Converging evidence for greater male variability in time, risk, and social preferences.

Gender differences in time, risk, and social preferences are important determinants of differential choices of men and women, with broad implications for gender-specific social and economic outcomes. To better understand the shape and form of gender differences in preferences, researchers have traditionally examined the mean differences between the two genders. We present an alternative perspective of greater male variability in preferences. In a meta-analysis of experimental economics studies with more than 50,000 individuals in 97 samples, we find converging evidence for greater male variability in time, risk, and social preferences. In some cases, we find greater male variability in addition to mean differences; in some cases, we only find greater male variability. Our findings suggest that theories of gender differences are incomplete if they fail to consider how the complex interaction of between-gender differences and within-gender variability determines differential choices and outcomes between women and men.

Greater Male Variability in Cooperation: Meta-Analytic Evidence for an Evolutionary Perspective.

Do men and women differ systematically in their cooperation behaviors? Researchers have long grappled with this question, and studies have returned equivocal results. We developed an evolutionary perspective according to which men are characterized by greater intrasex variability in cooperation as a result of sex-differentiated psychological adaptations. We tested our hypothesis in two meta-analyses. The first involved the raw data of 40 samples from 23 social-dilemma studies with 8,123 participants. Findings provided strong support for our perspective. Whereas we found that the two sexes do not differ in average cooperation levels, men are much more likely to behave either selfishly or altruistically, whereas women are more likely to be moderately cooperative. We confirmed our findings in a second meta-analytic study of 28 samples from 23 studies of organizational citizenship behavior with 13,985 participants. Our results highlight the importance of taking intrasex variability into consideration when studying sex differences in cooperation and suggest important future research directions.

Surface acoustic wave mediated carrier injection into individual quantum post nano emitters.

Acousto-electric charge conveyance induced by a surface acoustic wave (SAW) is employed to dissociate photogenerated excitons. Over macroscopic distances, both electrons and holes are injected sequentially into a remotely positioned, isolated and high quality quantum emitter, a self-assembled quantum post. This process is found to be highly efficient and to exhibit improved stability at high acoustic powers when compared to direct optical pumping at the position of the quantum post. These characteristics are attributed to the wide matrix quantum well in which charge conveyance occurs and to the larger number of carriers available for injection in the remote configuration, respectively. The emission of such pumped quantum posts is dominated by recombination of neutral excitons and fully directional when the propagation direction of the SAW and the position of the quantum post are reversed.

Enhanced sequential carrier capture into individual quantum dots and quantum posts controlled by surface acoustic waves.

Individual self-assembled quantum dots and quantum posts are studied under the influence of a surface acoustic wave. In optical experiments we observe an acoustically induced switching of the occupancy of the nanostructures along with an overall increase of the emission intensity. For quantum posts, switching occurs continuously from predominantly charged excitons (dissimilar number of electrons and holes) to neutral excitons (same number of electrons and holes) and is independent of whether the surface acoustic wave amplitude is increased or decreased. For quantum dots, switching is nonmonotonic and shows a pronounced hysteresis on the amplitude sweep direction. Moreover, emission of positively charged and neutral excitons is observed at high surface acoustic wave amplitudes. These findings are explained by carrier trapping and localization in the thin and disordered two-dimensional wetting layer on top of which quantum dots nucleate. This limitation can be overcome for quantum posts where acoustically induced charge transport is highly efficient in a wide lateral matrix-quantum well.