Does recent experience affect large male advantage in a sequentially-mating fish?

In many mating systems, large male body size is associated with dominance in direct contests with rivals and females may exhibit preference for larger males. As such, body size is often positively associated with mating success. However, mating experience can influence the potential advantage of large body size through alterations in behaviour and depletion of sperm reserves. In Japanese medaka (Oryzias latipes), males mate with many females each day, and larger males mate more frequently than smaller males. In an observational experiment, we tested the following alternate predictions: (1) recent mating experience may enhance mating success through a carry-over effect of prior mating, whereby small experienced males gain an advantage over large inexperienced rivals in mating contests; or (2) recent mating experience decreases mating success through a reduction in fertilization due to sperm limitation, effectively dampening the large-male advantage against a small inexperienced rival. We examined the interactive effect of size and recent experience on mating behaviour and success. While mating contests were monopolized by large males, recent experience enhanced mating success, especially in small male winners. Experienced males courted more readily than those without recent experience, suggesting that recent prior mating enhances this behaviour. Furthermore, males who had copulated recently did not exhibit sperm depletion when in the presence of a competitor, nor did female behaviour indicate a preference for inexperienced males. This suggests that males can use sexual experience to increase their reproductive success in future mating situations, which may influence the action of sexual selection and alternative tactics in shaping mating systems.

Sex Differences in 32,347 Jordanian 4th Graders on the National Exam of Mathematics

Sex differences in mathematical ability were examined in a nation-wide sample of 32,346 Jordanian 4th graders (age 9–10 year) on a 40-item mathematics test. Overall, boys were found to perform slightly worse ( d = −0.12) but had slightly more variation in scores ( SD = 1.02 and SD = 0.98 for boys and girls, respectively). However, when results were disaggregated by school type, single-sex versus coed (i.e., coeducational), boys were found to perform better than girls in coed schools ( d = 0.27) but worse across single-sex schools ( d = −0.37). Two-parameter item response theory analysis showed that item difficulty was similar across sexes in the full sample. Item loadings exhibited substantial departure from measurement invariance with respect to boys and girls at single-sex schools, though. For boys and girls at coed schools, both the item difficulty and item loading correlations were highly similar, evincing that measurement invariance largely held in this case. Partially consistent with findings from other countries, a correlation between item difficulty and male advantage was observed, r = .57, such that the relative male advantage increased with increased item difficulty. Complicating interpretation, this association did not replicate within coed schools. Item content, Bloom’s cognitive taxonomy category, and item position showed no relation to sex differences.

More Similar than Different: Gender Differences in Basic Numeracy are the Exception not the Rule

This study investigates gender differences in children on the basic numerical skills that are predictive of math achievement. Previous research in this area is inconsistent and has relied upon traditional hypothesis testing, which does not allow for assertive conclusions to be made regarding non-significant findings. This study is the first to compare male and female performance (N =1391; ages 6-13) on many basic numerical tasks using both Bayesian and frequentist analyses. The results provide strong evidence of gender similarities on the majority of basic numerical tasks measured, suggesting that a male advantage in foundational numerical skills is the exception rather than the rule.

Sex differences in 32,347 Jordanian 4th graders on the national exam of mathematics

Sex differences in mathematical ability were examined in a nation-wide sample of 32,346 Jordanian 4th graders (age 9-10) on a 40-item mathematics test. Overall, girls were found to perform slightly better (d = 0.12), while boys had slightly more variation in scores (standard deviations of 1.02 and 0.98 for boys and girls, respectively).2 parameter item response theory analysis showed that the item parameters were almost identical across sexes; correlations were .97 [95% confidence interval: .95 to .99] and .90 [.82 to .95] for difficulties and loadings, respectively. A bootstrapping analysis revealed that these could not be explained by sampling error alone, but reflected genuine departures from measurement invariance. However, sex differences in items showed no relationship to the relative size of the departure from measurement invariance.A correlation between item difficulty and male advantage was observed, r = .57 [.32 to .75] (.68 after exclusion of an outlier), such that the relative male advantage increased with increased item difficulty.Results were interpreted to be congruent with Richard Lynn’s developmental theory of sex differences in general intelligence.

Spatial Visualization Ability Mediates the Male Advantage in Spatial and Visual Episodic Memory

Individuals between the ages of 18 and 94 (N = 326) completed a battery of episodic memory tasks, as well as several measures of spatial visualization. A female advantage in verbal episodic memory and a male advantage in spatial and visual episodic memory were observed. Mediation analyses provided evidence that performance on spatial visualization tasks greatly influences the magnitude of the effect for sex differences among the different episodic memory constructs. In particular, the spatial visualization construct fully mediated the relationship between sex and episodic spatial memory performance. Further, when spatial visualization was included as a mediator in the model the relationship between sex and episodic verbal memory increased, and the relationship between sex and episodic visual memory reversed, such that women scored higher than men.