Monday, November 28, 2022

Gender differences in cooperation across 20 societies: Overall, our findings revealed little-to-no evidence for an association between gender and cooperation

Gender differences in cooperation across 20 societies: a meta-analysis. Giuliana Spadaro, Shuxian Jin and Daniel Balliet. Philosophical Transactions of the Royal Society B: Biological Sciences. November 28 2022.

Abstract: Past research hypothesized that men and women differ in their tendency to cooperate with strangers in situations that involve a conflict of interests. However, recent empirical research has provided converging evidence that men and women cooperate to a similar extent, and that differences in cooperation can emerge in response to specific situational and societal contexts. Here we analyse six decades of empirical research on human cooperation using social dilemmas (1961–2017, k = 126) conducted across 20 industrialized societies, testing pre-registered hypotheses derived from evolutionary theory and social role theory. Overall, our findings revealed little-to-no evidence for an association between gender and cooperation using different meta-analytic approaches. We did not find within-study differences in cooperation between men and women (d = 0.011, 95% CI [−0.038, 0.060]). However, cooperation was slightly higher across studies with predominantly female samples (k = 972). In addition, contrary to our predictions, gender differences in cooperation did not emerge in response to the degree of conflicting interests in the situation, and societal levels of gender equality and economic development. We discuss the implications of these findings for our understanding of gender differences in cooperation.

4. Discussion

This meta-analysis examined empirical studies on cooperation using social dilemma paradigms to answer questions about the relationship between participants' gender and cooperative behaviour. Specifically, we tested whether women are overall more cooperative than men, and novel pre-registered hypotheses about the moderating role of contextual factors such as the degree of conflict in the situation, and societal adherence to canonical gender roles and economic development. Overall, we found little-to-no evidence for gender differences in cooperation and no support for the additional moderation hypotheses. Below, we discuss these findings, their limitations, and suggest some potential directions for future research.

In line with previous meta-analytic evidence [12], we found no within-study differences in cooperation between men and women. Men and women displayed comparable levels of cooperation in Prisoner's Dilemmas, public goods dilemmas and resource dilemma games (k = 126, d = 0.011). However, we did find a significant association between overall gender composition of the sample and the mean levels of cooperation across 972 studies. This result suggests that there is higher cooperation in studies with a higher prevalence of women. Although this latter analysis benefits from a large number of studies, societies, and experimental settings, we should interpret these findings with caution based on (a) potential methodological confounds related to changes in samples over time, and (b) conflict with existing evidence. In fact, over the last 60 years, cooperation in studies using economic games has increased over time [46], and so did the inclusion of women in the experimental samples [47]. In our data, year of data collection is both positively correlated with logit-transformed cooperation rates (r = 0.17, p < 0.001) and negatively associated with proportion of men in the sample (r = −0.27, p < 0.001). Although the association of gender composition of the sample and cooperation remains significant while controlling for year of data collection (b = −0.286, p = 0.002), we could not rule out that temporal trends in methodologies could account for the observed significant association. In addition, this analysis does not replicate the result of a similar analysis using a broader set of studies (N = 1527) and that controls for a greater number of study characteristics (e.g. mean age of the sample, discipline of study, symmetry, deception) [19]. Considering these concerns, we conclude that we do not find compelling evidence in support of gender differences in cooperation.

We further tested whether women cooperate more than men in situations involving greater conflict of interests. The findings did not provide support for this prediction, either examining whether the degree of conflict (i) moderated within-studies gender differences in cooperation or (ii) interacted with gender composition of the sample to predict mean levels of cooperation across studies. Given that situations with higher conflict of interests involve more risk of exploitation, these null findings can also inform research investigating whether gender differences in cooperation relate to gender-specific attitudes toward risks [5,34,48]. The severity of conflict in the meta-analysis was operationalized using the payoff structure (i.e. the K index, [32]) of games that afford the potential for exploitation [30]. Although this approach had the advantage of evaluating the moderation of conflict within situations that had a similar incentive structure, the studies included in the meta-analysis presented little variation in the K index. In fact, the K index ranged from 0.20 to 0.40 for 46% of the studies (M = 0.46, Mdn = 0.40, s.d. = 0.21). Although this is in line with what is observed across all studies in CoDa (e.g. 39% ranging between 0.20 and 0.40, [49]), variation within the K index might be too small to detect any differential responses to stress or emergence of canonical gender roles to result in gender differences in cooperative responses. An alternative way to test this hypothesis could be to examine gender differences in cooperative behaviour across game situations with weak or strong exploitation components (e.g. as done in [31] by comparing behaviour in a ultimatum game and a Prisoner's Dilemma). In addition, the type of conflict of interests faced in situations resembling a Prisoner's Dilemma structure might only be a small fraction of the situations experienced in daily life [50], and Prisoner's Dilemma situations might provide situational cues of the potential of exploitation that could affect the occurrence of gender-typical behaviour [27]. A promising avenue for future research might be then to examine cooperative behaviour by systematically varying other relevant situational features, such as introducing the possibility to benefit others through one's competitive behaviour (e.g. socially oriented incentives, [51]) and the information about the interaction partner (e.g. anonymity, [5]). The identification of additional contextual features can contribute to a more comprehensive understanding of the mixed patterns of findings on gender differences in cooperation.

In addition, in the present meta-analysis, gender differences in cooperation did not vary across societies. This evidence is in line with studies showing little evidence for cross-cultural variation of gender differences in prosocial behaviour in children from both industrialized and small-scale societies [52]. Here, studies conducted in societies at different levels of gender equality and economic development displayed very similar cooperation by men and women. Although differences would be expected in light of social role theory [13,27], these findings are in line with recent empirical evidence showing that gender inequality was not associated with differences in magnitude of gender differences in cooperative behaviour in a Prisoner's Dilemma in 10 countries [5]. Compared to Dorrough & Glöckner's study [5], our meta-analysis included a broader range of countries and societal indicators, such as ratio of female to male labour force participation rates [39] and the number of years since women's suffrage [40]. However, none of these seven indicators was significantly correlated to mean differences in cooperation across studies (p-values ≥ 0.292). These findings are consistent with recent meta-analytic work showing no evidence for cross-cultural variation in cooperation more broadly [53]. It is worth mentioning, however, that despite our effort to obtain more studies (e.g. through direct requests to authors), findings from more recent cross-cultural studies detecting gender differences in cooperation could not be included, since these studies were not yet annotated in CoDa (e.g. [4,5]). As such, our meta-analysis has low statistical power to detect variation across societies, due to the limited number of effects available for each society. Moreover, the included studies mostly comprised WEIRD samples [54] and might not be representative of the actual cross-cultural variation in cooperative behaviour. For a more comprehensive analysis, we encourage future work to more systematically disclose information about cooperation displayed by men and women, or to provide this information retrospectively for previously published studies (e.g. through CoDa [35]). At present, however, these limitations might impact the reliability of variance observed at the highest level of the model. More research is needed to replicate our findings with a broader set of societies and observations.

Last, we tested whether other features of the interaction context moderated gender differences in cooperation to provide a conceptual replication of findings from previous meta-analytic work [12]. We did replicate that gender is not associated with cooperation and that group size and year of data collection do not significantly moderate the gender effects after controlling for several study characteristics. However, we found no support for the moderation hypotheses related to gender composition of the group, group size, iterations, and year of data collection, as none of these variables were significantly associated with the magnitude of gender differences in cooperation. These different patterns of findings might be due to the way primary studies have been selected in the present work, namely the inclusion of more recent studies (2010–2017, k = 37), and the adoption of stricter inclusion criteria (e.g. matrix games not classifiable as Prisoner's Dilemma and public goods games were not included, and so did studies involving interactions among acquaintances). It is worth noting that our goal was not to perform an exact replication of previous work. Nevertheless, the conceptual replication of the main effect provides even stronger evidence that there is no main overall association between gender and cooperation. Furthermore, the lack of moderation of the association between gender and cooperation suggests that these moderation effects are not very robust to variations in the data selection and analytic techniques—and so should be interpreted with caution. The fact that the moderating effects were not robust to these adjustments suggest that even small variations of the context can be crucial to elicit (or not) gender differences in cooperation. For example, the present meta-analysis included additional studies from more recent years, and there have been changes in samples and methods in the literature over time, such as more recent studies having (a) a greater percentage of women, (b) fewer student samples, and (c) a stronger conflict of interests (i.e. lower K value) [47]. Future studies might consider to experimentally manipulate the situational features of interest, such as gender composition of the group (e.g. [55]) and conflict of interests (e.g. [56]), to provide a further test of these moderating hypotheses.

Analysis of 48 countries in the 2000–2018 PISA tests: Mainly positive Flynn effects in economically less developed countries, negative Flynn effects in the economically most advanced countries

Ongoing trends of human intelligence. Gerhard Meisenberg, Richard Lynn. Intelligence, Volume 96, January–February 2023, 101708.

Abstract: The aim of the study is to estimate the most recent trends of intelligence world-wide. We find that the most recent studies report mainly positive Flynn effects in economically less developed countries, but trivial and frequently negative Flynn effects in the economically most advanced countries. This is confirmed by an analysis of 48 countries in the 2000–2018 PISA tests, showing that high pre-existing IQ and school achievement are the best predictors of declining test scores. IQ gaps between countries are still large (e.g., 19 IQ points in PISA between East Asia and South Asia) but are diminishing world-wide. We predict that these trends, observed in adolescents today, will reduce cognitive gaps between the working-age populations of countries and world regions during coming decades. As is predicted by the well-established relationship between intelligence and economic growth, there is already evidence that the ongoing cognitive convergence is paralleled by global economic convergence. These developments raise questions as to how long this cognitive and economic convergence will continue, whether it will eliminate cognitive and economic gaps between countries entirely, and whether a condition with high levels of cognitive ability and economic prosperity is sustainable long-term.


The last century has seen two developments in intelligence research that are sufficiently profound to be called “scientific revolutions” (Kuhn, 1962): the importance of genetics for individual differences, and the discovery that intelligence changes on the historical time scale, with major rises of intelligence having taken place during the 20th century. Jim Flynn's work was at the center of the second of these scientific revolutions. Scattered reports about rising intelligence had appeared since the 1930s (Lynn, 2013), but the pervasive nature of secular intelligence gains was not recognized until Flynn's work during the 1980s, when he showed rising IQ in the United States and world-wide (Flynn, 1984, Flynn, 1987).

Flynn did not fully grasp the significance of his findings at once. In his 1987 paper (p. 187), he concluded: “The Ravens Progressive Matrices Test does not measure intelligence but rather a correlate with a weak causal link to intelligence; the same may apply to all IQ tests.” Elsewhere he asks: “Why aren't we undergoing a renaissance unparalleled in human history? …why aren't we duplicating the golden days of Athens or the Italian Renaissance?” (Holloway, 1999). At that time, Flynn did not believe that “real” intelligence could have risen so much. Only later did he fully acknowledge the reality and importance of rising intelligence, for the functioning of a modern economy and even for the moral progress he saw during the 20th century (Flynn, 2013, Flynn, 2014).

Two major meta-analyses have confirmed the ubiquity of test score gains (Pietschnig & Voracek, 2015; Trahan, Stuebing, Fletcher, & Hiscock, 2014). We also know that the Flynn effect is not strongest on the most g-loaded tests (te Nijenhuis, 2013; te Nijenhuis & Van Der Flier, 2013). This suggests that the causal factors that determine individual differences in intelligence, and thereby the correlations between its cognitive components, are different from the factors that have changed the intelligence levels of entire populations over time. It has been claimed that, with proper controls included, the Flynn effect has been stronger on tests requiring more “abstract” thinking (Armstrong et al., 2016; Must, Must, & Mikk, 2016). More generally, gains on fluid intelligence have been stronger than gains on crystallized intelligence, at least in most of the times and places for which we have informative data. Some abilities included in the g nexus did not show any evidence of Flynn effects, including reaction time (e.g., Nettelbeck & Wilson, 2004), digit span (Gignac, 2015; Woodley of Menie & Fernandes, 2015), and ability-based emotional intelligence (Pietschnig & Gittler, 2017).

There is general agreement that the Flynn effect, and perhaps also its reversal in some countries, is caused by environmental changes rather than genetics (Bratsberg & Rogeberg, 2018). Schooling is a likely candidate considering that the educational level of the population has risen massively over time (Schofer & Meyer, 2005) and that each year of additional school attendance during adolescence raises the IQ by 1–5 points (Ritchie & Tucker-Drob, 2018); and like the Flynn effect, schooling gains are not on g, but on specialized cognitive skills (Ritchie, Bates, & Deary, 2015). Improved nutrition is another likely contributor to Flynn effects (Lynn, 1990).

Intelligence is important for human societies. Weede and Kämpf (2002) were the first to present evidence that the rate of economic growth is predicted mainly by two variables: initial per capita GDP, and average intelligence of the population. Low initial per capita GDP and high intelligence is the combination that favors rapid economic growth. This key finding has been confirmed in multiple further studies (e.g., Francis & Kirkegaard, 2022; Jones & Schneider, 2006; Meisenberg, 2012, Meisenberg, 2014a). It implies that in the short term, countries gravitate towards a level of prosperity that is commensurate with their level of intelligence. On longer time scales, this observation predicts that countries with rising intelligence become richer while those with declining intelligence become poorer.

Combining these findings with the earlier conclusion that the Flynn effect is caused by environmental improvements associated with economic development, such as high-intensity educational systems and the elimination of childhood malnutrition, we can conclude that since the industrial revolution, economic development and the Flynn effect have reinforced each other in an upward spiral, a positive feedback that has created modern industrial society (Meisenberg, 2014a, Meisenberg, 2014b). It implies that the maintenance of high intelligence is a requirement for the maintenance of well-functioning and prosperous societies. It is this theory which motivates our investigations into the current and projected future trajectories of human intelligence in the countries of the world. The importance of this research is underscored by recent reports about the end of the Flynn effect, and even its reversal, especially in several European countries (Dutton, van der Linden, & Lynn, 2016). In the present study, we investigate which countries of the world still have positive Flynn effects, and where intelligence is stagnating or declining.