm-name lexicographic variations and destination-country language proximity variations.
• The Chinese language is outside the Indo-European system, a linguistic feature that strengthens our identification.
• Quantitative, lexicographic biases are approximately one to three percent of export volume.
• In a nutshell, Exporter A exports more than Exporter Z to countries that speak languages that are more proximate to English.

Abstract: The names of traders should not matter if information is symmetric across traders. By examining export data from Chinese customs, we find persistent lexicographic biases in firm-level export records. Firms whose names are lexicographically earlier in the Chinese-character rank export more to countries that have greater language proximities to Chinese, while firms whose names are lexicographically earlier in the English-romanization rank export more to countries that have greater language proximities to English. The lexicographic biases signify linguistic visibility as a source of comparative advantage in international trade.

Keywords: Alphabetic biasLanguageGravity modelsBehavioral economics

Individuals vulnerable to depression are less likely to identify with mainstream conservative parties, to vote for them, and to place themselves on the right side of the political spectrum

Depression and political predispositions: Almost blue? Luca Bernardi. Party Politics, June 9, 2020. https://doi.org/10.1177/1354068820930391

Abstract: This article explores the relationship between depression—one of the most common mental health problems in our societies—and political predispositions. Drawing on cross-disciplinary research from psychology, psychiatry, and political science, the article uses data from Understanding Society and the European Social Survey to test this relationship with party identification, vote intentions and left–right orientation, and two different measures of self-rated clinical depression and depressive symptoms. Empirical analyses find a modest but significant, common tendency: individuals vulnerable to depression are less likely to identify with mainstream conservative parties, to vote for them, and to place themselves on the right side of the political spectrum (a “bias against the right”). No clear evidence is found that they also identify less with political parties. These findings contribute to our understanding of differences in political predispositions and raise important implications for political engagement.

Keywords: depression, health, left–right, party identification, political predispositions

Personality and Sexual Orientation: New Data and Meta-analysis

Personality and Sexual Orientation: New Data and Meta-analysis. Mark S. Allen & Davina A. Robson. The Journal of Sex Research , Jun 8 2020. https://doi.org/10.1080/00224499.2020.1768204

ABSTRACT: This research explored associations between personality and sexual orientation. In Study 1, we explored whether the Big Five trait dimensions relate to sexual orientation in a nationally representative sample of Australian adults (n = 13,351). Personality differences were observed between those who identified as heterosexual (straight), bisexual, and homosexual (gay/lesbian) on all five measured traits. In Study 2, we conducted an updated systematic review and meta-analysis of personality and sexual orientation. A total of 21 studies (35 independent samples, 262 effect sizes) comprising 377,951 men and women were identified that satisfied inclusion criteria. Results showed that bisexual individuals reported higher levels of openness than homosexual individuals, who in turn, reported higher levels of openness than heterosexual individuals. Bisexual individuals also report lower levels of conscientiousness than both heterosexual and homosexual individuals. Sex moderation effects showed that homosexual men scored higher than heterosexual men on neuroticism, agreeableness and conscientiousness, whereas homosexual women scored lower than heterosexual women on extraversion, agreeableness, and conscientiousness. There was also evidence that personality differences between sexual orientation categories tend to decline with age. These findings align with the gender-shift hypothesis and should be of interest to theorists working in personality science and sexual identity development.

Discussion

Study 2 updated a recent meta-analysis of personality and sexual orientation (Allen & Walter, 2018a) to include bisexual orientation as a separate category. In contrast to the previous meta-analysis, that analyzed 110 effect sizes, the current meta-analysis extracted 262 effect sizes and computed separate analyzes for studies adopting self-reported sexual identity measures and non-convenience population-based samples. As in Study 1, notable differences were observed on all five trait dimensions between those who identified as heterosexual, those who identified as homosexual, and those who identified as bisexual. Study 2 also tested age moderation effects and found some evidence that personality trait differences between people of different sexual orientations tend to decline with age. Effect size differences for significant effects tended to be small-medium, and for non-significant effects the absence of a meaningful effect could not always be established using two-one-sided equivalence tests.

General Discussion

This research sought to determine whether personality differs between heterosexual, bisexual, and homosexual persons. Findings from Study 2 (that integrate Study 1) indicate that bisexual individuals report higher levels of openness than homosexual individuals, who in turn, report higher levels of openness than heterosexual individuals. Bisexual individuals also showed lower levels of conscientiousness than heterosexual and homosexual individuals. Sex moderation effects were observed for neuroticism, extraversion, agreeableness, and conscientiousness. These effects were such that homosexual men scored higher than heterosexual men on neuroticism, agreeableness and conscientiousness, whereas homosexual women scored lower than heterosexual women on extraversion, agreeableness, and conscientiousness. There was also evidence that personality trait differences between sexual orientation categories tend to decline with age. Overall, the findings of this research suggest small-medium effect size differences in trait personality between persons of different sexual orientation.

The finding that homosexual men and women scored higher on openness than heterosexual men and women is consistent with findings reported in a recent meta-analysis (Allen & Walter, 2018a) as well as theoretical propositions that openness should be most important for sexual identity formation (Lippa, 2005; Zoeterman & Wright, 2014). An important finding was that bisexual individuals reported higher levels of openness than both heterosexual individuals (medium effect size) and homosexual individuals (small effect size). This indicates that the association between openness and sexual orientation – if considered on a continuum from completely heterosexual to completely homosexual – is curvilinear in nature. This finding might be anticipated given that bisexual individuals tend to experience more identity confusion and emotional turmoil than homosexual individuals (Balsam & Mohr, 2007) meaning high levels of openness might be a useful attribute to discourage identity foreclosure (making a commitment without full exploration) among those who might otherwise adopt a bisexual orientation (see Zoeterman & Wright, 2014).

The findings of this research differ somewhat from those reported in a recent meta-analysis (Allen & Walter, 2018a) that found limited evidence for the gender-shift hypothesis. The previous meta-analyzes found that heterosexual and homosexual persons did not differ on extraversion, agreeableness or conscientiousness (Allen & Walter, 2018a). In fact, the only sex moderation effect observed was for neuroticism in which homosexual men reported higher levels of neuroticism than heterosexual men and homosexual women reported lower levels of neuroticism than heterosexual women. None of those findings were observed here. Rather, the neuroticism sex moderation effect indicated that while heterosexual men did score lower on neuroticism than homosexual (and bisexual) men, homosexual and heterosexual women did not differ in levels of neuroticism. Important sex moderations were also observed for extraversion (such that homosexual women report higher levels of extraversion than heterosexual women, but levels of extraversion did not differ between homosexual and heterosexual men), agreeableness (such that homosexual women report lower levels of agreeableness than heterosexual women, whereas homosexual men report higher levels of agreeableness than heterosexual men), and conscientiousness (such that homosexual women report lower levels of conscientiousness than heterosexual women, whereas homosexual men report higher levels of conscientiousness than heterosexual men).

By separating effects for bisexual and homosexual individuals, and focusing on higher quality studies (studies of self-reported sexual identity and representative data samples), we have been able to remove much of the excessive heterogeneity observed in the previous meta-analysis, narrowing confidence intervals, and revealing important sex moderations. That sex moderation effects were observed on four of the five dimensions provides some evidence for the gender-shift hypothesis (Lippa, 2005). Compared to men, women tend to score higher on neuroticism and agreeableness, and to a lesser extent, on extraversion and conscientiousness (De Bolle et al., 2015; Schmitt et al., 2008). Given these personality differences between men and women, the sex moderation effects observed for neuroticism, agreeableness and conscientiousness (between homosexual and heterosexual individuals) are in the direction predicted by the gender-shift hypothesis. The sex moderation effect for extraversion – showing that homosexual women score higher that heterosexual women on extraversion – is not in the direction predicted by the gender-shift hypothesis given that heterosexual women tend to score higher on extraversion than heterosexual men (albeit with a small effect size). This finding might be explained by cultural factors, as sex differences in extraversion do not always transfer across world regions (Schmitt et al., 2008).

Another important new finding was that bisexual individuals tend to score lower on conscientiousness than heterosexual and homosexual individuals, and this effect emerged for both men and women. Combined with the sex moderation effect for homosexual and heterosexual individuals (the finding that homosexual women report lower levels of conscientiousness than heterosexual women, whereas homosexual men report higher levels of conscientiousness than heterosexual men), this pattern of results is indicative of a curvilinear effect for conscientiousness (similar to openness) but only among women. For men, this pattern of results is indicative of a linear association (see Table 4). Because bisexual individuals tend to experience more identity confusion and emotional turmoil than homosexual individuals (Balsam & Mohr, 2007), we can speculate that – similar to high openness – low conscientiousness might be a useful attribute to discourage identity foreclosure (see Zoeterman & Wright, 2014) but only among women. For men, low conscientiousness might be less important to processes involved in identity formation and further research is required to help understand why this might be the case. Further research into these processes could also help to explain why a bisexual orientation is more common among women than among men (Bailey et al., 2016).

Researchers have invested a considerable amount of time investigating how trait personality changes over the lifespan (Caspi et al., 2005; Costa et al., 2019; Damian et al., 2019; Roberts et al., 2006). This research indicates that as people become older neuroticism tends to decrease, whereas agreeableness and conscientiousness tend to increase (the maturity principle). The age moderation effects observed in the current study – showing that differences between sexual orientation groups tend to decline with age – might be important to understanding personality trajectories. It was found that the medium effect size difference in neuroticism between heterosexual and homosexual men, the small effect size difference in extraversion between heterosexual and homosexual women, the small-medium effect size difference in openness between heterosexual, bisexual and homosexual women, and the small effect size difference in agreeableness between heterosexual and homosexual women, all decreased in magnitude as the sample age increased. Given these age moderation effects, sexual orientation might be an important consideration in personality trajectories across the lifespan. It might be the case that general personality trajectories (decreases in neuroticism, and increases in agreeableness and conscientiousness) differ in sexual minority samples. Compared to heterosexual men, homosexual men might show a greater decline in neuroticism and less of a decline in agreeableness and conscientiousness. Compared to heterosexual women, homosexual women might show a greater decline in agreeableness and conscientiousness. Longitudinal research is needed to test these possibilities directly.

The current research has a number of potential shortcomings that readers must consider when interpreting findings. First, while the current meta-analysis provides estimates for population-based samples, the samples included were somewhat limited to industrialized nations and how well findings transfer to all world regions remains unknown. Indeed, sex differences in personality do not always transfer across cultures (Schmitt et al., 2008) and further research in needed to test whether personality differences between people of different sexual orientations can be applied to all world regions. Second, the meta-analysis tested for linear effects between three sexual orientation categories. The pattern of results indicated that some associations might be curvilinear in nature if sexual orientation is considered on a continuum from fully heterosexual to fully homosexual. Researchers have suggested that in-between groups (e.g., primarily heterosexual, mostly homosexual) might also be important and distinct sexual minority categories (Savin-Williams, 2016; Walton et al., 2016) and future research might consider exploring (more directly) the magnitude of potential curvilinear effects. There is also some evidence that people who identify as asexual (no sexual attraction to persons of either sex) have distinct personality profiles (Bogaert et al., 2018; Carvalho et al., 2017) and further research into asexual samples is also important. In addition, other non-heterosexual identity labels are increasingly being used (e.g., pansexual, queer; Goldberg et al., 2020) that could also be explored in relation to personality.

A third limitation is the focus on higher-level personality dimensions rather than lower-level trait facets. Research has found that women tend to score higher than men on extraversion facets related to warmth and sociability, whereas men tend to score higher than women on extraversion facets related to assertiveness and excitement seeking (Costa et al., 2001). To more adequately test the gender shift hypothesis, researchers should look to explore lower-level trait facets. A fourth potential limitation relates to measurement differences in sexual orientation with some studies focusing on self-reported sexual identity (categorized) and others exploring relative levels of same-sex sexual attraction. These differences in conceptualization might contribute somewhat to increased measurement error. A final limitation is that included studies used cross-sectional research designs and therefore whether associations between personality and sexual orientation are spurious or causal in nature remains unknown. Prospective research designs can help provide information on how personality development and sexual identity development interconnect over the adult lifespan.

Despite these potential limitations, the current research extends knowledge in this important area and findings for all five personality dimensions reported in the previous meta-analysis (Allen & Walter, 2018a) have been superseded in this work. For neuroticism, our results show that rather than sexual orientation differences for both men and women (Allen & Walter, 2018a), only men tend to differ on scores for neuroticism. For openness, rather than a straightforward difference between heterosexual and homosexual persons (Allen & Walter, 2018a), our results indicate a curvilinear association in which bisexual individuals score highest on openness. For extraversion, agreeableness and conscientiousness, rather than no personality differences across sexual orientation categories for men or women (Allen & Walter, 2018a), our results show sex moderation effects in which sexual orientation groups differ on all these dimensions. Furthermore, rather than these differences being static across the lifespan (i.e., no age moderation effects; Allen & Walter, 2018a), our results indicate that personality differences between persons of different sexual orientation tend to decline with age. In other words, the current research provides more precise estimates in meta-analysis and greater support for the gender-shift hypothesis overall.

In terms of research progression, researchers might consider exploring further how personality relates to processes important in sexual identity formation. The minority stress model of sexual orientation (Meyer, 2003) outlines that sexual minorities are at greater risk of mental health problems (see Allen, 2018; Semlyen et al., 2016), because of stigma, prejudice, and discrimination that create a stressful social environment. The degree to which sexual minority individuals are susceptible to such stress is thought to be moderated by personality traits (Bailey, 2020) that are particularly important in stress and coping (Carver & Connor-Smith, 2010; Connor-Smith & Flachsbart, 2007). Researchers might also consider exploring further how personality relates to stages of sexual identity development. Stage based models (e.g., Cass, 1979) have received some criticism for not considering individual difference factors that might explain why some individuals do not progress through stages in a linear manner or progress through all stages (Rosario et al., 2011). These variations in identity formation might be explained, in part, by personality traits and further research into these processes can help increase understanding of sexual identity development.

To conclude, this research has identified small-medium effect size differences in personality traits between heterosexual, bisexual, and homosexual persons. Important differences were found on all five personality dimensions, and effects were generally in line with predictions of the gender-shift hypothesis. Results also showed that personality trait differences between sexual orientation categories tend to decline with age. The findings of this research could have implications for theory and research on personality trajectories over the lifespan, and might also be of interest to health care professionals working with sexual minority (LGB) individuals. Sexual identity development can be a complex and often difficult process (Rosario et al., 2011) and personality tests might become a useful method to identify individuals who might benefit greatest from inclusion in support programs for sexual identity distress. More generally, personality tests could be useful in helping LGB individuals gain greater self-awareness of their own personality. We recommend further research using prospective designs, in understudied cultural groups and world-regions, and more rigorous tests of potential curvilinear associations, to further understand how personality and sexual orientation interconnect over the lifespan.

Large double-blind & placebo-controlled replication of an influential paper, Kosfeld et al. 2005 (intranasal administration of oxytocin increases the transfers made by investors in the trust game), fails

A registered replication study on oxytocin and trust. Carolyn H. Declerck, Christophe Boone, Loren Pauwels, Bodo Vogt & Ernst Fehr. Nature Human Behaviour, Jun 8 2020. https://www.nature.com/articles/s41562-020-0878-x

Abstract: In an influential paper, Kosfeld et al. (2005) showed that intranasal administration of oxytocin (OT) increases the transfers made by investors in the trust game—suggesting that OT increases trust in strangers. Subsequent studies investigating the role of OT in the trust game found inconclusive effects on the trusting behaviour of investors but these studies deviated from the Kosfeld et al. study in an important way—they did not implement minimal social contact (MSC) between the investors and the trustees in the trust game. Here, we performed a large double-blind and placebo-controlled replication study of the effects of OT on trusting behaviour that yields a power of more than 95% and implements an MSC condition as well as a no-social-contact (NoC) condition. We find no effect of OT on trusting behaviour in the MSC condition. Exploratory post hoc analyses suggest that OT may increase trust in individuals with a low disposition to trust in the NoC condition, but this finding requires confirmation in future research.

The Hadza report a higher happiness with their lives than do Polish people; age was a negative predictor of happiness only for Poles; maybe a positive perception of aging in societies may increase happiness

Subjective Happiness Among Polish and Hadza People. Tomasz Frackowiak, Anna Oleszkiewicz, Marina Butovskaya, Agata Groyecka, Maciej Karwowski, Marta Kowal and Piotr Sorokowski. Front. Psychol., June 9 2020, https://doi.org/10.3389/fpsyg.2020.01173

Abstract: Life satisfaction and happiness were broadly studied in Western populations, whereas evidence from traditional societies remains surprisingly scarce. We collected data on the happiness from 145 Hadza, and compared it with data obtained from 156 Poles, representing Westernized society. Participants were asked to answer four simple questions from Subjective Happiness Scale (Lyubomirsky and Lepper, 1999). Results indicate that Hadza report a higher level of happiness with their lives than do Polish people. Our findings also show that sex was not related to happiness in both populations, while age was a negative predictor of happiness, but only among Poles. Therefore, we hypothesize that positive perception of aging in societies may increase their actual happiness.

Discussion

The current investigation aimed to explore happiness of Hadza hunter-gatherers and Poles. Results of both studies showed that Hadza reported a higher level of happiness with their lives compared with Polish people. In both studies, sex was not related to participants’ happiness. Exploratory analysis from the first study provided evidence for a curvilinear link between age and happiness among Poles (but not among Hadza). We have then confirmed this hypothesis in the second study, using a validated measurement – Subjective Happiness Scale. Age was a negative predictor of happiness in Poland, whereas no such relationship was observed in Hadza. Therefore, we hypothesize that positive perception of aging in societies may increase their actual happiness (Levy et al., 2002, 2014; Ingrand et al., 2018).

Albeit simpler and more nature-dependent life, highly egalitarian social structure, and a high degree of cooperation Hadza are known for Marlowe (2004, 2009), Apicella et al. (2012), Henrich (2012), can be named among possible reasons to explain the current findings in differences in happiness. Such social organization in Hadza might explain why the level of subjective happiness is independent from age, as opposed to Polish society, wherein subjective happiness declines with age. Perhaps Hadza of old age find their place in the social organization, and their contribution to the society remains high despite not being as fit as in younger age. The best illustration are Hadza grandmothers, investing actively in grandchildren, and providing better chances for their survival (Hawkes et al., 1997; Crittenden and Marlowe, 2008, 2013). Nevertheless, what is worth highlighting is that also numerous other factors can account for the observed differences between Hadza and members of the Western countries, for instance, differences in pollution, access to firearms, or living in communities of millions instead of 20–30 people (Welsch, 2006; Lankford, 2016; Okulicz-Kozaryn and Mazelis, 2018). Moreover, our results are contradictory to findings of previous studies, which suggested that the relationship between age and happiness in more developed, Western societies is U-shaped, with older people showing greater happiness than middle-aged (Blanchflower and Oswald, 2008; Wolpert, 2010). On the other hand, Frijters and Beatton (2012) provided evidence that the widely reported U-shape is just an artifact of the bias of coefficients of variables, which peak in middle-age (e.g., income, marriage, and employment).

Our results are intriguing in the light of previous findings on the material resources being a necessary condition for raising the level of happiness in the population (Devoto et al., 2012; Mahasuweerachai and Pangjai, 2018). Hadza present very remote and mobile way of living. Individuals change camps every few months and the whole population resides where natural resources (e.g., game, plants) allow their subsistence (Woodburn, 2017a, b). The lack of accumulated goods further eases mobility. We speculate that the relatively high level of Hadza happiness is rooted in their social organization and culture directed toward the community. In fact, happiness is related with communal, interpersonally-oriented traits and high positive affect (Furr, 2005). Moreover, many studies highlight the role of social support and social ties in developing and maintaining high levels of happiness and well-being (Chan and Lee, 2006; Aknin et al., 2011). It is, thus, not surprising that positive psychologists, psychotherapists, and even World Bank recommend fostering quality social ties, as they have a significant and positive effect on happiness (World Development Report, 2003; Lakey, 2013; Compton and Hoffman, 2019). Although evidence for the relationship between the social support, communion and happiness comes from the modern societies (Hermans, 1992; Helgeson, 1994), we speculate that communal behaviors are present and promoted among Hadza to a larger extent, as they manifests in hunting, sharing food and motherhood challenges (Hawkes et al., 1989, 2001; Marlowe, 2009; Apicella et al., 2012; Henrich, 2012), which can translate into a high level of happiness.

In the present research, we have used two measures of happiness – in the first study, we assessed happiness by referring to an affective aspect, whereas in the second study, we used Subjective Happiness Scale, which relates both to the affective and cognitive components (Lyubomirsky and Lepper, 1999). This may be important, as there are various definitions of happiness, including ones based entirely on emotions, and others based purely on thinking (Veenhoven, 2009). Findings of the present study suggest that both cognitively and affectively perceived happiness is higher among Hadza in comparison with more industrialized societies.

It would be interesting to test whether hunter-gatherer societies have higher happiness than pastoralists and agriculturalists. Agriculture opens the possibility for social stratification and exploitation. That is why some authors suggested that from the viewpoint of individual happiness, the “agricultural revolution” was the worst mistake in the history of the human race (see Harari, 2014). Such hypothesis could be explored in Hadza, whose territories are surrounded by Datoga pastoralists, and Iraqw agro-pastoralists. Moreover, as happiness can be affected by numerous factors (e.g., standard of living, or relationships), future studies should focus on exploring possible moderators of happiness in more traditional populations.

The readers may wonder whether the Hadza fully comprehended the given task (i.e., rating their happiness level). The authors have years of experience in conducting such studies, especially among the Hadza population, thus, with fairly high certainty, we can ensure that our participants understood the scales used in the present study. When the Hadza do not understand the question they are being asked, not only their facial expressions and non-verbal behavior change, but they also admit they do not comprehend the given task. Usually, when we have concerns about the question comprehension, we randomly ask the same questions twice. As we had no doubts that the Hadza understood the task of the present study, we did not perform such checking techniques. Nevertheless, this can be regarded as a potential limitation of the present study (and in general, many other studies conducted among the traditional, illiterate populations).

Another possible limitation of the present findings is that, due to the small samples, recruiting techniques, and lack of extensive information regarding participants from both populations, final samples do not necessarily represent well the whole societies they derive from (i.e., Polish and Hadza). Similarly, we chose Hadza and Poles as representatives of traditional and modern societies, having no certainty that Poles are indeed typical for all non-Western countries and Hadza do not necessarily represent all hunter-gatherer cultures. Nevertheless, Poles do present a modern, industrialized way of living and as members of European Union are strongly bonded with and influenced by other cultures of the West. Yet, one needs to bear these in mind when interpreting the results of the present study.

We would also like to note the fact that some of our statistical decisions may be considered suboptimal. In the first study we merged two categories of answers, namely “sad” and “sometimes happy and sometimes sad” into one category. We acknowledge that this decision might be considered problematic, but because we were interested in “happiness,” it made sense to dichotomize our participants into those who considered themselves “happy” vs. the rest. In the second study, we did not test for invariance in each group (i.e., Poles and Hadza) separately. Instead, we tested configural, metric and scalar invariance in multi-group CFA: a solution that resulted in higher statistical power of our analyses.

Disgust: While avoiding contaminated food is a key adaptive problem, we also had to avoid having sex with individuals that could harm our survival, our children’s survival, or generally reproductive success

Sexual Disgust: An Evolutionary Perspective. Courtney L. Crosby and David M. Buss.  Emotion Researcher, 2020. emotionresearcher.com/sexual-disgust-an-evolutionary-perspective/

Introduction: One of the first emotions explored by Charles Darwin, disgust, presumably evolved to solve adaptive problems related to our health. Examples of these problems include avoiding ingesting toxic or pathogenic substances, such as rotting meat or moldy mushrooms. However, a key scientific question is whether disgust evolved to solve adaptive challenges in addition to food consumption. Darwin described disgust as a revulsion to offensive objects, primarily those of taste, but extended to anything that causes extreme dislike or distaste—through vision, smell, or touch (Darwin, 1872). While avoiding contaminated food is a key adaptive problem that our human ancestors faced, they also had to avoid having sex with individuals that could harm their survival, their children’s survival, or more generally their reproductive success. Sexual disgust may have evolved as a somewhat specialized emotion—based on the underlying architecture of disgust—to solve these problems (Tybur, Lieberman, & Griskevicius, 2009).