Research Article: The magnitude of sex differences in verbal episodic memory increases with social progress: Data from 54 countries across 40 years

Date Published: April 22, 2019

Publisher: Public Library of Science

Author(s): Martin Asperholm, Sanket Nagar, Serhiy Dekhtyar, Agneta Herlitz, Stephen D. Ginsberg.

http://doi.org/10.1371/journal.pone.0214945

Abstract

Sex differences in episodic memory have been reported. We investigate (1) the existence of sex differences in verbal and other episodic memory tasks in 54 countries, and (2) the association between the time- and country-specific social progress indicators (a) female to male ratio in education and labor force participation, (b) population education and employment, and (c) GDP per capita, and magnitude of sex differences in verbal episodic memory tasks. Data were retrieved from 612 studies, published 1973–2013. Results showed that females outperformed (Cohen’s d > 0) males in verbal (42 out of 45 countries) and other (28 out of 45 countries) episodic memory tasks. Although all three social progress indicators were, separately, positively associated with the female advantage in verbal episodic memory performance, only population education and employment remained significant when considering the social indicators together. Results suggest that women’s verbal episodic memory performance benefits more than men’s from education and employment.

Partial Text

The presence of sex differences in some but not all cognitive functions is well documented [1]. For example, women are often reported to have an advantage in verbal production [2], reading comprehension [3], and episodic memory (recollection of past experiences in terms of their content, location, and temporal occurrence; [4, 5]), while men often perform at a higher level on visuospatial [6, 7] and some numerical tasks [8–10]. These sex differences are typically modest in size and the underlying mechanisms are not yet sufficiently understood. Despite this, they have consistently been reported from early childhood into old age, and in most examined regions of the world, although their magnitude seems to vary across countries [3, 5, 8, 10–14]. Here, factors contributing to the variation in magnitude of sex differences in episodic memory will be examined.

Two separate five-level random effects meta-analyses with country as moderator were computed for both the datasets Verbal (Fig 1A) and Other (Fig 1B) to assess the overall pattern of sex differences and variation in magnitude of sex differences across countries. For Verbal episodic memory tasks, there was an overall female advantage (d = .27; CI = [.24, .30]; p < .001) that was seen in most countries (i.e., Cohen’s d > 0 in 42 out of 45 countries), although the sex difference was not statistically significant in all of them. The moderator analysis showed a statistical significant impact of country (QM (df = 44) = 185; p < .001), justifying subsequent analyses trying to explain this variation. The aims of this study were (1) to determine the existence and magnitude of sex differences in episodic memory tasks across countries, and (2) to investigate if and how societal changes—in terms of time-specific national indicators of gender equality, educational level and labor force participation, and economic development—were associated with the magnitude of sex differences in episodic memory. These questions were addressed in a large dataset, including 612 studies originating from 54 countries, spanning over 40 years. In line with our hypothesis, results showed that there was an overall female advantage for Verbal episodic memory, found in 42 of 45 countries although not reliably so in all. Other episodic memory tasks also yielded an advantage for women, although smaller, found in 28 of 45 countries. Furthermore, results indicated that all three social progress indicators were, independently, positively associated with the female advantage in Verbal episodic memory performance. Population Education and Employment was the most important predictor among the three indicators for Verbal episodic memory, contrary to our hypothesis that gender equality would be the strongest predictor. The results of the current study indicate that the female advantage in episodic memory is present in most countries. The results also suggest that the advantage in verbal episodic memory tasks is further heightened in countries with higher population education and labor force participation, likely serving as proxies for increased education, heightened cognitive stimulation, and a more enriching environment. Although it is still an open question why women seem to be more positively affected by these societal improvements than men, it can be hypothesized that women benefit disproportionately because they may start from a more disadvantaged level. More research into these questions is warranted.   Source: http://doi.org/10.1371/journal.pone.0214945

 

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