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. https://doi.org/10.1098/rstb.2021.0438

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.