Thursday, November 26, 2020

The Heritability of Insomnia Is Approx 40pct: A Meta‐Analysis of Twin Studies

The Heritability of Insomnia: A Meta‐Analysis of Twin Studies. Nicola L. Barclay  Desi Kocevska  Wichor M. Bramer  Eus J. W. Van Someren  Philip Gehrman. Genes, Brain and Behavior, November 21 2020.

Rolf Degen's take:

Abstract: Twin studies of insomnia exhibit heterogeneity in estimates of heritability. This heterogeneity is likely due to sex differences, age of the sample, the reporter, and the definition of insomnia. The aim of the present study was to systematically search the literature for twin studies investigating insomnia disorder and insomnia symptoms and to meta‐analyse the estimates of heritability derived from these studies to generate an overall estimate of heritability. We further examined whether heritability was moderated by sex, age, reporter and insomnia symptom. A systematic literature search of 5 online databases was completed on January 24th 2020. Two authors independently screened 5,644 abstracts, and 160 complete papers for the inclusion criteria of twin studies from the general population reporting heritability statistics on insomnia or insomnia symptoms, written in English, reporting data from independent studies. We ultimately included 12 papers in the meta‐analysis. The meta‐analysis focussed on twin intra‐class correlations for monozygotic and dizygotic twins. Based on these intra‐class correlations, the meta‐analytic estimate of heritability was estimated at 40%. Moderator analyses demonstrated stronger heritability in females than males; and for parent‐reported insomnia symptoms compared to self‐reported insomnia symptoms. There were no other significant moderator effects, though this is likely due to the small number of studies that were comparable across levels of the moderators. Our meta‐analysis provides a robust estimate of the heritability of insomnia which can inform future research aiming to uncover molecular genetic factors involved in insomnia vulnerability.

Why do so few people share fake news? It hurts their reputation

Why do so few people share fake news? It hurts their reputation. Sacha Altay, Anne-Sophie Hacquin, Hugo Mercier. New Media & Society, November 24, 2020.

Abstract: In spite of the attractiveness of fake news stories, most people are reluctant to share them. Why? Four pre-registered experiments (N = 3,656) suggest that sharing fake news hurt one’s reputation in a way that is difficult to fix, even for politically congruent fake news. The decrease in trust a source (media outlet or individual) suffers when sharing one fake news story against a background of real news is larger than the increase in trust a source enjoys when sharing one real news story against a background of fake news. A comparison with real-world media outlets showed that only sources sharing no fake news at all had similar trust ratings to mainstream media. Finally, we found that the majority of people declare they would have to be paid to share fake news, even when the news is politically congruent, and more so when their reputation is at stake.

Keywords: Communication, fake news, misinformation, political bias, reputation, social media, source, trust

Check also It happened to a friend of a friend: inaccurate source reporting in rumour diffusion. Sacha Altay, Nicolas Claidière and Hugo Mercier. Evolutionary Human Sciences, 22020, e49, November 2020.

Questions are raised regarding the plausibility of certain reports with effect sizes comparable to, or in excess of, the effect sizes found in maximal positive controls

Maximal positive controls: A method for estimating the largest plausible effect size. Joseph Hilgard. Journal of Experimental Social Psychology, Volume 93, March 2021, 104082.


• Some reported effect sizes are too big for the hypothesized process.

• Simple, obvious manipulations can reveal which effects are too big.

• A demonstration is provided examining an implausibly large effect.

Abstract: Effect sizes in social psychology are generally not large and are limited by error variance in manipulation and measurement. Effect sizes exceeding these limits are implausible and should be viewed with skepticism. Maximal positive controls, experimental conditions that should show an obvious and predictable effect, can provide estimates of the upper limits of plausible effect sizes on a measure. In this work, maximal positive controls are conducted for three measures of aggressive cognition, and the effect sizes obtained are compared to studies found through systematic review. Questions are raised regarding the plausibility of certain reports with effect sizes comparable to, or in excess of, the effect sizes found in maximal positive controls. Maximal positive controls may provide a means to identify implausible study results at lower cost than direct replication.

Keywords: Violent video gamesAggressionAggressive thoughtPositive controlsScientific self-correction

5. General discussion

Maximal positive controls can provide a cost-effective way to establish the upper bound of plausible effect sizes in a measure. These upper bounds can be useful in detecting errors in previously published literature. Although implausibly large effect sizes may indicate errors in data collection, errors in analysis, or even possible misconduct, it has been my experience that journals are reluctant to issue expressions of concern for implausibly large results. This reluctance may be caused by the difficulty in determining which results are “too big”—a subjective decision that depends on the judgments and expectations of individual researchers and editors. These individual judgments may be better aligned through the empirical support provided by the collection of maximal positive controls. In this way, maximal positive controls might help identify erroneous reports by providing an empirical estimate of how big is too big.

The three examples provided here revealed some possibly erroneous reports. Study 1 suggests that even the largest effect sizes observed on the story completion task should nevertheless be smaller than those repeatedly reported by Hasan et al., 2012Hasan et al., 2013Hasan et al., 2015. This indicates some manner of confound or error in the study. Because of this likely error, it is not clear that the inferences from Hasan et al. (2013) are correct: Violent video games might not increase hostile-world beliefs and aggressive behavior, hostile-world beliefs might not mediate effects of violent games on aggressive behavior, and effects of violent video games (if any) might not accumulate from day to day. To my knowledge, the only other such long-term experiment was that of Kühn et al. (2019), who observed that two months of Grand Theft Auto V caused an increase in word completion task scores, but no significant increase on a measure of aggressive world view, an aggressive-cognition lexical decision task, or the Buss-Perry aggression questionnaire. New research will be necessary to test these claims.

Study 3 similarly suggests that even the strongest aggressive-emotion Stroop effect should not exceed about 400 ms. A review of the literature finds a few aggression-emotion Stroop differences of comparable or greater magnitude (Smeijers et al., 2018Sun et al., 2019). There may be value in double-checking the accuracy of these reports.

In Study 2, by contrast, no studies using the word completion task approached the large effects found using maximal positive controls. Although individual differences in verbal skill may still represent a source of nuisance variance in this task, such differences do not seem to substantially limit the effect sizes one could obtain on this measure.

Researchers using these tasks may benefit from considering the effect size estimates in this study as benchmarks. For example, in the story completion task, if the difference between a peaceful architect and a mass murderer is d = 2.5, and the difference between that architect and an extreme sports enthusiast is d = 1.3, researchers should expect to find smaller effect sizes when using subtler manipulations and asking about the task's usual generic characters like “Todd” and “Jane.” Similarly, in the aggressive emotion Stroop, researchers should expect to find emotion Stroop effects of no more than 400 ms. When researchers estimate how many trials per participant or participants per study they should collect, reference to these estimates may help to inform power analyses by suggesting firm upper limits on even the most optimistic of effect size estimates. In the future, researchers may be able to develop heuristics about the typical ratio between an effect size observed in maximal positive control and in primary research.

One last practical suggestion can be made regarding the administration of the story completion task. Researchers can benefit from considering the influence of the different story stems, which elicited different mean scores. Although it is desirable to use multiple task stimuli to improve the task's generalizability, failing to model the effects of stimulus will leave those effects as error variance, reducing the effect size and degrading study power. The Condition × Scenario interaction suggests that the car accident scenario may be more sensitive than the other scenarios, perhaps by avoiding a floor effect.

Researchers are encouraged to use maximal positive controls to inspect the plausibility of effect sizes reported in their literatures. Maximal positive controls may be collected at lower cost than direct replications. Because maximal positive controls are deliberately dissimilar from original studies, they may also avoid some concerns common to direct replications such as omitted moderators (Stroebe & Strack, 2014), contextual sensitivity of effects (Van Bavel, Mende-Siedlecki, Brady, & Reinero, 2016), or the presence or absence of researcher “flair” (Baumeister, 2016). These concerns may avoided when there is a strong logical case that the maximal positive control should yield an effect strictly larger than the original work. Through the use of this method, researchers may learn more about the properties of their measurements, the range of plausible effect sizes, and the quality of research data, thereby facilitating faster scientific self-correction and improving the quality of data used in theory development.

Wednesday, November 25, 2020

The Comparative Impact of Cash Transfers and a Psychotherapy Program on Psychological and Economic Well-being

The Comparative Impact of Cash Transfers and a Psychotherapy Program on Psychological and Economic Well-being. Johannes Haushofer, Robert Mudida & Jeremy P. Shapiro. NBER Working Paper 28106, November 2020. DOI 10.3386/w28106

Abstract: We study the economic and psychological effects of a USD 1076 PPP unconditional cash transfer, a five-week psychotherapy program, and the combination of both interventions among 5,756 individuals in rural Kenya. One year after the interventions, cash transfer recipients had higher consumption, asset holdings, and revenue, as well as higher levels of psychological well-being than control households. In contrast, the psychotherapy program had no measurable effects on either psychological or economic outcomes, both for individuals with poor mental health at baseline and others. The effects of the combined treatment are similar to those of the cash transfer alone.

COVID-19: 91pct of stories by US major media outlets are negative in tone vs 65pct for scientific journals; stories of increasing cases are 5.5x stories of decreasing cases even when new cases are declining

Why Is All COVID-19 News Bad News? Sacerdote, Bruce and Sehgal, Ranjan and Cook, Molly. National Bureau of Economic Research, Working Paper 28110, Nov 2020.

Abstract: We analyze the tone of COVID-19 related English-language news articles written since January 1, 2020. Ninety one percent of stories by U.S. major media outlets are negative in tone versus fifty four percent for non-U.S. major sources and sixty five percent for scientific journals. The negativity of the U.S. major media is notable even in areas with positive scientific developments including school re-openings and vaccine trials. Media negativity is unresponsive to changing trends in new COVID-19 cases or the political leanings of the audience. U.S. major media readers strongly prefer negative stories about COVID-19, and negative stories in general. Stories of increasing COVID-19 cases outnumber stories of decreasing cases by a factor of 5.5 even during periods when new cases are declining. Among U.S. major media outlets, stories discussing President Donald Trump and hydroxychloroquine are more numerous than all stories combined that cover companies and individual researchers working on COVID-19 vaccines.

Weak consistency between self-reported emotional states by expressers and their facial emotional displays; low accuracy both of human perceivers and of the automatic classifier to infer subjective feelings

The emotion–facial expression link: evidence from human and automatic expression recognition. Anna Tcherkassof & Damien Dupré. Psychological Research, November 24 2020.

Abstract: While it has been taken for granted in the development of several automatic facial expression recognition tools, the question of the coherence between subjective feelings and facial expressions is still a subject of debate. On one hand, the “Basic Emotion View” conceives emotions as genetically hardwired and, therefore, being genuinely displayed through facial expressions. Consequently, emotion recognition is perceiver independent. On the other hand, the constructivist approach conceives emotions as socially constructed, the emotional meaning of a facial expression being inferred by the perceiver. Hence, emotion recognition is perceiver dependent. In order (1) to evaluate the coherence between the subjective feeling of emotions and their spontaneous facial displays, and (2) to compare the recognition of such displays by human perceivers and by an automatic facial expression classifier, 232 videos of expressers recruited to carry out an emotion elicitation task were annotated by 1383 human perceivers as well as by Affdex, an automatic classifier. Results show a weak consistency between self-reported emotional states by expressers and their facial emotional displays. They also show low accuracy both of human perceivers and of the automatic classifier to infer the subjective feeling from the spontaneous facial expressions displayed by expressers. However, the results are more in favor of a perceiver-dependent view. Based on these results, the hypothesis of genetically hardwired emotion genuinely displayed is difficult to support, whereas the idea of emotion and facial expression as being socially constructed appears to be more likely. Accordingly, automatic emotion recognition tools based on facial expressions should be questioned.

Number of live births predicts biological age acceleration in post‑menopausal, but not pre‑menopausal, women

Parity predicts biological age acceleration in post‑menopausal, but not pre‑menopausal, women. Talia N. Shirazi, Waylon J. Hastings, Asher Y. Rosinger & Calen P. Ryan. Scientific Reports (2020) 10:20522. Nov 2020.

Abstract: Understanding factors contributing to variation in ‘biological age’ is essential to understanding variation in susceptibility to disease and functional decline. One factor that could accelerate biological aging in women is reproduction. Pregnancy is characterized by extensive, energetically‑costly changes across numerous physiological systems. These ‘costs of reproduction’ may accumulate with each pregnancy, accelerating biological aging. Despite evidence for costs of reproduction using molecular and demographic measures, it is unknown whether parity is linked to commonly‑used clinical measures of biological aging. We use data collected between 1999 and 2010 from the National Health and Nutrition Examination Survey (n= 4418) to test whether parity (number of live births) predicted four previously‑validated composite measures of biological age and system integrity: Levine Method, homeostatic dysregulation, Klemera–Doubal method biological age, and allostatic load. Parity exhibited a U‑shaped relationship with accelerated biological aging when controlling for chronological age, lifestyle, health‑related, and demographic factors in post‑menopausal, but not pre‑menopausal, women, with biological age acceleration being lowest among post‑menopausal women reporting between three and four live births. Our findings suggest a link between reproductive function and physiological dysregulation, and allude to possible compensatory mechanisms that buffer the effects of reproductive function on physiological dysregulation during a woman’s reproductive lifespan. Future work should continue to investigate links between parity, menopausal status, and biological age using targeted physiological measures and longitudinal studies.

The Dutch on How Rich is Too Rich? Most do not consider extreme wealth itself a severe problem & object to the government’s enforcement of limits to wealth & income, but widespread support exists for increased taxation

How Rich is Too Rich? Measuring the Riches Line. Ingrid Robeyns, Vincent Buskens, Arnout van de Rijt, Nina Vergeldt & Tanja van der Lippe. Social Indicators Research, Nov 25 2020.

Rolf Degen's take:

Abstract: Is it possible to identify a ‘riches line’, distinguishing the ‘rich’ from the ‘super-rich’? Recent work in political philosophy suggests that this is theoretically possible. This study examines for the first time the empirical plausibility of a riches line, based on novel data collected from a representative sample of the Dutch population. The data reveal that the Dutch indeed draw such a line, namely between 1 and 3 million euros. Strikingly, respondents agree on its approximate location irrespective of their own income and education. Although most do not consider extreme wealth itself a severe problem and object to the government’s enforcement of limits to wealth and income, widespread support exists for increased taxation of the super-rich if that would improve the quality of life of the most vulnerable members of society.

Conclusions and Discussion

The data used in this study is the very first attempt of which we are aware that aims to establishing a riches line using judgements of people using a quantitative approach.Footnote3 Hence it must be seen as the first in a series of empirical studies looking into the evaluative question of whether society believes that there is an upper limit to how much wealth can contribute to the standard of living of a family, and the normative question of whether society thinks such an upper limit should be reinforced.

The first conclusion is that it is indeed possible to establish a riches line empirically. There appears to be a clear difference what “rich” and “super rich” means for people. Similar to the poverty line, this riches line proves to be a social construct. An implication is that politicians can use the riches line to discuss the level of riches in society, in a similar way as is already done in discussions about the poverty line. The evaluative claim which indicates that people can estimate what is super rich is thus supported. A riches line has already been developed in previous work based on the income distribution (Medeiros 2006; Concialdi 2018). We now have developed one which is based on judgements of people themselves.

The second conclusion is that such a riches line is not necessarily a norm for people. They do not perceive extremely rich people as a problem in itself. When a statement is presented in the abstract, not many people are in support of limiting extreme riches. By the same token, we can also conclude that a larger share of the population has a problem with riches when the statement is made concrete by means of a real-life situation. People thus appear in support of measures to limit riches when presented with specific cases of extraordinary wealth, and also when the societal gains from such limits are made salient. Most people are in support of a tax on the incomes of the super-rich if they are also told what that money will be used for—and if that money benefits the most vulnerable people in society.

The instrument we have shown seems to be able to establish how a certain population (in this case a representative sample of people in the Netherlands) thinks about where a riches line should be and at what point there might even be broad consensus that the riches line is reached. One advantage of our vignette method is that we provide respondents with an illustrative description of wealth of families rather than providing just a number of income or capital. We believe that this way of picturing helps respondents to judge richness more easily. In addition, the data have shown that the vignettes are also rightly chosen: we have quite fine-tuned distinctions around where respondents indicate that the riches line should be, while we also include the extremes where hardly any respondents think such a family is too rich or where almost everyone holds that such a family is too rich.

Clearly, the disadvantage of an illustrative instrument as this is that it is rather context dependent. The descriptions and variations used here might be reasonable for countries that have a similar welfare state infrastructure as the Netherlands. Countries with a significantly different type of welfare state, for example with a health care system or educational system that has a significant private sector, or without public pension provisions, might need to add those items to the vignettes in the questionnaire. In addition, the descriptions should be certainly adjusted if one were to use a similar methodology in less developed countries. This also implies that the outcomes might be used to guide politics within a certain country, but the method is less suitable to guide more global distributional questions. The context-relative nature of the measures we have adopted also implies that when societies change drastically over time, the measure might require adaption. At a methodological level, it should be noted that this vignette based set-up is flexible and easily adaptable to settings that require different variables while the essence of the analyses can remain the same. Finally, it is important to stress that this empirical method reveals the views by a population of people on when a person can be qualified as ‘extremely rich’, but does not directly address normative questions as to what reasons we might have for considering someone too rich, let alone what (if anything) would follow for policies.

Future research should take further steps towards refining the methodology for constructing and measuring the riches line. One question is whether mixed quantitative–qualitative methods, such as Q-methodology, would confirm the appropriateness and validity of quantitative surveys such as the one designed for this study. After we completed our study, a Report was published in which the idea of riches line was tested empirically with focus groups in London (Davis et al. 2020). One interesting line of future research would be to apply both the qualitative methods used in that study with the quantitative methods used in our study, and analyze possible differences in the results.

A second topic for further research relates to the context-sensitivity of absolute riches lines. To what extent does this make comparisons between the phenomenon of ‘superriches’ in different countries difficult, and how exactly? As we argued above, the content of the vignettes needs adapting in case the method we proposed is used in significantly different contexts. But what does this imply for intertemporal and international/interregional comparisons of studies of riches? Are they simply impossible, or are the merely difficult, and if so, what makes them (im-)possible? This study focused on the Netherlands, and it would be very interesting to investigate how the methodology can be generalized for different countries and to study whether it would be possible to quantify by means of an international comparative study to what extent the riches line depends on the economic development, policies and culture of a country.

In addition, subsequent research may probe the robustness of the tentative relationship between descriptive judgements and normative judgements identified here. Others may investigate whether public support for government policies imposing a riches line would be greater if concrete benefits of such policies were specified. Citizens may be unwilling to support policies that limit a person’s wealth if it is unclear what society would gain. Future studies may also make a clearer distinction between inequality generated by processes that people see as unfair and processes experienced as fair, such as income from employment being taxed differently than income from business activity (profit) or from capital gain. People may find ‘fairness’ important, which may not always be the same as ‘equality’ (Starmans et al. 2017).

Seniors Across Europe: The value of the car is, among all wealth components (houses, bank account, bonds, stocks, mutual funds, debts and mortgages), the form of wealth most related to life satisfaction

The Rolling 50s (and More): Cars and Life Satisfaction Among Seniors Across Europe. Gaël Brulé, Laura Ravazzini & Christian Suter. Applied Research in Quality of Life, November 24 2020.

Rolf Degen's take:

Abstract: Cars represent a valuable real asset that most individuals use on a daily basis. Although cars are a form of material prosperity like income and other forms of wealth, the link between cars and subjective well-being (SWB) is barely covered in the existing literature. Furthermore, few existing contributions are scattered across specific cultural contexts. Here, we analyze the relationship between cars and the SWB of seniors in different European countries using the SHARE dataset. We construct multilevel and fixed-effect models to explore the extent of economic, infrastructural, and cultural factors and how they can explain this relationship. The results show that the value of the car is, among all wealth components (houses, bank account, bonds, stocks, mutual funds, debts and mortgages), the form of wealth most related to life satisfaction. In addition, cars matter less (a) in affluent societies, (b) where rail infrastructure is more developed, and (c) where people hold fewer materialistic values. We discuss these results in the framework of the functional and positional value of cars, i.e., respectively, the value derived from it regardless of others and the value derived from it vis-à-vis others.


We found that cars have a significant and positive influence on the happiness of seniors in Europe. Their contribution is higher than housing wealth, money available for current expenditures, and other financial assets. This relationship between cars and SWB is observable in every European nation at different intensities. Differences across countries are linked to economic, infrastructural, and cultural factors. The relationship is also observed in longitudinal models. This increase is moderated by the level of affluence of the country: If there is economic growth, then an increase in car value becomes less important for SWB.


The Influence of the Context on the Relation Between Cars and SWB

One of the main findings of this paper is that the influence of cars matters more in less affluent countries although the relation is far from being systematic. Although seniors in countries such as Denmark enjoy having a more expensive car, they do so to a lesser extent than seniors in less affluent countries such as Greece. Part of this can be explained by the quality of infrastructures especially train infrastructure. Cars matter less in places where train infrastructures are better. Besides economic and infrastructural reasons, one can also see that values have an influence on the car-SWB relation. In countries where material possessions are more valued, owning an expensive car brings more happiness. Once introduced, the interaction term between importance of being successful and car value as well as the interaction term between importance of being rich and car value make the car-SWB relation insignificant. This also means part of the relation is carried out by values.

Contrary to the contribution of Okulicz-Kozaryn et al. (2015) in the USA, it seems that in Europe, having a more expensive car than an average frugal car is influential for seniors’ SWB. However, there is a difference between the two studies in the population studied; Okulicz-Kozaryn et al. (2015) observed the entire population while we only examined seniors. Materialistic values are more prominent among older generations (Inglehart 2008); this is likely to have an influence. Furthermore, public transportation is more developed in Europe than in the USA, and the effect of cars in Europe is probably more positional because the functional value can be derived by other means of transportation.

Functional Value or Positional Value

Hirsch (1976) distinguishes the functional value from the positional value of goods in general. We defined the functional value of cars as a driving unit and the positional value as anything that would come on top. Thus defined, this means that households owning a car can benefit from the functional value of the car, and the positional value is represented by the relative value of the car. In this case, a more expensive car has a higher positional value than a cheaper one independent of the type of car other people own. Our analysis shows that both the functional and positional values of a car have independent and additive effects on the life satisfaction of seniors. Individuals benefit from having a car, and more expensive cars bring more satisfaction. Here, there are two ways in which we operationalized the positional value of cars: (1) by looking at the national average car value and 2) by looking at the top 25% of car value in each country. These values are considered to be average and do not include the individual passion for driving that some people would consider as pleasure and is not necessarily positional. Furthermore, functional and positional values might not be fixed concepts; functional and positional value could evolve with economic growth or technological evolutions. What used to once be considered functional and positional values might become simply functional after some time once the item is considered to be “normal” (e.g., air conditioning in European countries).

Tuesday, November 24, 2020

Rolf Degen summarizing... The greater the emphasis countries placed on high achievement, the lower was the interest in math schoolwork, particularly among girls

Gender Differences in the Interest in Mathematics Schoolwork Across 50 Countries. Kimmo Eriksson. Front. Psychol., November 25 2020.

Rolf Degen's take:

Abstract: Although much research has found girls to be less interested in mathematics than boys are, there are many countries in which the opposite holds. I hypothesize that variation in gender differences in interest are driven by a complex process in which national culture promoting high math achievement drives down interest in math schoolwork, with the effect being amplified among girls due to their higher conformity to peer influence. Predictions from this theory were tested in a study of data on more than 500,000 grade 8 students in 50 countries from the 2011 and 2015 waves of TIMSS. Consistent with predictions, national achievement levels were strongly negatively correlated with national levels of math schoolwork interest and this variation was larger among girls: girls in low-achievement, high-interest countries had especially high interest in math schoolwork, whereas girls in high-achievement, low-interest countries had especially low interest in math schoolwork. Gender differences in math schoolwork interest were also found to be related to gender differences in math achievement, emphasizing the importance of understanding them better.


The present paper studied the difference between girls and boys in their interest in math schoolwork and how it varies across countries. A theory was proposed according to which national culture promoting high math achievement drives down interest in math schoolwork, but more among girls than among boys due to conformity to peer influence being stronger among girls. Moreover, I argued that gender differences in math schoolwork interest are important because they will contribute to gender differences in math achievement. In the absence of experimental data, I tested the predictions this theory makes about statistical observations in cross-sectional data, provided by TIMSS. Results were consistent with predictions, as detailed below.

First, an extremely strong negative correlation between national levels of achievement and math schoolwork interest was observed. This finding, which is well in line with prior research on the relation between national achievement levels and attitudes to math and science (Shen and Tam, 2008Täht et al., 2014), is consistent with the hypothesis that students’ interest in schoolwork is negatively influenced by the high educational norms and standards in high-achievement cultures (Van de gaer et al., 2012). That high-achievement culture may be killing students’ interest is arguably a serious problem. Comparisons between high-achieving countries indicate that the problem might be solvable, however. In a study of TIMSS data from 1999 to 2003, Shen and Tam (2008) pointed out that students in Singapore, an extremely high-achieving country, nonetheless had relatively positive attitudes toward math and science. Leung (2002) made the same observation. Singapore was a positive exception also in the current study, having the highest achievement level of all countries in the study, yet exhibiting a much higher national level of interest in math schoolwork than similarly high-achieving Korea and Japan did (Table 1). It would be valuable to understand whether there is some specific feature of Singapore’s school system that mitigates the negative side effects of a high-achievement culture.

Second, several findings were consistent with the hypothesis that conformity to peer influence on math schoolwork interest is higher among girls than among boys. In almost all countries in the study, within-society variation in math schoolwork interest was smaller among girls than among boys, thus indicating greater female conformity. Because societies vary in their average level of interest in math schoolwork, the effect of peer pressure will vary too. Consistent with greater susceptibility to peer influence among girls, between-society variation in math schoolwork interest was larger among girls than among boys (Figure 2): In countries where the interest in math schoolwork was low, it tended to be especially low among girls. Similarly, in countries where the interest in math schoolwork was high, it tended to be especially high among girls. Thus, the country variation in students’ interest in mathematics schoolwork was amplified among girls. The same phenomenon could be observed in terms of a positive correlation between national levels of math schoolwork interest and gender differences in math schoolwork interest favoring girls.

Taken together, my theory proposes a pathway in which high-achievement culture drives down schoolwork interest, which through differential peer influence creates gender gaps in interest disfavoring girls. Consistent with this pathway, I found a negative correlation between national levels of achievement and gender gaps in math schoolwork interest favoring girls, and this correlation was mediated by the national level of math schoolwork interest.

Why is it important how girls’ and boys’ interest in math schoolwork vary across countries? For one thing, it is theoretically important to realize that the variation is substantial. In countries like Japan, Hong Kong, Sweden, and New Zealand, the interest level of the average girl was about 0.2 standard deviations lower than the interest of the average boy. These findings are consistent with research arguing for a fundamental gender difference in subject interest (e.g., Su et al., 2009). But this view appears to be contradicted by the finding of other societies, such as Oman, Malaysia, Palestine, and Kazakhstan, in which the gender gap is at least as wide but reversed.

Gender differences in math interest may also have real-life implications by influencing how girls achieve in mathematics relative to boys in the same country. Consistent with this hypothesis, I found that variation in the gender gap in math schoolwork interest accounts for part of the proportion of variance in the gender gap in math achievement that is not explained by variation in gender egalitarian values (Eriksson et al., 2020).

This study is an example of the benefits of using big data from large-scale assessments of student achievement to examine phenomena in educational psychology. A limitation, inherent in the reliance on cross-sectional data, is that directions of causality are not established. The findings are consistent with the proposed theory, but they could also have arisen from other mechanisms. It is helpful to consider what these alternative mechanisms could be. With respect to the strong negative correlation between national levels of achievement and schoolwork interest, it seems implausible that it would arise from low interest levels having a positive effect on achievement levels. Following Van de gaer et al. (2012), I proposed that high educational norms and standards have lower interest as an undesired side effect. However, there might be something else going on and perhaps more detailed insights into the abovementioned differences between Singapore and its East Asian neighbors could shed more light on this.

Similar reasoning applies to the amplification among girls of national variation in schoolwork interest. I proposed that this arises from differential conformity to peer influence, but it cannot be excluded that there is some alternative societal factor that causes girls’ interest levels to be more extreme than the interest levels of boys. An interesting possibility for future research would be for large-scale assessments to provide some direct measures of peer influence (see also Eriksson et al., 2020).

The idea of conceiving of high-achievement culture as a factor behind gender differences has a precedent. In a study of PISA data, Mann and DiPrete (2016) found that the national achievement level correlated with gender differences in academic self-concept and STEM aspirations. However, they did not examine the female amplification account, that is, whether these effects were mediated by national levels of academic self-concept and STEM aspirations. Future research should examine the scope of female amplification as a mechanism behind gender differences in various beliefs and attitudes.

To conclude, the present study has contributed to scientific understanding of gender differences in interest in mathematics schoolwork by, first, proposing a theory of why such gender differences would arise and vary across countries, and second, testing several theoretical predictions in a large cross-national dataset. Results were consistent with both key components of the theory: high-achievement culture may be detrimental to interest in schoolwork and this effect may be amplified among girls due to their higher conformity to peer influence. These positive findings motivate further study of the validity and scope of the proposed mechanisms.

Data Availability Statement

Publicly available datasets were analyzed in this study. This data can be found here:

While posed vocalizations are perceived as positive for both low- and high-sum wins, real-life vocalizations are perceived as positive only for low-sum wins, but as negative for high-sum wins

Atias, D., & Aviezer, H. (2020). Real-life and posed vocalizations to lottery wins differ fundamentally in their perceived valence. Emotion Nov 2020.

Rolf Degen's take:

Abstract: A basic premise of classic emotion theories is that distinct emotional experiences yield distinct emotional vocalizations—each informative of its situational context. Furthermore, it is commonly assumed that emotional vocalizations become more distinct and diagnostic as their intensity increases. Critically, these theoretical assumptions largely rely on research utilizing posed vocal reactions of actors, which may be overly simplified and stereotypical. While recent work suggests that intense, real-life vocalizations may be nondiagnostic, the exact way in which increasing degrees of situational intensity affect the perceived valence of real-life versus posed expressions remains unknown. Here we compared real-life and posed vocalizations to winning increasing amounts of money in the lottery. Results show that while posed vocalizations are perceived as positive for both low- and high-sum wins, real-life vocalizations are perceived as positive only for low-sum wins, but as negative for high-sum wins. These findings demonstrate the potential gaps between real-life and posed expressions and highlight the role of situational intensity in driving perceptual ambiguity for real-life emotional expressions.

Baby brain: We found no evidence of overall cognitive decline in the pregnant group, and the IQ scores of pregnant women increased more than non-pregnant control participants across matched time intervals

Changes in intelligence across pregnancy and the postpartum period. M. D. Rutherford, Marla V. Anderson. Human Ethology, Volume 35, 91-105, November 21, 2020.

Rolf Degen's take:

Although the popular press describes pregnancy-related cognitive decrements, sometimes called “baby brain”, controlled studies have not consistently found reliable evidence of a decline in cognitive function during pregnancy. A functional approach measuring components of intelligence as they change across the trimesters of pregnancy and into the postpartum may help resolve this puzzle. The current study was a longitudinal study in which pregnant women and a control group took standardized IQ tests at 12-week intervals. We found no evidence of overall cognitive decline in the pregnant group, and the IQ scores of pregnant women increased more than non-pregnant control participants across matched time intervals. The increase in raw scores of fluid intelligence subscales was not statistically significant, nor was it significantly different than the increase in the control group.

Keywords: Pregnancy, Postpartum, Cognition, Intelligence.

Check also From Baby Brain to Mommy Brain: Widespread Gray Matter Gain After Giving Birth. Eileen Luders et al. Cortex, January 28 2020.

Heritability of general reading-related neurocognitive components (reading, letter-word knowledge, phonological decoding, reading comprehension, spelling, phonological awareness, & rapid automatized naming)

The heritability of reading and reading-related neurocognitive components: A multi-level meta-analysis. Chiara Andreola et al. Neuroscience & Biobehavioral Reviews, November 24 2020.


• Heritability estimates vary widely across reading-related neurocognitive skills.

• Age- and school grade-specific genetic influences have been reported.

• Past meta-analyses focused on some reading skills without controlling for moderators.

• Reading-related skills show moderate-to-substantial meta-heritability estimates.

• School grade levels moderated the heritability of some reading-related skills.


Reading ability is a complex task requiring the integration of multiple cognitive and perceptual systems supporting language, visual and orthographic processes, working memory, attention, motor movements, and higher-level comprehension and cognition. Estimates of genetic and environmental influences for some of these reading-related neurocognitive components vary across reports.

By using a multi-level meta-analysis approach, we synthesized the results of behavioral genetic research on reading-related neurocognitive components (i.e. general reading, letter-word knowledge, phonological decoding, reading comprehension, spelling, phonological awareness, rapid automatized naming, and language) of 49 twin studies spanning 4.1 to 18.5 years of age, with a total sample size of more than 38,000 individuals.

Except for language for which shared environment seems to play a more important role, the causal architecture across most of the reading-related neurocognitive components can be represented by the following equation a² > e² > c². Moderators analysis revealed that sex and spoken language did not affect the heritability of any reading-related skills; school grade levels moderated the heritability of general reading, reading comprehension and phonological awareness.

Keywords: meta-analysisreading-related skillstwin studyheritabilitygenetics

Women maximizing their visit to a nightclub: Marked increases in amounts of flesh exposed, heel heights of shoes, use of a wider range of makeup products & increases in the colour intensity of many of those products (lips and eyes)

Women’s strategic use of clothing and make-up. Colin Hendrie, Rhiannon Chapman, Charlotte Gill. Human Ethology, Volume 35, 16-26, March 9, 2020.

Abstract: Clothing and make-up signal a wide range of characteristics including age, sex and sexual motivation. The present study examined the change from daywear to clothing/make-up worn in preparation for a ‘night out’ that would include a visit to a nightclub in over one hundred young women living in the UK. Amounts of flesh exposed were derived from photographs of participants and intensity of make-up products used determined using the ‘Methuen handbook of colour’. Results showed marked increases in amounts of flesh exposed, heel heights of shoes, use of a wider range of makeup products and increases in the colour intensity of many of those products, particularly those used on the lips and eyes. It is concluded that the young women in this study prepared themselves for a ‘night out’ that would include a visit to a nightclub in ways designed to maximise the rich opportunities to attract the attention of potential sexual partners provided by such venues

Keywords: clothing, make-up, sexual signalling, women

When required to justify their evaluations, politicians rely more on prior political attitudes and less on policy information; they are more immune to the correction of biases than the public

Motivated reasoning and policy information: politicians are more resistant to debiasing interventions than the general public. Julian Christensen, Donald P Moynihan. Behavioural Public Policy, November 24 2020.

Rolf Degen's take:

Abstract: A growing body of evidence shows that politicians use motivated reasoning to fit evidence with prior beliefs. In this, they are not unlike other people. We use survey experiments to reaffirm prior work showing that politicians, like the public they represent, engage in motivated reasoning. However, we also show that politicians are more resistant to debiasing interventions than others. When required to justify their evaluations, politicians rely more on prior political attitudes and less on policy information, increasing the probability of erroneous decisions. The results raise the troubling implication that the specialized role of elected officials makes them more immune to the correction of biases, and in this way less representative of the voters they serve when they process policy information.

Discussion and exploratory analysis

The motivation to defend political attitudes is powerful, leading many to auto-accept politically congenial information while disregarding information that challenges existing views about the world. While lending some support to the potential to debias citizens, we find that politicians become more inclined to engage in politically motivated reasoning when required to justify their evaluations.

Why might politicians differ from citizens in their reactions to our experiment's justification requirement? While our study was not designed to offer causal evidence to answer this question, we can draw on our data to explore which possible explanations are more or less likely. One possibility is that personal characteristics, such as being more politically engaged (Taber & Lodge, Reference Taber and Lodge2006), make politicians more resistant towards debiasing interventions, meaning that the politician–citizen differences are due to self-selection. As a proxy for such personal characteristics, we can test the role of political interest, which was measured in the general public survey and is ‘a standard measure of psychological engagement in politics’ (Brady et al.Reference Brady, Verba and Schlozman1995). If the bias-strengthening effects of justification requirements among politicians are driven by self-selection based on political engagement, similar effects would be expected among the group of people who are most politically interested. However, this is not the case for our sample (see the regression analysis in Supplementary Material S4). The respondents who are most interested in politics, and who should therefore, according to the explanation above, be expected to react most like politicians, are the ones who drive the overall debiasing effect on non-politicians’ reasoning, meaning that they are the ones who behave least like politicians in reaction to justification requirements. Thus, our data suggest that explanations other than self-selection must be considered.

Another possibility is that the politician's role changes how people respond to justification requirements. Some studies show that professional roles lead certain groups to make unbiased professional judgments (Kahan, Reference Kahan2016b). For instance, relative to the public, judges and lawyers appear to be less biased when asked to evaluate judicial information, implying that legal training, but possibly also the demands of their job, condition legal professionals to better resist politically biased processing of information (Kahan et al.Reference Kahan, Hoffman, Evans, Devins, Lucci and Cheng2016). Like judges and lawyers, we may consider a politician to be a professional actor who is regularly asked to make judgments based on decision-relevant information. However, where a judicial professional is expected to set aside political attitudes and partisan identities, it is a politician's job to be a partisan (Andeweg, Reference Andeweg1997) and to avoid punishment from an external audience that values credible commitments (Tomz, Reference Tomz2007). As discussed in relation to H2 and H3, politicians are expected to be consistent in their political views and to defend the policy preferences upon which they have been elected. Politicians are trained to treat inconsistency as a sign of weakness, the trademark of a flip-flopper who will be penalized by voters and other political stakeholders (Tomz, Reference Tomz2007). Thus, their professional role gives politicians an incentive to treat justification requirements not as an opportunity to examine and nuance their own reasoning, but to construct arguments in favor of preselected conclusions.

While our experiments were not designed to test effects of role differences between politicians and the public, we can compare the responses of recently elected politicians with those of more experienced colleagues. If the bias-strengthening effect of justification requirements is due to politician-specific norms, we would expect the effect to be stronger among those who have been more exposed to those norms over time. Table 3 divides politicians between those elected in the previous year (39% of our sample) and the rest of our sample who had all been in office for 5 years or more. Consistent with the role-based explanation, Table 3 shows the bias-strengthening effect to be driven by experienced politicians. The justification requirement has no effect on the recently elected politicians in model 1, but has significant bias-strengthening effects on the experienced politicians in model 2.

Table 3. Recently elected versus experienced politicians (logistic regression analysis with standard errors in parentheses).

Note: Politicians are coded as ‘recently elected’ if the most recent election (in November 2013, 1 year before our data collection) was the first election where they were elected and ‘experienced’ if they were elected before the 2013 election. The dependent variable measures whether respondents identify the supplier with the highest satisfaction rate as being the one that performs the best.

p < 0.1, *p < 0.05, **p < 0.01, ***p < 0.001; two-sided significance tests.

To cast further light on the reasoning strategies of our respondents, we coded the qualitative content of the written justifications (for the coding scheme and analyses, see Supplementary Material S6). The results of our qualitative content analyses provide additional evidence of our results being driven by experienced politicians having learned strategies to confront attitude-uncongenial information as an expert motivated reasoner. Thus, whereas the qualitative content of the justifications provided by non-politicians and recently elected politicians was more or less unaffected by the attitude-congeniality of the experiments’ information, experienced politicians more often adapted their arguments depending on the information at hand. Specifically, as reported in the supplementary material's Tables S6ca and S6cb, the experienced politicians tended to base their justifications on the tables’ data (i.e., they referred to parent satisfaction) when this was attitude-congenial. However, Table S6ce shows that when the data were uncongenial, the experienced politicians more often based their justifications on specific conditions of local government (this could be equity considerations, expectations regarding the education of staff, etc.). Because these are explorative analyses of data, which were not collected for the purpose of testing the effects of roles, caution is needed when evaluating the results. However, the results are consistent with the idea that, over time, through their job, politicians learn how to defend their attitudes and beliefs ‘like a politician’ when faced with attitude-uncongenial information.

Cannabis: 70–85% of users reported increased sexual pleasure/satisfaction, 25–40% prolonged duration of intercourse, 55–70% heightened sensation; & reported more coital frequency; but placebo effect cannot be ruled out

Cannabinoid signalling and effects of cannabis on the male reproductive system. Mauro Maccarrone, Cinzia Rapino, Felice Francavilla & Arcangelo Barbonetti. Nature Reviews Urology, November 19 2020.

Rolf Degen's take:

Key points

* Marijuana has the highest consumption rate of any recreational drug in the Western world.

* Endocannabinoids and their receptors, enzymes and transporters, which together form the endocannabinoid system (ECS), are present in various components of the male reproductive tract, including male genital glands, testis and sperm.

* Preclinical studies have shown that the ECS is involved in negative modulation of testosterone secretion by acting at both central and testicular levels.

* As yet, clinical data are insufficient to conclude that cannabinoids have a harmful effect on human male sexual function and fertility.

* Although cannabinoid receptors are present in the testes and sperm, the effects of cannabinoid exposure on spermatogenesis largely remain to be clarified.

* The ECS has the potential to provide new drug targets in male reproductive disorders, and its components might be useful as biomarkers of male infertility.

Abstract: Marijuana is the most widely consumed recreational drug worldwide, which raises concerns for its potential effects on fertility. Many aspects of human male reproduction can be modulated by cannabis-derived extracts (cannabinoids) and their endogenous counterparts, known as endocannabinoids (eCBs). These latter molecules act as critical signals in a variety of physiological processes through receptors, enzymes and transporters collectively termed the endocannabinoid system (ECS). Increasing evidence suggests a role for eCBs, as well as cannabinoids, in various aspects of male sexual and reproductive health. Although preclinical studies have clearly shown that ECS is involved in negative modulation of testosterone secretion by acting both at central and testicular levels in animal models, the effect of in vivo exposure to cannabinoids on spermatogenesis remains a matter of debate. Furthermore, inconclusive clinical evidence does not seem to support the notion that plant-derived cannabinoids have harmful effects on human sexual and reproductive health. An improved understanding of the complex crosstalk between cannabinoids and eCBs is required before targeting of ECS for modulation of human fertility becomes a reality.


Despite data suggesting that cannabis use can affect human sexual function, its effects remain under debate, as favourable effects on sexual behaviour and motivational, hedonic and/or perceptual aspects of sexual intercourse have been also reported. Some studies77have suggested that 70–85% of marijuana consumers experience increased sexual pleasure and satisfaction, 25–40% prolonged duration of intercourse, and 55–70% heightened orgasmic sensation78,79. Furthermore, the National Survey of Family Growth (NSFG), a representative cross- sectional survey on a well- controlled cohort of almost 23,000 men in the USA, showed that increased frequency of marijuana use was associated with increased coital frequency, even after adjustment for demographic, socio- economic and anthropometric variables80(Table 3). Notably, these data are all self-reported and, therefore, are at risk of both recall bias and exaggeration by participants; thus, they should be interpreted with caution. The authors hypothesized that individuals who engage in marijuana use might be more psychologically disinhibited than those who do not, which could be reflected in their sex life as high coital frequency80. Furthermore, although sexual pleasure could be at least partially attributed to an actual enhancement of sensory experience, especially in terms of an increased sensitivity to touch, which has been reported in cannabis users78, a placebo effect cannot be ruled out, given the anecdotal reputation of cannabis as an aphrodisiac77. These aspects should be taken into account when interpreting the increased sexual pleasure and satisfaction among marijuana consumers reported in previous studies77.