Males who frequently engaged in extreme binges had exaggerated deficits on one of the visuospatial tasks, as did their female counterparts on the social-cognitive task, suggesting sex-specific vulnerabilities

Frequency of Recent Binge Drinking Is Associated With Sex-Specific Cognitive Deficits: Evidence for Condition-Dependent Trait Expression in Humans. Liana S. E. Hone et al. Evolutionary Psychology, October-December 2020: 1–13. https://journals.sagepub.com/doi/pdf/10.1177/1474704920954445

Abstract: Evolutionary theory suggests that commonly found sex differences are largest in healthy populations and smaller in populations that have been exposed to stressors. We tested this idea in the context of men’s typical advantage (vs. women) in visuospatial abilities (e.g., mental rotation) and women’s typical advantage (vs. men) in social-cognitive (e.g., facial-expression decoding) abilities, as related to frequent binge drinking. Four hundred nineteen undergraduates classified as frequent or infrequent binge drinkers were assessed in these domains. Trial-level multilevel models were used to test a priori Sex  Group (binge drinking) interactions for visuospatial and social-cognitive tasks. Among infrequent binge drinkers, men’s typical advantage in visuospatial abilities and women’s typical advantage in social-cognitive abilities was confirmed. Among frequent binge drinkers, men’s advantage was reduced for one visuospatial task (delta d = 0.29) and eliminated for another (delta d = 0.75), and women’s advantage on the social-cognitive task was eliminated (delta d = 0.12). Males who frequently engaged in extreme binges had exaggerated deficits on one of the visuospatial tasks, as did their female counterparts on the social-cognitive task. The results suggest sex-specific vulnerabilities associated with recent, frequent binge drinking, and support an evolutionary approach to the study of these vulnerabilities.

Keywords: sex differences, sexual selection, alcohol, binge drinking, cognitive deficits, vulnerabilities

Discussion

There is now consistent evidence that men generally have better developed visuospatial abilities than women (e.g., Hyde, 2005; Jones et al., 2003; Lawton, 2010; MacDonald & Hewlett, 1999), whereas women generally have better developed socialcognitive skills than men (e.g., Hall, 1984; Merten, 2005; Thompson & Voyer, 2014). The magnitude of these sex differences varies across context, and an evolutionary perspective can situate these contextual influences in the framework of sexual selection (Darwin, 1871). Sexual selection in the context of human evolution includes visuospatial (favoring men) and social-cognitive (favoring women) sex differences that confer advantages in competition for mates or other reproductively important resources and discriminative mate choice under favorable conditions (Geary, 2021). Following Zahavi (1975) and research on condition-dependent trait expression in nonhuman species (Cotton et al., 2004; Johnstone, 1995), Geary (2015, 2019) proposed that these sex differences are condition dependent in humans, such that their development and expression is a reliable indicator of exposure to, and resistance to degradation by stressors. The current study is the first to directly test this hypothesis in humans, and to propose that recent, frequent binge drinking acts as a neurotoxic stressor disrupting cognitive abilities in sex-specific ways. The typical advantages of men in visuospatial abilities (Voyer et al., 1995) and of women in social-cognitive abilities (Hall, 1984; Thompson & Voyer, 2014) were replicated among a group of emerging adults who never or rarely engaged in binge drinking in the past month. These sex differences were greatly attenuated or even reversed in a group of emerging adults who at least occasionally engaged in binge drinking in the recent past. Given the prevalence of binge drinking in this population—current estimates place the percentage of college student binge drinkers at 40%–50% (Croteau & Morrell, 2019; Krieger et al., 2018)—these findings suggest that sex-specific deficits among college students might be widespread. Recent data also indicate that although the prevalence of binge drinking among adolescents has declined in recent years (Chung et al., 2018), emerging and young adults are engaging in more binge drinking than in the past, reflecting a secular shift in the age of peak binge drinking (Patrick et al., 2019). These high prevalence rates and increasing age of peak heavy episodic drinking are especially concerning in light of the current findings, given that mate competition and choice are most intense during this developmental period. During the years that coincide with elevated binge drinking rates, competition for mating-relevant resources peaks and creates a period of high risk and high reward with regard to engaging in mating effort (Hill & Chow, 2002). Indeed, binge drinking may be an attractive risk-taking behavior to emerging adults in part because it serves as a costly social signal with the potential to yield high gain in a competitive mating market (Aung et al., 2019). As would be expected of sexually selected costly signals (Zahavi, 1975), our findings highlight that binge drinking does indeed come with costs. Under natural conditions, condition-dependent traits are vulnerable to chronic malnutrition, disease, or social conflict and appear to be more sensitive to man-made toxins than other traits (see Geary, 2015, 2019). Although heavy episodic exposure to ethyl alcohol might not be as detrimental as chronic exposure to natural stressors or many other toxins, chronic, heavy exposure to alcohol can result in short-term and sometimes longer-term but subtle deficits in memory and cognition (e.g., Goudriaan et al., 2007). Binge drinking might then reveal sex-specific vulnerabilities in visuospatial and social-cognitive abilities. Some previous studies of alcohol use have assessed similar abilities but sex differences are not always reported (Folgueira-Ares et al., 2017). When they are reported, the pattern of sex-specific deficits is mixed (Haut et al., 1989; Weissenborn & Duka, 2003). These prior studies often have been based on relatively small samples and have used standard neuropsychological measures that typically are not optimal for assessing sex-specific deficits. For instance, there are often small sex differences in spatial working memory and pattern recognition (tasks found in the Cambridge Neuropsychological Test Automated Battery; CANTAB), but sex differences on these tasks are smaller than those found for tasks used in the current study. The difference is important because from an evolutionary perspective, sex-specific vulnerabilities generally will be more evident for traits with larger sex differences (Geary, 2017). Our results provide preliminary evidence in support of this hypothesis. Men’s advantage on both visuospatial tasks was smaller among frequent binge drinkers than among infrequent binge drinkers and non-drinkers. Moreover, there was evidence for a dose-response effect for mental rotation, whereby very high and frequent exposures to ethyl alcohol (extreme binges) were related to worse performance, but only among men. At the same time, these same men did not show exaggerated deficits in the speed of identifying emotions displayed in facial Hone et al. 9 expressions. In judging line angles and position, binge drinking women were more accurate than were binge drinking men, a reversal of the standard sex difference in visuospatial abilities and of our findings for infrequent binge drinkers. We did not, however, find evidence for a dose-response effect for this measure. It is possible that men’s performance on this spatial measure is disrupted by more moderate levels of alcohol exposure with no further deficits emerging with added exposures, but this remains to be determined. In contrast, women who recently engaged in frequent binge drinking did not show visuospatial deficits relative to women who had not engaged in binge drinking, but they were slower at identifying emotions displayed in facial expressions, especially the expressions of other women. Men often display an advantage, relative to women, in judging anger on the faces of other men (see Geary, 2015). Here, this effect did not emerge for facial-expression decoding accuracy, or for reaction time. It is possible that the task used here did not include a sufficient number of angry male faces to provide a powerful test of this effect (which was not a primary focus of this study). There also was evidence of a dose-response effect in this measure, restricted to women. That is, women who frequently engaged in extreme binges were slower at emotion detection than were other women, but these same extreme binge drinking women did not show exaggerated deficits for mental rotation. This pattern is essentially a mirror image of that observed among men who frequently engaged in extreme binges. Nevertheless, follow-up studies with larger sample sizes of binge drinkers are need to determine if there are indeed sex-specific doseresponse effects for visuospatial and social-cognitive abilities. The overall pattern of sex-specific deficits found here is consistent with the expression of condition-dependent traits in other species (Cotton et al., 2004; Johnstone, 1995), and supports the more general hypothesis that the sex differences in visuospatial and social-cognitive abilities stem from different patterns of intrasexual competition among our male and female ancestors, respectively (Geary, 2015; Geary et al., 2014). Although this study was designed based on established predictions (Geary, 2015, 2019) that provided for a priori hypothesis testing based on well-established patterns in nonhuman species, the study provides only a quasi-experimental test of those predictions. It is possible that the differences we observed across frequent and infrequent binge drinkers preceded recent drinking episodes, as suggested by modestly lower vocabulary scores among the binge drinkers. If there were broader cognitive differences across the drinking groups, however, then the frequent binge drinkers should have performed more poorly than infrequent binge drinkers on all cognitive tasks, independent of sex and not in a sex-specific manner. Moreover, because vocabulary is a good indicator of general intelligence, any binge drinking group differences on the visuospatial and social-cognitive tasks should have disappeared with statistical control of vocabulary scores, but they did not. Different psychopathologies can also affect cognitive performance, for instance psychomotor slowing of responding in subjects with depression and anxiety (Bennabi et al., 2013; Gualtieri & Morgan, 2008). While we did not measure this in our study, and therefore could not fully control for this potential third variable, it is an interesting hypothesis to pursue in future studies. Concomitant drug use was also not measured, but can still influence cognitive performance (Davis et al., 2002; Quednow, 2017). It is currently unknown if drug use mitigates the interactive effects found here, or has an additive effect along with binge drinking frequency. Additionally, and as always, readers should interpret the results presented here with care in terms of multiple comparisons and post-hoc contrasts. Future research would benefit from the use of a longitudinal design that would permit assessment of changes in performance on measures of purported sexually selected traits over time, as a function of changes in binge drinking frequency. Although also not an experimental design, this kind of approach would permit stronger inferences regarding the role of recent binge drinking frequency by accounting for any preexisting differences across participants in their baseline levels of performance. Findings from such a study would further advance understanding of the extent to which exposure to this very common neurocognitive stressor specifically impairs abilities that evolutionary theory posits to be critical for sexual selection success. Despite these caveats, our results are unique and speak to the utility of using sexual selection as a means to identify and study sex-specific vulnerabilities, not just those associated with binge drinking but with exposure to myriad other potential stressors and toxins.