The sexes do not differ in general intelligence, but they do in some specifics
Introduction
The study of sex differences in psychological variables dates back over 100 years (Hedges & Nowell, 1995; Maccoby & Jacklin, 1974; Woolley, 1914).1 Research findings are sometimes misunderstood. Generalizations from those findings are provocative (Ceci & Williams, 2007). Because most effect sizes used to quantify mean sex differences in psychological variables are described as either non-existent or “small,” the Gender Similarities Hypothesis has been promoted to replace a “differences” hypothesis (GSH; Hyde, 2005, Hyde, 2014).2
The GSH applies to intelligence and academic achievement variables, broadly speaking. The sexes are similar in general intelligence (Jensen, 1998); however, consistent differences emerge in some specific abilities (Reynolds, Scheiber, Hajovsky, Schwartz, & Kaufman, 2015; Zell, Krizan, & Teeter, 2015). If there is no sex difference in general intelligence, is it worth studying sex differences in specific abilities? We think the answer is yes (cf. Archer, 2019; Hyde, 2014). Findings may shed light on human cognition and have implications for understanding educational progress and achievements. In this commentary we highlight sex differences in specific abilities, especially from findings related to broad cognitive abilities, discuss important matters in such research, and provide suggestions for future research. We focus on empirical descriptions because it has been a focus of our research. We do not address potential explanations for sex similarities or differences, such as those derived from evolutionary (Archer, 2019; Geary, 2021) or sociocultural (Hyde, 2007, Hyde, 2014) theories, among others (see Eagly & Wood, 2013).
Section snippets
IQs and g
Substantial and reliable mean differences between the sexes have not materialized in either general intelligence (psychometric g)3 or intelligence in general (e.g., IQs). This finding is germane to the study of sex differences in
Broad and narrow/specific cognitive abilities
We reference Cattell-Horn-Carroll (CHC) theory (Carroll, 1993; Horn & Noll, 1997; Schneider & McGrew, 2018) to highlight and describe sex differences in specific abilities. CHC theory is widely used for intelligence research, test development, and assessment (Caemmerer, Keith, & Reynolds, 2020; McGrew, 2009). CHC theory is useful for classifying and organizing cognitive abilities (Reynolds, Keith, Flanagan, & Alfonso, 2013). Likewise, it is useful for organizing research findings. In this
Broad and specific academic achievement abilities
Sex differences in academic achievement scores are often included in descriptions of intelligence differences. The development of these achievement areas relies more on formal academic instruction, however. There are also many more large datasets available for achievement scores (e.g., National Assessment of Educational Progress). Here we discuss sex differences in writing, mathematics, and reading test scores, but do not summarize effect sizes. There are too many studies to summarize,
Important considerations for research in sex differences and specific abilities
Establishing empirical facts is essential to understanding sex differences–easier said than done. Study design and psychometric and participant sampling are critical, as selected measures and samples provide selected results. We address two matters in more detail. We are not the first researchers to address them, but they are worth reiterating and we offer some suggestions for future analyses.
Conclusion
The GSH shifted focus from differences to similarities between sexes. The shift, with the intent to promote more equality among the sexes, is noble. Regrettably, the GSH is at times interpreted to mean that no important sex differences exist in psychological variables. Likewise, similarities in general intelligence may be interpreted incorrectly to mean no important sex differences exist in human cognitive abilities. Here, using CHC theory as a guide to structure findings, we highlighted
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