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.
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