Sex Differences in General Knowledge: Meta-Analysis and New Data on the Contribution of School-Related Moderators among High-School Students Ulrich S. Tran*, Agnes A. Hofer, Martin Voracek Department of Basic Psychological Research and Research Methods, School of Psychology, University of Vienna, Vienna, Austria Abstract Research from various countries consistently reported an advantage of boys over girls in general knowledge and was also suggestive of some overall trends regarding specific domains of general knowledge that were speculated to stem from biologically differentiated interests. However, results were heterogeneous and, as of yet, had not been evaluated meta- analytically. Moreover, previous research drew on overly homogeneous high-school or undergraduate samples whose representativeness appears problematic; mostly, likely moderators, such as school type, student age or parental education, were also not directly investigated or controlled for. We provide a meta-analytical aggregation of available results regarding sex differences in general knowledge and present new data, investigating the psychometric properties of the General Knowledge Test (GKT), on which previous research primarily relied, and explored sex differences in a large and heterogeneous Austrian high-school student sample (N = 1088). The aggregated sex effect in general knowledge was of medium size in previous research, but differences in specific domains were heterogeneous across countries and only modest at best. Large sex differences in our data could be explained to a large part by school-related moderators (school type, school, student age, parental education) and selection processes. Boys had a remaining advantage over girls that was only small in size and that was consistent with the magnitude of sex differences in general intelligence. Analysis of the GKT yielded no evidence of biologically differentiated interests, but of a specific interest in the humanities among girls. In conclusion, previous research likely overestimated sex differences in general knowledge. Citation: Tran US, Hofer AA, Voracek M (2014) Sex Differences in General Knowledge: Meta-Analysis and New Data on the Contribution of School-Related Moderators among High-School Students. PLoS ONE 9(10): e110391. doi:10.1371/journal.pone.0110391 Editor: Keith Laws, University of Hertfordshire, United Kingdom Received July 1, 2014; Accepted September 4, 2014; Published October 27, 2014 Copyright: ß 2014 Tran et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All data relevant to the meta-analysis are within the paper. The data file on the Austrian high-school student data is available from Figshare at: http://dx.doi.org/10.6084/m9.figshare.1170016. Funding: The authors have no support or funding to report. Competing Interests: The authors hereby confirm that coauthor Martin Voracek is a PLOS ONE Editorial Board member. This does not alter the authors’ adherence to PLOS ONE editorial policies and criteria. * Email: ulrich.tran@univie.ac.at Introduction Sex differences in cognitive abilities and intelligence are a much investigated topic, with a host of studies documenting an advantage of women in verbal tasks and perceptual speed, but an advantage of men in visuospatial and complex numerical abilities [1]. Moreover, evidence points towards an advantage of men over women in fluid intelligence (Gf) [2–4], but also in crystallized intelligence (Gc) and general knowledge [5,6]. Evidence from the standardization samples of information subtests of the Wechsler intelligence tests since 1958 consistently points towards an advantage of men in general knowledge [6,7]. Yet, research points out that general knowledge is an intellectual ability sui generis (‘semantic long-term memory’) that possibly needs to be regarded as another factor besides Gc and Gf, instead of being conceptualized as a verbal factor of Gc, and that may not be sufficiently explained by verbal ability, general intelligence, Gc or Gf alone [8–11]. Newer studies assessed general knowledge with a specific instrument, the General Knowledge Test (GKT) [9]. The original GKT consists of 216 items with an open response format that cover 19 different domains of knowledge. Its questions encompass ‘‘culturally valued knowledge, communicated by a range of non- specialist media’’ ([9], p. 859), like Who discovered the double helix structure of DNA? or Which is the longest river in Asia?, that are scored correct/incorrect, assigning half points to partly correct answers in some items. Irwing et al. [9] provided evidence that the 19 domains conform to a hierarchical second-order factor model, wherein six first-order factors (Current Affairs, Fashion, Family, Physical Health, Arts, and Science) load on the second-order factor general knowledge and account for the interrelations between the lower-order domains. Short forms, translations, and variants of the GKT were used in a number of further studies [10,12–18]. A number of studies with the GKT addressed sex differences explicitly and provided converging evidence on sizable sex differences in general knowledge, and sometimes also with regard to underlying domains. There seems to be a specific male advantage in domains that are concerned with competition for status and power (Current Affairs, Physical Health), and a female advantage in domains that are concerned with nurturance and family (Family). This pattern was interpreted by some authors as suggestive of biological, i.e., evolutionarily developed and PLOS ONE | www.plosone.org 1 October 2014 | Volume 9 | Issue 10 | e110391