How diverse are the samples used in the journals 'Evolution & Human Behavior' and 'Evolutionary Psychology'?

Psychologists regularly draw inferences about populations based on data from small samples of people, and so have long been interested in how well those samples generalise to wider populations. There is a consensus that psychology probably relies too much on samples from Western Educated Industrialised Rich and Democratic (WEIRD) societies, and among those from university students. Online surveys might be used to increase sample diversity, although online sampling still reaches only a restricted range of participants. Studies from evolutionary psychology often seek to uncover aspects of evolved universal characteristics, and so might demonstrate a particular interest in the use of diverse samples. Here, we empirically examine the samples used in the 2015-2016 volumes of ‘Evolution & Human Behavior’ (104 articles) and ‘Evolutionary Psychology’ (76 articles). Our database consists of 311 samples of humans (median sample size = 186). The majority of samples were either online or student samples (70% of samples), followed by other adult Western samples (19%). 253 (81%) of the samples were classified as ‘Western’ (Europe/North America/Australia). The remaining samples were predominantly from Asia (N= 37; 12%, mostly Japan). Only a small fraction of the samples was taken from Latin American and Caribbean (N = 8) or African (N = 6) countries. The median sample size did not differ significantly between continents, but online samples (both paid and unpaid) were typically larger than samples sourced offline. It seems that the samples used are more diverse than those that have been reported in reviews of the literature from social and developmental psychology, perhaps because evolutionary psychology has a greater inherent need to test hypotheses about an evolved and universal human nature. However, it is also apparent that the majority of samples within contemporary evolutionary psychology research remain WEIRD.