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Sex differences in human performance have been documented across a wide array of human endeavours. Males tend to exhibit higher performance in intellectually demanding and competitive domains, and this difference tends to be more pronounced the higher the level of performance. Here, we analyse publishing performance for the whole population of associate and full professors in relatively sex-balanced disciplines, namely Education, Nursing and Caring Science, Psychology, Public Health, Sociology, and Social Work, comprising 426 women and 562 men. We find that sex differences in the number of publications, citations, and citations per publication were small across low and medium levels of productivity, but become more pronounced the higher the level of performance. In the top performing 10% the female proportion decreases from the average 43.2% to 26% (25 F, 71 M), which further decreases to 15% in the top 5%. The results are discussed with respect to the greater male variability hypothesis, sex differences in psychological traits, and environmental factors such as sex discrimination.

The proportion of women tends to decrease the higher the academic rank, following a global pattern. Sweden has taken comprehensive measures to decrease this gap across 30 years, and many countries are following a similar path. Yet today only 27% of faculty with the rank of professor in Sweden are female. A common explanation is that academia is biased against women. According to this hypothesis, women have to reach higher levels of scholarly achievement than men to be appointed to the same academic rank. Publication metrics when attaining the rank of professor were compiled from the Web of Science for samples of the whole population of 1345 professors appointed at the six largest universities in Sweden during a six-year period. Men had significantly more publications and citations in both medicine and in the social sciences, rejecting the hypothesis that women are held to a higher scholarly standard in this context.

Previous research has attempted to understand why countries with relatively favorable conditions and high estimated average IQs (such as Finland and Japan) have a relatively low per capita number of scientific Nobel prizes. In the present study, we examine whether there is a relationship between national schizophrenia and left-handedness prevalence, on the one hand, and per capita scientific and literary achievement, on the other hand, in countries with IQ estimates of at least 90. We found that per capita science and literature Nobel prizes and scientific publications are strongly negatively associated with schizophrenia and strongly positively correlated with left-handedness. There also was a very pronounced negative correlation between schizophrenia rate and left-handedness rate. These results suggest that genius can be regarded as a combination of very high IQ, aspects of high-functioning autism (specifically low empathy) plus relatively low impulse control, consistent with observations of intellectually outstanding individuals, and the fact that schizophrenia appears to constitute the opposite pole of these aspects of autism spectrum. We posit differences in androgen levels as a possible underlying explanation for these findings.

There are national differences in scientific activity that are not well accounted for by economic and intellectual factors alone. We examine the novel hypothesis that androgen levels may also play a role. Androgens are often referred to as male hormones, but are present in both men and women, and have been linked to performance in other domains, such as sports and entrepreneurship. National-level empirical data on scientific productivity, in terms of numbers of publications, and science Nobel laureates were compared to seven national-level androgen indicators; namely androgenic body hair, the length of the CAG repeat on the androgen receptor gene, prostate cancer incidence, male and female 2D:4D finger ratio, and sex frequency and number of partners. The majority of these indicators were associated in the expected direction with per capita number of scientific publications and Nobel prizes. Moreover, several indicators significantly interacted with national-level estimates of intelligence, such that androgen levels are related to measures of the scientific achievement only when the level of intelligence is relatively high. These findings may partly explain the global distribution of scientific productivity, achievements, and Nobel prizes.

The idea of far transfer effects in the cognitive sciences has received much attention in recent years. One domain where far transfer effects have frequently been reported is music education, with the prevailing idea that music practice entails an increase in cognitive ability (IQ). While cross-sectional studies consistently find significant associations between music practice and IQ, randomized controlled trials, however, report mixed results. An alternative to the hypothesis of cognitive transfer effects is that some underlying factors, such as shared genes, influence practice behaviour and IQ causing associations on the phenotypic level. Here we explored the hypothesis of far transfer within the framework of music practice. A co-twin control design combined with classical twin-modelling based on a sample of more than 10,500 twins was used to explore causal associations between music practice and IQ as well as underlying genetic and environmental influences. As expected, phenotypic associations were moderate (r = 0.11 and r = 0.10 for males and females, respectively). However, the relationship disappeared when controlling for genetic and shared environmental influences using the co-twin control method, indicating that a highly practiced twin did not have higher IQ than the untrained co-twin. In line with that finding, the relationship between practice and IQ was mostly due to shared genetic influences. Findings strongly suggest that associations between music practice and IQ in the general population are non-causal in nature. The implications of the present findings for research on plasticity, modularity, and transfer are discussed.