Online perspective-taking experiments have demonstrated great potential in reducing prejudice towards disadvantaged groups, but had no meaningful causal effect on social welfare attitudes

Bor, Alexander, and Gábor Simonovits. 2020. “Empathy, Deservingness, and Preferences for Welfare Assistance: A Large-scale Online Perspective-taking Experiment.” PsyArXiv. January 29. doi:10.31234/osf.io/d4sm9

Abstract: Online perspective-taking experiments have demonstrated great potential in reducing prejudice towards disadvantaged groups such as refugees or the Roma. These studies trigger the psychological process of empathy and evoke feelings of compassion. Meanwhile, a growing literature argues that compassion towards the poor is an important predictor of support for social welfare. This paper bridges these two literatures and predicts that perspective-taking with the poor could increase support for welfare assistance. This hypothesis is tested with a pre-registered experiment conducted on a large and diverse online sample of US citizens (N=3,431). Our results suggest that participants engaged with the perspective-taking exercise, wrote eloquent, often emotional essays. Nevertheless, perspective-taking had no meaningful causal effect on social welfare attitudes; we can confidently rule out effects exceeding 2 points on a 100 points scale. These results cast serious doubt on perspective-taking as a viable online tool to create compassion towards the poor.


Discussion

In this paper, we have tested whether perspective-taking is a viable tool for increasing support for welfare redistribution. Relying on an original, carefully designed, well-powered, and pre-registered survey experiment elded to a representative sample of US citizens, we found that it is not. Similarly to successful interventions, we tested the impact of a particular stimulus, describing the experiences of a single target and emphasizing a particular set of challenges that poor people in the US face (unemployment, health problems, housing problems, single parenthood).
Thus, our conclusions about the possible e ectiveness of perspective-taking intervention are necessarily limited: We have no way of knowing if large or even small changes in the stimulus used here could have led to a more e ective intervention.
This leads to the question of the extent to which these null ndings advance our understanding of either the class of interventions or the substantive target attitude that we study.
This issue should be understood in the broader context of how the published experimental literature characterizes the e ect of a di erent class of interventions. There is ample evidence that published research over-represents successful interventions compared to the universe of social science experiments (Franco, Malhotra and Simonovits 2014; 2016). For a more complete understanding of how a given class of interventions – such as perspective-taking – works, one also needs to consider unsuccessful examples.
That said, it is also important to emphasize why we think that our null results are surprising. First, our experimental design relied on a heavy dose of deservingness cues, which, according to previous research, has a large and sometimes long-lasting e ect on support for redistribution. We expected the perspective taking exercise to amplify the e ects of these deservingness cues but found that it nulliffed it.
Second, our findings are surprising considering a growing line of research employing perspective taking to reduce prejudice against various groups from refugees to transgender individuals.
Our results suggest that prejudice against the poor and attitudes towards government help for the poor may be more di cult to shape than attitudes towards these other marginalized groups.
Third, our experimental design likely constitutes a liberal test of our hypothesis. Besides relying heavily on deservingness cues, we measure the dependent variable with a composite index of ten items after a distractor task lasting a few minutes. For this reason, the experiment should be able to pick up even small, fleeting effects. Finally, it is noteworthy that the analysis of the essays reveals that participants have been very attentive and engaged in the exercise. We have no reason to believe that if we had conducted our experiment in the lab, we would see different results.
At the same time, the literature also o ers some explanations for our failure to bring about attitude change using our perspective-taking intervention. On the one hand, our treatment might have proven too weak in the sense that even though subjects felt empathy towards the individual depicted in the vignette, these emotions did not spill over to people in need in general, perhaps because subjects viewed the vignette as an \exception" to some deeply held stereotypes about poor people.
On the other hand, intense exposure to a story about a person in need might have led to emotional reactions moving counter to our hypothesized e ect. For instance, as argued by Sands (2017) exposure to poverty might have provoked anxiety in subjects about their own relative status, suppressing their support for policies helping others. Similarly, as pointed out by Simas, Clifford and Kirkland (2020), heightened empathy might exacerbate in-group bias, leading to hostile attitudes towards members of an out-group.

What We Owe to Family: Agents who helped a stranger were judged as more morally good & trustworthy than those who helped kin, but agents who helped a stranger instead of kin were judged as less morally good & trustworthy

What We Owe to Family: The Impact of Special Obligations on Moral Judgment. Ryan M. McManus, Max Kleiman-Weiner, Liane Young. Psychological Science, January 28, 2020. https://doi.org/10.1177/0956797619900321

Abstract: Although people often recognize the moral value of impartial behavior (i.e., not favoring specific individuals), it is unclear when, if ever, people recognize the moral value of partiality. The current studies investigated whether information about special obligations to specific individuals, particularly kin, is integrated into moral judgments. In Studies 1 and 2, agents who helped a stranger were judged as more morally good and trustworthy than those who helped kin, but agents who helped a stranger, instead of kin were judged as less morally good and trustworthy than those who did the opposite. In Studies 3 and 4, agents who simply neglected a stranger were judged as less morally bad and untrustworthy than those who neglected kin. Study 4 also demonstrated that the violation (vs. fulfillment) of perceived obligations underlaid all judgment patterns. Study 5 demonstrated boundary conditions: When occupying roles requiring impartiality, agents who helped a stranger instead of kin were judged as more morally good and trustworthy than agents who did the opposite. These findings illuminate the importance of obligations in structuring moral judgment.

Keywords: morality, obligation, prosocial behavior, impartiality, open data, open materials, preregistered

Male bowerbirds add berries to their bowers to increase attractiveness to choosy mates; when berries are added artificially, increased intrasexual aggression in the form of bower destructions by neighbouring rivals occur

From 2002... Bower decorations attract females but provoke other male spotted bowerbirds: bower owners resolve this trade-off. Joah Robert Madden. Proceedings of the Royal Society B, Volume 269, Issue 1498, July 7 2002. https://doi.org/10.1098/rspb.2002.1988

Abstract: Elaborate secondary sexual traits offset the costs that they impose on their bearer by facilitating reproductive benefits, through increased success in intrasexual contests or increased attractiveness to choosy mates. Some traits enhance both strategies. Conversely, I show that spotted bowerbirds Chlamydera maculata may face a trade–off. The trait that best predicts their mating success, numbers of Solanum berries exhibited on a bower, also provokes increased intrasexual aggression in the form of bower destructions by neighbouring bower owners, which reduce the quality of the male's bower. At natural berry numbers, levels of mating success in the population are skewed, but levels of destruction do not vary with berry number. When berry numbers are artificially exaggerated, increased levels of destructions occur, but mating success does not increase. When offered excess berries, either to add to the bower or artificially placed on the bower, bower owners preferred to use numbers of berries related to the number that they displayed naturally. This decision is made without direct experience of the attendant changes in destruction or mating success. This indicates that bower owners may assess their own social standing in relation to their neighbours and modulate their display accordingly.

Germ theory, long before it led to medical treatments, drove down mortality rates by revolutionizing sanitation and hygiene

Draining the swamp. Jason Crawford. The Roots of Progress, Jan 28. https://rootsofprogress.org/draining-the-swamp

Excerpts (the original link has references & lots of charts... interesting throughout):

And the surprising thing I found is that infectious disease mortality rates have been declining steadily since long before vaccines or antibiotics.

I was surprised to learn that sanitation efforts began as early as the 1700s—and that these efforts were based on data collection and analysis, long before a full scientific theory of infection had been worked out. James Riley, in “Insects and the European Mortality Decline”, writes:3

In the later decades of the seventeenth and early decades of the eighteenth century, a number of internationally renowned physicians … formulated specific measures of intervention. Relying on Hippocratic tradition, specifically, on its suggestion that endemic and epidemic diseases are caused by forces in the environment, and influenced by Renaissance efforts at urban sanitation, these physicians proposed to discover the meteorological and topographical forces that might be blamed for the onset of epidemics. Toward this end, they and their followers embarked on a vast campaign to assemble qualitative and quantitative data about epidemics, climate and weather, geographical and topographical signs, and other features of the habitat. Their aim was to find conjunctures or correlations in the data, occasions when epidemics occurred after the same complex of environmental forces. Early signs of such a complex would offer warnings and allow the adoption of measures of prevention and avoidance. This body of medical theory failed to produce a coherent list of correlations, but it did provide a specific body of measures of avoidance and prevention.

In particular, they proposed (each bullet quoted from the article):

. to drain swamps, bogs, moats, and other sites of standing water
. to introduce hydraulic devices that would circulate water in canals and cisterns
. to flush refuse from areas of human habitation
. to ventilate living quarters and meeting places and to burn sulfur sticks or apply other insecticidal measures in houses, hospitals, prisons, meeting halls, and ships
. to inter corpses outside the city
. and by other measures, including refuse burial, to detach humankind from organic waste

These reforms were implemented starting in the 1740s, some by local and central governments, others by “humanitarians acting on private initiative”.

What broad changes were actually implemented, and is it plausible that they had a significant impact?

To have had a significant effect on insect numbers, the measures proposed by the environmentalists [the physicians advocating environmental cleanup] would have had to have been broadly applied across western Europe. Two measures, lavation and drainage, are particularly important in insect control, and we can focus on examples of their application. Lavation combines programs taking three forms: flushing filth from urban sites, collecting and disposing of refuse, and introducing devices to agitate or circulate standing water. By these means, which would cleanse streets, industrial sites, and buildings, and transform standing water in canals and cisterns into moving water, the environmentalists argued, the city might be made as healthy as the countryside. One model for these proposals was the naturally washed site of the town of Chester, England, where rain periodically flushed refuse into a subterranean drainage network cleansed by tidal action. The objective of the environmentalists was to introduce the same action by hydraulic engineering. Another model was the program followed in Hamburg to collect and dispose of refuse outside the city each day. A third was the improvement of streets by paving and widening, and of urban drainage networks by constructing or expanding sewage systems. Measures of one or another variety were adopted in many British cities and towns in the Improvement Acts of the 1760s and thereafter, and observers, such as William White in York, attributed declines in mortality specifically to them. In Paris, the drainage system was improved in 1740, and later in the century, other measures, including the emptying of cesspits and the installation of sewers, followed. In the Austrian Empire, Johann Peter Frank directed a broad campaign of medical policing, which included projects for refuse collection and disposal.

These efforts affected not only diseases such as malaria, where insects are the primary vector of infection, but also others such as dysentery in which insects (especially flies and cockroaches) can distribute the disease throughout the environment, e.g., from waste to food. Pest control thus provides the best explanation I’ve found for reductions in the mortality rate from the mid-1700s to early 1800s.

Cutler & Miller estimate10 that

the introduction of water filtration and chlorination systems led to major reductions in mortality, explaining nearly half of the overall reduction in mortality between 1900 and 1936. Our results also suggest that clean water was responsible for three-quarters of the decline in infant mortality and nearly two-thirds of the decline in child mortality. The magnitude of these effects is striking. Clean water also appears to have led to the near eradication of typhoid fever, a waterborne scourge of the 19th and early 20th Centuries.

Finally, the germ theory led to public health efforts to educate the populace on good general hygiene. A policy brief by Samuel Preston says:9

Enlightened public health officials were quick to recognize how the germ theory should guide their practice. Furthermore, by the time of the first White House Conference on Infant Mortality, held in 1909, they realized that rapid advances in longevity required that public officials go beyond their normal domain of public works and attempt to change the personal health practices of individuals. The germ theory provided a number of powerful weapons for doing so. These included boiling bottles and milk, washing hands, protecting food from flies, isolating sick children, and ventilating rooms. Public health officials launched massive campaigns to encourage these practices. In New York City, milk depots were established with the ostensible purpose of distributing milk to indigent mothers but with the real purpose, according to the director, of instructing mothers in hygienic practices. The New York City Department of Health produced one of the nation’s first motion pictures, entitled The Fly Pest. At the national level, the new Children’s Bureau adopted a primary focus on child health. Its pamphlet called Infant Care became the largest selling volume in the history of the Government Printing Office, with some 12 million copies sold by 1940. By the 1920s, the bureau was receiving and answering over 100,000 letters a year from parents seeking child care advice.

Thus the germ theory, long before it led to medical treatments, drove down mortality rates by revolutionizing sanitation and hygiene.

How many electric vehicles can the current Australian electricity grid support? Current grid can support EVs at 5–10% penetration under uncontrolled charging

How many electric vehicles can the current Australian electricity grid support?, Li and Lenzen, International Journal of Electrical Power & Energy Systems, Volume 117, May 2020. https://doi.org/10.1016/j.ijepes.2019.105586

Highlights
•    Hourly spatio-temporal electricity dispatch is modelled to meet EV load in Australia.
•    EV charging is spatially and temporally optimised using high-resolution GIS data.
•    Current grid can support EVs at 5–10% penetration under uncontrolled charging.
•    Controlled charging increases the ability to accommodate EVs to 60–70% penetration.
•    Controlled charging reduces electricity cost by up to around 4–6%.

Abstract: We quantitatively investigate the impact of uncontrolled and controlled charging demand of battery electric vehicles (BEVs) on electricity generation, loss-of-load probability (LOLP), and levelized cost of electricity (LCOE) in Australia. We consider both high- and low-fuel-economy (HE and LE) BEVs, assume BEV penetration rates (EVPR) ranging from 0 to 100%, and three controlled charging participation rates (0%, 53% and 100%). The spatio-temporal distribution of BEV load is estimated by a GIS-based probabilistic model at a high-resolution level for Australia. The BEV charging impact is simulated by an hourly supply-demand model, respecting currently existing installed capacity, operating technologies and LOLP standards, to simulate an electricity dispatch for an entire year. BEV charging is spatially and temporally optimised to achieve minimum levelized cost. We show that the current Australian national grid can support HE and LE BEVs at 5–10% penetration for uncontrolled charging, and around 60–70% for controlled charging. Controlled charging also reduces electricity cost by up to around 4–6%.

Keywords: Vehicle grid integration, Electricity generation simulation, GIS, Controlled charging

Immersive virtual reality: Het. men rated the female avatar’s touch as more appropriate & erogenous, while het. women rated female & male touches as equally appropriate (the latter being most erogenous)

Fusaro, Martina, Matteo Lisi, Gaetano Tieri, and Salvatore M. Aglioti. 2020. “Touched by Vision: How Heterosexual, Gay, and Lesbian People React to the View of Their Avatar Being Caressed on Taboo Body Parts.” PsyArXiv. January 28. doi:10.31234/osf.io/dkzj5

Abstract: Embodying an artificial agent through immersive virtual reality (IVR) may lead to feeling somatosensory stimuli on one’s body which are in fact never delivered. What remains unknown is whether the vicarious touch in virtual reality reflects the basic individual and social features of real-life interpersonal interactions. Here, we explored the subjective and objective reactivity of heterosexual men/women (Study 1) and of gay men/lesbian women (Study 2) to the observation of a gender-matched virtual body being touched on different body parts, including the breast and genitalia, by male and female avatars. In addition to the illusory feeling of being touched and of owning the virtual body, participants reported on different aspects of the experience (e.g., appropriateness, erogeneity). Physiological measures of autonomic reactivity were also collected. Heterosexual men rated the female avatar’s touch as more appropriate and erogenous, while heterosexual women rated female and male avatar touches as equally appropriate, with the latter being most erogenous. Interestingly, gay men exhibited the same pattern of appropriateness and erogeneity as heterosexual women. In contrast, lesbian women rated more appropriate and erogenous the touches of the female avatar. For all participants, the most appropriate and erogenous regions were the social and the intimate ones, respectively. Importantly, touches on the virtual body’s intimate areas elicited the highest skin conductance response when participants were touched by a female avatar. Thus, IVR may easily induce vicarious experiences and ultimately allow the direct exploration of sensitive societal and individual issues that can otherwise be explored only through imagination.

From 2018... The First Ejaculation: A Male Pubertal Milestone Comparable to Menarche?

From 2018... The First Ejaculation: A Male Pubertal Milestone Comparable to Menarche? Jordan A. Chad. The Journal of Sex Research, Volume 57, 2020 - Issue 2, Pages 213-221, Nov 30 2018. https://doi.org/10.1080/00224499.2018.1543643

Abstract: Boys experience their first ejaculation (thorarche) during adolescence, but this event is often overlooked as a milestone in male adolescent development. The purpose of this article is to draw attention to thorarche and consider it in comparison with the female milestone of menarche. A critical analysis is provided of how thorarche has been interpreted to date and the complexities in construing thorarche from a biological perspective are outlined. Despite potential tenability of characterizing thorarche as a comparable milestone to menarche, two particular points challenge this notion: (a) While thorarche may befall the boy involuntarily, it may also be induced by the boy’s own will; and (b) Thorarche occurs concomitantly with (pubertal) orgasmarche and has an innate connection with sexuality. The answer to the title question remains contentious, but open topics for future research are noted throughout the article as essential steps towards attaining a better understanding of thorarche.

Hormonal contraceptive use and subjective sleep reports in women: An online survey

Hormonal contraceptive use and subjective sleep reports in women: An online survey. Andréia Gomes Bezerra  Monica Levy Andersen  Gabriel Natan Pires  Carolina V. Banzoli  Daniel Ninelo Polesel  Sergio Tufik  Helena Hachul. Journal of Sleep Research, January 27 2020 https://doi.org/10.1111/jsr.12983

Abstract: Female sexual hormones have known hypnogenic effects and the use of hormonal replacement therapy in postmenopausal women leads to improvement in sleep quality. However, the effects of hormonal contraceptives in women of reproductive age are still scarcely understood. This study sought to evaluate the impact of hormonal contraceptive use on subjective self‐reports of sleep through a web‐based cross‐sectional survey. A total of 2,055 women between 18 and 40 years old participated by answering an online questionnaire evaluating hormonal contraceptive use, sleep‐related characteristics and related features. Sleep assessment tools comprised the Epworth Sleepiness Scale (ESS) and the Insomnia Severity Index (ISI). Statistical comparisons were performed between hormonal contraceptive users and those who reported no current use. Analyses were repeated to compare users of combined contraceptives with users of progestagens only, as well as to compare users of different generations of contraceptives. Among the total sample, 1,286 participants met the inclusion criteria (918 of them were currently taking a hormonal contraceptive). Contraceptive users reported more frequent sleep complaints and had higher scores on ESS and ISI, which means increased excessive daytime sleepiness and more insomnia symptoms. Women using progestagen‐only therapies reported lower total sleep duration compared with combined therapy. Users of third‐generation contraceptives showed lower total sleep time and higher ISI score when compared with non‐users. In conclusion, contraceptive users have more insomnia symptoms and increased excessive daytime sleepiness when compared with women who do not use any hormonal contraceptive method, and progestagen‐only therapy was associated with lower sleep duration.

Individual & Joint Pornography Use Among Romantic Couples: Partner knowledge of use had little direct association with well-being, but unknown individual use may be associated with less sexual, but more relationship, satisfaction

Behind Closed Doors: Individual and Joint Pornography Use Among Romantic Couples. Brian J. Willoughby & Nathan D. Leonhardt. The Journal of Sex Research, Volume 57, 2020 - Issue 1, Pages 77-91. https://doi.org/10.1080/00224499.2018.1541440

Abstract: Most previous research on the associations between pornography use and relational well-being has utilized individual data sets that have limited scholars’ ability to truly understand the dyadic nature of pornography use within romantic couples. Using a dyadic data set of 240 committed heterosexual couples from the United States, we explored actor and partner associations between pornography use, sexual dynamics, and relational well-being. We also explored how couple pornography use and partner knowledge of pornography use were associated with well-being. Results suggested that female pornography use was associated with higher female sexual desire but no other dependent variables. Male pornography use was associated with a wide array of negative well-being indicators, including less male and female relationship satisfaction, lower female sexual desire, and lower male positive communication. Couple pornography use was associated with higher reported sexual satisfaction for both partners but no other well-being indicators. Partner knowledge of use had little direct association with well-being, but some evidence suggested that unknown individual use may be associated with less sexual satisfaction but more relationship satisfaction. Results suggest that different configurations of use among heterosexual couples are associated with varying relational well-being indicators.

Norway: The higher risk of childlessness was associated with the highest intelligence score, & and this effect was mediated by whether participants had ever been in a relationship by their late twenties

Does Intelligence Predict Childlessness in Men? An Analysis of the Direct and Indirect Associations Between Intelligence and Childlessness in Men. Audun Hustad Torgersen. Oslo University, Oct 15 3019. https://www.duo.uio.no/bitstream/handle/10852/72403/1/Does-Intelligence-Predict-Childlessness-In-Men.pdf

Background: In many European countries, the rate of childlessness has increased and this increase is disproportionately large among men. It is thus important to study the antecedents of childlessness. Intelligence as a predictor of childlessness has received some attention, although the findings are conflicted. Men with less education, lower wages and no partner seem to be overrepresented among the childless. These factors are known to be associated with intelligence. However, little is known about how these factors may mediate the association between intelligence and childlessness.

Method: The present study analyzed data from the Young in Norway survey, which had been linked to the Historical Event Database (FD-Trygd) of Statistics Norway, in addition to intelligence scores from the evaluation for mandatory military service for all men in Norway. Intelligence scores were used as predictors of childlessness. Information on education, income and relationship history was retrieved from both the Young in Norway survey and the FD-trygd register. Mediation analyses with logistic regression analysis were performed in order to examine the direct and indirect effect of intelligence on childlessness.

Results: No linear association between intelligence and childlessness was found. However, follow-up analyses showed that higher risk of childlessness was associated with the highest stanine intelligence score (two standard deviations above the normed average), and that this effect was mediated by whether participants had ever been in a relationship by their late twenties. No significant direct effect of the highest stanine intelligence score was found when the question of whether participants had ever been in a relationship by their late twenties was included.

Conclusion: The present study revealed a complex association between intelligence and childlessness. The mediated association between the highest stanine intelligence score and childlessness was interpreted as an expression of delayed family formation. It is still unclear whether this delay in family formation will “catch up” if childlessness is measured at an older age, which raises the need for additional studies on the subject.

Widespread Gray Matter Gain 4-6 Weeks After Giving Birth: A restoration of brain tissue or a substantial brain reorganization, possibly to accommodate a multi-faceted repertoire of complex behaviors associated to being a mother

From Baby Brain to Mommy Brain: Widespread Gray Matter Gain After Giving Birth. Eileen Luders et al. Cortex, January 28 2020. https://doi.org/10.1016/j.cortex.2019.12.029

Abstract: Pregnancy results in obvious physiological changes to the female body, but data as to what happens to the maternal brain after giving birth are sparse as well as inconsistent. The overall goal of this study is to determine the nature of cerebral change in the postpartum period. For this purpose, we analyzed T1-weighted brain images of 14 healthy women (age range: 25 – 38 years) at two time points, specifically within 1-2 days of childbirth (immediate postpartum) and at 4-6 weeks after childbirth (late postpartum). When comparing voxel-wise gray matter between these two time points, there was no evidence of any significant decrease. Instead, we detected a pronounced gray matter increase involving both cortical and subcortical regions, such as the pre- and postcentral gyrus, the frontal and central operculum, the inferior frontal gyrus, the precuneus, and the middle occipital gyrus, as well as the thalamus and caudate. These structural changes occurring within only 4-6 weeks after delivery are reflective of a high degree of neuroplasticity and massive adaptations in the maternal brain. They may suggest a restoration of brain tissue following pregnancy and/or a substantial brain reorganization, possibly to accommodate a multi-faceted repertoire of complex behaviors associated with being a mother.

How Large Are Gender Differences in Toy Preferences? A Systematic Review and Meta-Analysis of Toy Preference Research

How Large Are Gender Differences in Toy Preferences? A Systematic Review and Meta-Analysis of Toy Preference Research. Jac T. M. Davis & Melissa Hines. Archives of Sexual Behavior, January 27 2020. https://link.springer.com/article/10.1007/s10508-019-01624-7

Abstract: It is generally recognized that there are gender-related differences in children’s toy preferences. However, the magnitude of these differences has not been firmly established. Furthermore, not all studies of gender-related toy preferences find significant gender differences. These inconsistent findings could result from using different toys or methods to measure toy preferences or from studying children of different ages. Our systematic review and meta-analysis combined 113 effect sizes from 75 studies to estimate the magnitude of gender-related differences in toy preferences. We also assessed the impact of using different toys or methods to assess these differences, as well as the effect of age on gender-related toy preferences. Boys preferred boy-related toys more than girls did, and girls preferred girl-related toys more than boys did. These differences were large (d ≥ 1.60). Girls also preferred toys that researchers classified as neutral more than boys did (d = 0.29). Preferences for gender-typical over gender-atypical toys were also large and significant (d ≥ 1.20), and girls and boys showed gender-related differences of similar magnitude. When only dolls and vehicles were considered, within-sex differences were even larger and of comparable size for boys and girls. Researchers sometimes misclassified toys, perhaps contributing to an apparent gender difference in preference for neutral toys. Forced choice methods produced larger gender-related differences than other methods, and gender-related differences increased with age.

Discussion

We found a broad consistency of results across the large body of research on children’s gender-related toy preferences: children showed large and reliable preferences for toys that were related to their own gender. Thus, according to our review, gender-related toy preferences may be considered a well-established finding. Our results, with 75 studies and a range of toy preference measurements, complement and extend a previous meta-analysis of 16 studies focused on free play (Todd et al., 2018).
However, our meta-analyses also revealed some gaps that could prevent confident inferences about the drivers and consequences of children’s gender-related toy preferences. These gaps could form priority targets for future research. Our analyses also revealed some emergent patterns in the data, especially in how gender-related preferences for broad groups of toys differed in some respects from those for dolls and vehicles, how study results varied according to study method, and how gender-related differences in toy preferences related to child age.

Toy Selection and Gender Categorization

The way that toys are selected, and categorized, as boy-related or girl-related, is not standardized in the present research. Studies in our review appeared to treat the gender categorization of toys as uncontroversial, even though, according to our review, it was not uncommon for toys to be assigned to different gender categories in different studies. For example, in some studies, blocks were classified as boy-related toys (e.g., Alexander & Saenz, 2012; Benenson et al., 1997; Fagot & Patterson, 1969), and in other studies they were classified as neutral toys (e.g., Cherney et al., 2003; Guinn, 1984; Wood, Desmarais, & Gugula, 2002). Similarly, drawing toys were sometimes categorized as girl-related toys (e.g., Berenbaum & Hines, 1992; Martin et al., 2013), and sometimes as neutral toys (e.g., Berenbaum & Snyder, 1995; Pasterski et al., 2005); and stuffed toys were equally likely to be classified as girl-related toys (e.g., DeLucia, 1963; Jacklin et al., 1973) as neutral toys (e.g., Alexander & Saenz, 2012; Idle et al., 1993; Moller & Serbin, 1996), but were also sometimes classified as boy-related toys (e.g., Stagnitti, Rodger, & Clarke, 1997). This pattern suggests that researchers sometimes disagree on what toys are boy-related, girl-related, or neutral.
In addition to finding that researchers sometimes disagreed on toy classifications, we also found that researchers typically did not report how they had selected toys for study or how they had assigned the toys to gender categories. We suspect that, in most cases, researchers used a simple heuristic method based on perceived cultural stereotypes. There are two problems with this type of approach. First, as noted above, toys categorized using this approach do not always fall into the same gender category in different studies. If one study includes a stuffed toy in the category “girls’ toys” and another study includes a stuffed toy in the category “neutral toys,” they may well report different results, even if the true underlying effect they are measuring is the same. Second, at its extreme, this problem may manifest as criterion contamination, in which gender-typed toys are defined by the results of the study. That is, the researchers may use many toys and select as “gender-related” toys the ones that they find to be differentially preferred by gender. At best, this tautology limits the generalizability of study results to other samples. At worst, it could invalidate the study.
Using methods that avoid confusion about toy categorization could be a priority for future research on children’s gender-related toy preferences. As also suggested by Fine (2015), this field could benefit from researchers specifying more clearly the ways in which they selected and categorized toys. Depending on the goal of the study, this selection and categorization might be based on different criteria. For example, a study examining whether stereotypes about children’s toy preferences relate to children’s actual preferences, might select toys based on adults’ independent ratings of the gender stereotyping of toys. In contrast, a study of the effect of a particular mechanism, such as social, cognitive, or hormonal influences, on toy preferences might select toys based on prior studies’ findings that certain toys are on average preferred by girls or boys. Overall, the important point is that researchers report more clearly how they selected toys and assigned toys to gender categories.
Researchers also have begun to investigate specific hypotheses about what characteristics of different toys might make them appeal more to boys or to girls. For instance, it has been suggested that color or shape might influence children’s gender-related preferences (e.g., Jadva et al., 2010; Weisgram et al., 2014; Wong & Hines, 2015). Similarly, it has been suggested that affordance of activity, motion, or propulsion might influence these preferences (Alexander & Hines, 2002; Benenson et al., 1997; Hassett et al., 2008; for a review, see Zosuls & Ruble, 2018). To evaluate these suggestions, it would be useful if researchers could provide color images, or full descriptions, of the toys used in the research they report. Similarly, it would be useful for this purpose, as well as for future reviews, if researchers could provide descriptive statistics, including means and SD or similar, by sex, for individual toys used, and not just for toy groupings.
To test whether the meta-analysis results were affected by researchers’ definitions of toy gender, we analyzed the subset of effect sizes that related to a very narrow definition of boy-related toys and girl-related toys: specifically, vehicles and dolls. These toys were the only ones for which sufficient data had been reported to allow reliable meta-analyses. The gender effects observed in the overall meta-analyses were broadly replicated with this more narrowly defined subset of toys, giving us confidence that our overall meta-analytic results were not entirely dependent on how researchers had chosen to categorize toys in regard to gender.
Furthermore, we found that girls’ gender-specific preference for dolls over vehicles was larger than their preference for broadly defined groups of girl-related toys. However, despite the large effect size, girls’ gender-specific preference for dolls over vehicles was not statistically significant, as this effect also showed large meta-analytic statistical variance. The large meta-analytic statistical variance is due to a combination of large variances in girls’ preference for dolls within the studies, variation between studies introducing additional statistical variance, and a smaller total number of studies that reported separate statistics for dolls as compared to broadly defined toy groups. In addition, the broadly defined toy groups included toys that, as mentioned above, were classified as neutral in some studies but girl-related in others. If toys are classified consistently, girls may show gender-related preferences at least as large as those of boys.

Culture and Gender-Related Toy Preferences

Cultural perceptions of play, including play with toys, may differ in different cultural, ethnic, or socioeconomic groups. For example, play is viewed as central to children’s cognitive and social development in many Western, technologically developed societies, but as less important in more traditional societies (Roopnarine, 2010). Children in different cultures may also have different referential concepts for appropriate gender-related behavior, due to cultural variation in gender norms (Pfeiffer & Butz, 2005; Wood & Eagly, 2002). This possibility is particularly relevant to toy preferences, because there may be cultural variations in the toys that are available, culturally relevant, and gender-related.
Nevertheless, little empirical research is presently available on cultural variation in gender-related toy preferences. Our review revealed that most toy preference studies focus on the U.S., Canada, the UK, and Australia. Of those studies conducted outside English-speaking industrialized nations, one was conducted in France (Le Maner-Idrissi, 1996), one in Finland (Lamminmäki et al., 2012), four in Sweden (Nelson, 2005; Nordenström, Servin, Bohlin, Larsson, & Wedell, 2002; Serbin et al., 2001; Servin, Bohlin, & Berlin, 1999), and one in the Netherlands (van de Beek et al., 2009). An additional study included some participants from Hungary, along with participants from the UK (Turner & Gervai, 1995). These studies did not report different results to the studies from the English-speaking countries, even when researchers had specifically hypothesized that they would (e.g., Nelson, 2005). In global perspective, however, these countries are very similar in terms of industrialization, wealth, education, media access, democracy, and gender equality. Consequently, children in these countries probably have very similar toys available to them and similar access to information about dominant social stereotypes around these toys. It remains an open question, then, whether children in cultures with radically different stereotype referents and social norms would show the same gender-related toy preferences to those found in the current meta-analysis.
We did not formally investigate other aspects of cultural diversity, such as ethnicity and socioeconomic status, because these also have not received much attention in empirical studies of gender-related toy preferences. Participants in most toy preference studies are not very ethnically diverse, and so it may not be practical to report results by ethnicity. We found three studies (out of our total 75) that reported toy preferences by ethnicity. Two of these studies were conducted in the USA and reported no significant differences in gender-related toy preferences between children of Hispanic and non-Hispanic background (Goble, 2012), or Native American and non-Native American background (Guinn, 1984). In contrast, another study based in the U.S. found that ethnicity might affect children’s preferences for gender-related activities, including play with toys, via children’s social networks (Martin et al., 2013). Furthermore, in recent years, the wider field of gender development research has paid increasing attention to the intersectionality of gender, ethnicity, and other identities (e.g., Shields, 2008). This trend in the wider field may translate in future to more studies investigating gender-related toy preferences in diverse social groups.

Methods of Measuring Toy Preference Are Important

Studies may find different gender effects on children’s toy preferences, depending on the method they use to measure toy preferences. We evaluated four categories of study methods: free play methods, where children were given access to a set of toys and observed playing, however, they liked; visual preference measures, where children were asked to look at pictures of toys; forced choice methods, where children were asked to choose toys or pictures of toys, typically in front of an experimenter; and naturalistic methods, where children’s toy options were not predefined by the researchers or other adults. We found that forced choice methods consistently showed larger gender differences than other methods.
There are two possible explanations for this pattern. One is the potential demand characteristics of forced choice paradigms. A request to publicly choose an option may be interpreted as evaluative by children, who then feel obliged to give the answer that they feel is “correct,” rather than indicate their actual preference. Children’s propensity to misunderstand requests for information as tests has been noted in other contexts (e.g., Lamb et al., 2003). Another possibility is that the paradigm creates a false dichotomy. In forced choice methods, the child is usually presented with one boy-related option and one girl-related option and asked to choose between them. There is usually not a neutral option, and, generally, the child must choose only one option and reject the other. In contrast, in a free play paradigm, children typically have more response options available, such as several toys associated with each gender, or neutral toys as well as gender-related toys. Even if only two toys are available, the child has more options than in most forced choice paradigms. For example, if a doll and a car are available, a child may choose to play with the doll, play with the car, play with both the doll and the car, or play with neither. In most forced choice methods, however, children must choose one and only one of two options.
Forced choice methods, in their current form, do not give comparable results to other methods of measuring gender-related toy preferences. Nevertheless, forced choice methods can be an efficient and easily administered measurement tool and therefore may be appropriate for studies where, for example, data need to be collected across a very large group or under difficult conditions. Future investigators wishing to measure gender-related toy preferences with an easily administered tool might do so, however, with the aim of minimizing artificial inflation in effect sizes. For instance, a procedure in which the experimenter cannot see which option the child selects, and the child knows that their response is not seen, might be useful. It also might be useful to include neutral options, as well as gender-related options, and allow the range of possible choices to include “both” or “neither.” These modifications of forced choice methods could provide results that are more comparable to other methods of measuring toy preference and perhaps are more reflective of children’s actual gender-related preferences.

Child Age and Gender-Related Toy Preferences

We found that gender differences in preferences for gender-related toys increased linearly with child age. Our results further suggested that this pattern could be explained by boys’ showing increased preference for gender-typical over gender-atypical toys with age, while girls’ preferences for gender-typical over gender-atypical toys did not increase significantly with age. Similarly, the previous meta-analysis of free play studies (Todd et al., 2018) found an increase in gender-related play with age in boys, although they did not find increasing gender differences. This may reflect a difference in the power of the two meta-analyses; the previous meta-analysis included 16 studies, whereas the current meta-analysis included 75 studies. We did not find significant curvilinear effects of age on children’s gender-related toy preferences.
Our findings of linear effects contrast with those of some prior investigations of age effects on children’s gender-related toy preferences. For example, Campbell et al. (2000) measured infants’ gender-related visual preferences longitudinally at ages 3, 9, and 18 months. They found that preferences did not change with age, but the infants were all very young compared to the age range in the wider literature and in the current meta-analysis.
In contrast, our meta-analytic findings suggest that boys’ and girls’ gender-related toy preferences increase with age in a linear fashion. These findings resemble findings for a broader measure of children’s gender-typical behavior, the Pre-School Activities Inventory (PSAI). The PSAI is a 24-item parent report inventory that asks about children’s gender-typed toy preferences and about children’s gender-related activity and playmate preferences. A longitudinal, population study in which the PSAI was completed by a parent to describe their child at ages 2, 3, and 5 years also found that both boys and girls became increasingly gender-typed with age (Golombok et al., 2008).
Our results suggest that children’s toy preferences might become more gender-related with age, as predicted by several theories of gender development. Children might be encouraged, through socialization pressures such as modeling and reinforcement, to prefer same gender-related toys, and the effects of this socialization may accumulate as they get older (Fagot, Rodgers, & Leinbach, 2000). Additionally, based on their early gender-related toy interests, children might gravitate to different social environments, enhancing their early preferences (Liben & Bigler, 2002; Martin et al., 2013). Finally, differences in children’s prenatal and early postnatal hormone exposure may dynamically interact with social environments and cognitive processes to increase children’s gender-related preferences over time (Hines, 2012). Together, these social and cognitive effects, and their interactions with early hormonal influences, may explain the linear increase in gender-related differences with age.
The findings of our meta-analysis, however, are not a substitute for a large, longitudinal study of children’s gender-related toy preferences. We used meta-analytic techniques to compare gender-related preferences in children from different age groups, reported in different studies. Our analysis, therefore, was cross-sectional and does not have the inferential power of a well-controlled longitudinal study. Our results would be best confirmed by a future longitudinal study of children’s gender-related toy preferences from infancy to pre-pubertal age. The longitudinal parent report study using the PSAI (Golombok et al., 2008) is the closest existing example and found similar results to our meta-analysis.

Gender-Related Toy Preferences Over Time

We found no change in the magnitude of gender-related differences in toy preferences across year of publication. The results of the moderator analyses suggested that gender effects on children’s toy preferences have remained generally constant in magnitude across the past five decades. This finding might seem surprising. Since the earliest studies on gender-related toy preferences, gender-atypical behavior and preferences have become increasingly socially acceptable. Perhaps the lack of any discernible pattern of change results from different social pressures influencing gender-related toy preferences in different directions. For example, growing acceptance of gender-atypical behavior may be countered by increasing gender segregation of the toy market.
Contrary to our results, a previous meta-analysis of children’s toy preferences (Todd et al., 2018) found that boys and girls played more with gender-related toys in earlier studies than in more recent studies. Todd et al. suggested that increasing gender equality in Western societies could influence children to play with neutral toys, due to increased advertising to children about gender-neutral toys. A recent analysis of online toy marketing, however, found that more toys were marketed for “boys only” or for “girls only” than for both (Auster & Mansbach, 2012), and an analysis of department store catalogs concluded that gender differentiation in toy advertising had increased since the 1980s as marketers employed gender stereotypes to encourage sales (Sweet, 2013). Taken together, these analyses challenge the view that gender-related toy advertising is decreasing with time. Alternatively, the previous finding could be partly explained by the smaller time frame considered in the prior meta-analytic review; the prior review covered about 35 years of research, while the present review covered 50 years.
It may be that children’s preferences are robust to social influences at this macrolevel; or that, despite social change, the underlying cultural environment regarding gendered toys has not changed. A similar result was found in a systematic review of gender stereotypes from the 1970s to the present. Rudman and Glick (2008) hypothesized that women’s changing social roles would be reflected in changing stereotypes of women. Although they found a change in women’s self-concept over time, they also found that more general stereotypes of women’s personalities had not changed. They suggested that the lack of change might be due to people viewing personality as part of the fundamental essence of gender, and therefore being reluctant to modify their stereotypic beliefs about personality. A similar explanation may also apply to toy preferences: if people view toy preferences as an essential part of a child’s gender, they may be unlikely to change their gender-related beliefs about toy preferences. Children may then adapt their actual toy preferences to reflect broader societal beliefs.

Limitations

The meta-analysis could only include data that were reported in the individual toy preference studies. Therefore, we could not analyze variables such as color or shape, or individual toys other than dolls and vehicles. In future research, if investigators report more information about toy characteristics and about individual toys, it may be possible to discover more about what characteristics of different toys make them more likely to be preferred by one gender or another.
Our literature search covers papers published to March 2014 and does not include papers published outside of this time frame. More recent papers may therefore be missing from the current meta-analysis. The current meta-analysis, however, synthesizes 50 years of research on toy preferences and finds that toy preference effect sizes have not changed significantly over time. Thus, results from a new review including more recent papers would be unlikely to differ from what we report.
We focused on gender-related preferences in typically developing children. Some studies selected participants specifically because they were not typically developing (for example, clinical samples of children with genetic variants causing atypical early hormone environments, or children who showed gender-related behavior that was noticeably different from their peers). To include these atypical populations in our study might have skewed the results, so we did not include them. Our results, therefore, may not apply to clinical populations.
Additionally, we meta-analyzed only direct measures of children’s toy preferences. We did not, for example, include parent report measures. Similarly, we did not include broader aspects of children’s gender-related behavior, such as activity preferences, playmate preferences, or sex role identification (e.g., Brown, 1956). Additionally, we did not search for these broader terms, so we may have missed papers that included toy preferences in a broader measure of sex role identification or androgyny (e.g., Zucker & Torkos, 1989). It would be interesting to know whether meta-analyses from these other sources of data and types of gender-related behavior would show similar outcomes. We hope that the current systematic review and meta-analysis will encourage such studies.

Intact microbiota is a key component of older males attractiveness; age-based preferences may break down when the microbiota is impaired, like when individuals are exposed to naturally occurring antibiotics, extreme temperatures

Drosophila Sexual Attractiveness in Older Males Is Mediated by Their Microbiota. Chloe Heys et al. Microorganisms 2020, 8(2), 168. Jan 22 2020. https://doi.org/10.3390/microorganisms8020168

Abstract: Age is well known to be a basis for female preference of males. However, the mechanisms underlying age-based choices are not well understood, with several competing theories and little consensus. The idea that the microbiota can affect host mate choice is gaining traction, and in this study we examine whether the male microbiota influences female preference for older individuals in the fruit fly Drosophila pseudoobscura. We find that an intact microbiota is a key component of attractiveness in older males. However, we found no evidence that this decrease in older male attractiveness was simply due to impaired microbiota generally reducing male quality. Instead, we suggest that the microbiota underlies an honest signal used by females to assess male age, and that impaired microbiota disrupt this signal. This suggests that age-based preferences may break down in environments where the microbiota is impaired, for example when individuals are exposed to naturally occurring antibiotics, extreme temperatures, or in animals reared in laboratories on antibiotic supplemented diet.

Keywords: age; Drosophila pseudoobscura; female choice; indirect benefits

The Mismeasure of Genes: No Support for the Genetic Hypothesis of the Black-white Achievement Gap Using Polygenic Scores and Tests for Divergent Selection

Bird, Kevin A. 2020. “The Mismeasure of Genes: No Support for the Genetic Hypothesis of the Black-white Achievement Gap Using Polygenic Scores and Tests for Divergent Selection.” SocArXiv. January 27. doi:10.31235/osf.io/2qfkt

Abstract: Protracted debates about the cause of an observed IQ gap between Black and white populations around the world have persisted within the fields of genetics, anthropology, and psychology for over a century. Newly available public genomic data have changed each of these fields in many ways; one side effect is that they have encouraged a new generation of race science. The current generation of race scientists claims that analysis of polygenic scores---generally computed as linear combinations of alleles identified by a genome-wide association study---provide evidence that a significant portion of differences in cognitive ability between Black and white people are caused by genetic differences, frequently claiming these differences came about due to divergent natural selection. In light of recent calls for cautious interpretation of polygenic-score analyses by geneticists, I apply the latest robust methods to detect genetic differentiation and polygenic selection that address known biases in polygenic-score analysis, testing the claim that genetic differences explains the gap in educational attainment and cognitive performance and that divergent selection has occurred between African and European populations. I show that past results were inflated by these biases and a more careful analysis provides strong evidence inconsistent with divergent selection and genetic differences driving the Black-white gap in cognitive ability.

Fever dreams were more bizarre & more negatively toned & included more references to health & temperature perception compared to normal dreams – findings that are in line with the continuity hypothesis of dreaming

Fever Dreams: An Online Study. Michael Schredl and Daniel Erlacher. Front. Psychol., January 28 2020. https://doi.org/10.3389/fpsyg.2020.00053

Abstract: In addition to a large variety of somatic symptoms, fever also affects cognition, sleep, and mood. In an online survey with 164 participants, 100 fever dream reports were submitted. Fever dreams were more bizarre and more negatively toned and included more references to health and temperature perception compared to “normal” most recent dreams – findings that are in line with the continuity hypothesis of dreaming. Future studies should follow up this line of research by conducting diary studies during naturally occurring febrile illnesses and sleep laboratory studies with experimentally induced fever. It would also be very interesting to study the effect of thermal stimulation applied during sleep on dream content. This research helps to understand subjective experiences while sleeping in an extreme condition (elevated body temperature).

Discussion

The present study indicates that fever affects dreaming; fever dreams are more bizarre – confirming the previous finding of our pilot study (Schredl et al., 2016b) in an independent sample – but also included more negative dream emotions, less dream characters and interactions, and more health-related topics and heat perceptions than the matched normal non-fever dreams. As fever dreams have not yet been studied systematically, it is reassuring that we were able to replicate the pilot findings with a new independent sample indicating that the present findings are substantial.

Before discussing the findings, several methodological issues will be addressed. First, fever dreams were elicited retrospectively, i.e., sometimes experienced quite some time ago. That might have biased the results as extraordinary dreams are more likely to be recalled after such long periods of time (Cipolli et al., 1992). However, the time interval between occurrence of the dream and its reporting was not related to emotional intensity or bizarreness. In addition, the dreams selected for comparison were also retrospectively recalled dreams. In order to test for possible recall effects using retrospective designs, it would be very interesting to use a prospective approach like Smith (2012b), i.e., hand out a dream diary and instruct the participants to complete this diary if they suffer from a febrile illness. However, one has to keep in mind that fever does not occur that often, so this study might be arduous. The retrospective nature of the study also does not allow any inferences regarding the sleep stage in which the dreams occurred. As fever can trigger episodes of sleepwalking (Avidan, 2017), one might speculate if, for example, the first dream example is a remembrance of a sleepwalking episode. Typically reports from NREM parasomnia episodes can include the bed chamber but are very brief (Arnulf, 2019), so the finding that fever dreams are generally comparable in length and even more bizarre than “normal” dreams indicates that those reports rarely reflect sleepwalking. However, content of sleepwalking episodes related to fever has never been studied systematically; the subjective experiences within these episodes might also be more bizarre compared to “normal” sleepwalking episodes. Due to the rare occurrence of fever episodes, ambulatory polysomnographic studies, i.e., recording the sleep stage prior to the reported dream, are very arduous. It would also be very interesting to study the effect of experimentally increasing body temperature by cytokines (cf. Reichenberg et al., 2001) on dream characteristics and content. Next, it should be noted that the sample consisted of high dream recallers; the mean dream recall frequency in the general population is about one morning per week with dream recall (Schredl, 2008) whereas in our study the mean dream recall frequency indicated dream recall several times a week. On the other hand, reporting a fever dream was not related to dream recall frequency but to the frequency of having fever. But one might argue that the reported percentages of experiencing fever dreams while being ill is an overestimation in this study due to overall heightened dream recall and, therefore, it would be necessary to carry out surveys in representative samples for obtaining data as to how often fever dreams occur.

The finding that fever dreams contain more intense negative emotions and less intense positive emotions supports the continuity hypothesis of dreaming as fever is also accompanied by more negative moods in waking (Reichenberg et al., 2001) and negatively toned dreams might reflect these negative waking emotions. This link between waking emotional tone and dream emotions has been shown in healthy persons (Schredl and Reinhard, 2009-2010). Also, Bódizs et al. (2008) found that poor health is related to more negatively toned dreams. To follow up this line of thinking, future studies could elicit mood during waking in persons with fever and test how strong waking emotions affect dreams while being ill. Similarly, it would be interesting to test whether the cognitive impairment in waking due to fever (Hall and Smith, 1996; Smith, 2012a) is directly related to dream bizarreness, i.e., are dreams of persons with more pronounced cognitive impairments more bizarre than dreams of persons with mild cognitive impairments during a febrile illness? The basic idea is that the “over-heated” brain is not functioning properly and, therefore, dreams are more bizarre. In schizophrenic patients, for example, the severity of psychotic symptoms during the day is directly related to dream bizarreness (Schredl and Engelhardt, 2001).

Also in line with the continuity hypothesis is the finding that fever dreams included more health-related topics. A previous study in patients with insomnia (Schredl et al., 1998b) showed that more health problems are associated with more health-related dreams. Interestingly, the frequency of health-related dreams is not only related to the frequency of the illnesses but also to worrying about health (Schredl et al., 2016a), i.e., future studies might also include this variable.

Interestingly, the findings of less dream characters and less physical and verbal Interactions also fit in the continuity hypothesis because one of the accompanying behavioral changes of fever is social withdrawal (Harden et al., 2015).

Lastly, fever dreams included more references to temperature perception (see the illustrative second dream example) than non-fever dreams. In a long dream series, explicit temperature perceptions were present in only in 0.63% of the dreams (Schredl, 2016). This increased number of temperature perceptions in fever dreams might reflect the waking-life experience of feeling hot, within the framework of the continuity hypothesis, but it is also plausible that the fever dreams might be affected by the internal sensation of feeling hot while sleeping. Research has shown that external stimuli like sounds, water spray, rocking of the bed, and mild pain stimuli are sometimes incorporated into dreams (Dement and Wolpert, 1958; Nielsen et al., 1993; Leslie and Ogilvie, 1996). Interestingly, somatosensory stimulation of the leg muscles was incorporated into dreams quite often and could result in bizarreness related to the body image (Nielsen, 1993); the dream examples might also reflect a very creative processing of the internal heat stimulus. However, studies on the effect on dreams of thermal stimulation, e.g., thermal stimuli applied to the skin, have not yet been performed. If heat stimuli are incorporated into dreams, the hypothesis that fever directly affects dreams via the increased body temperature would be supported.

To summarize, this study showed that fever dreams are quite common and differ significantly from non-fever dreams, i.e., fever dreams were more bizarre, more negatively toned and included more references to health and temperature perception. Future studies should follow up this line of research by conducting diary studies during naturally occurring febrile illnesses and sleep laboratory studies with experimentally induced fever. This research helps to understand subjective experiences while sleeping in an extreme condition.

Sub-par embryos are terminated automatically; embryos improve test performance by exaggerating formerly honest quality signals; new honest indicators arise while old degraded indicators linger

Embryo Selection and Mate Choice: Can ‘Honest Signals’ Be Trusted? Dakota E. McCoy, David Haig. Trends in Ecology & Evolution, January 28 2020. https://doi.org/10.1016/j.tree.2019.12.002

Highlights
.    Mate choice by honest signaling is a classic explanation for elaborate traits in nature. Many researchers have: (i) observed deceptive signaling, and (ii) wondered how honest signals relate to trait elaboration.
.    Honest signaling is analogous to high-stakes testing. Quality is hard to measure directly, so proxies (tests) are used. High-stakes testing causes ‘teaching to the test’ without improving educational outcomes.
.    Embryo choice is another high-stakes test. Mothers select healthy embryos and terminate sub-par embryos automatically. Embryos are selected to pass maternal tests without improving their quality. The resulting arms race causes extreme and elaborate signals during pregnancy.
.    We can better understand elaborate traits in nature if we interpret mate selection, and embryo choice, as a dynamic give-and-take between two parties with conflicting fitness interests.

Abstract: When a measure becomes a target, it often ceases to be a good measure – an effect familiar from the declining usefulness of standardized testing in schools. This economic principle also applies to mate choice and, perhaps surprisingly, pregnancy. Just as females screen potential mates under many metrics, human mothers unconsciously screen embryos for quality. ‘Examinees’ are under intense selection to improve test performance by exaggerating formerly ‘honest’ signals of quality. Examiners must change their screening criteria to maintain useful information (but cannot abandon old criteria unilaterally). By the resulting ‘proxy treadmill’, new honest indicators arise while old degraded indicators linger, resulting in trait elaboration and exaggeration. Hormone signals during pregnancy show extreme evolutionary escalation (akin to elaborate mating displays).