Men’s and women’s faces tend to differ, on average, in several ways. For instance, men’s faces tend to have longer and broader chins, more prominent cheekbones, smaller lips, and more pronounced brow ridges (making men’s eyes appear smaller and narrower relative to women; see Gangestad & Scheyd, 2005). Of course, not all men have large chins and cheekbones.

Those men who do, those who possess more “masculine” faces, tend to be rated as more attractive by some women, but not all women (Little et al., 2001; Quist et al., 2012; Penton-Voak et al., 2003; Perret et al., 1998). Researchers working from an evolutionary perspective have suggested women may express greater preferences for masculine faces when they reside in environments with higher pathogens because facial masculinity is an important clue to a man’s health, genetic quality, and immunocompetence, all of which may be more imperative when making a mate choice in a high pathogen context (Cantú, 2013; DeBruine et al., 2010; Gangestad & Eaton, 2012; Gangestad et al., 2006).

A new study by Isabel M. Scott and her colleagues (2014) looked at women’s (and men’s) face preferences across a dozen cultures and their findings have been promoted in several media outlets (http://www.sciencedaily.com/releases/2014/09/140923142733.htm; http://www.brunel.ac.uk/chls/life-sciences/news-and-events/ne_385097; http://phys.org/news/2014-09-manly-men-feminine-women-linked.htmlhttp://www.detroitnews.com/story/news/nation/2014/09/27/evolution-face-science/16331599/; http://www.designntrend.com/articles/20185/20140926/facial-features-mate...), with some claiming their new findings seriously challenge evolutionary explanations of women’s sexual desires. In particular, the new findings have been portrayed as refuting the idea that women within high pathogen cultures report more desire for masculine faces. This is a fascinating study. I have great respect for these researchers and their ability to collaborate on such an interesting topic with such a diverse array of samples. Major kudos.

I also agree with their general conclusions that market forces and factors beyond pathogens are needed to fully explain women’s (and men’s) varying sexual desires across cultures, including the speculation that because more urban individuals are exposed to more diverse faces they may develop more nuanced face preferences. All of that is great science in my view, even if speculative. However, regarding the more sensationalist media reports (with major aspects of evolutionary psychology described as “crumbling” in response to the new findings), several caveats should be noted about the broader picture of what these researchers actually found and what their findings actually mean for sexual science. 

That’s a Lot of Cells

Scott et al. (2014) examined expressed mate preferences across a very diverse set of cultures—ranging from modern market economies to pastoral, horticultural, and even foraging cultures. This is an impressive feat. These researchers looked at much more than just cultural factors. Mate preferences were contrasted across men versus women evaluators, long-term versus short-term temporal contexts, and 3 different types of face stimuli were used (masculine, neutral, and feminine faces). They examined all of these variables in combination across 12 populations. That’s a complex experimental design. Actually, it was even more complex than that (they looked at perceived aggression, too), but to simplify, we have here a 2x2x12 mixed experimental design with 3 choices as the dependent variable. Statistically-speaking, that’s a lot of cells to possibly compare, with many questions that could be asked and answered in slightly different ways. Two questions were most central to the study’s authors and its subsequent media exposure.

As Scott et al. (2014) noted…past research (much of it done by these same authors, by the way) has shown “preferences for masculinity are stronger in circumstances where indirect benefits (heritable quality) can be realized without accompanying direct costs (aggression and low paternal investment). Such circumstances include judging attractiveness in the context of a short-term (vs. a long-term) relationship.”

In other words, women may prefer masculine men generally, but in the long-term men’s extreme masculinity poses problems for women (e.g., a highly masculine man might be more aggressive and more likely to cheat as he is highly desirable to women). When evaluating short-term mates, women care less if he cheats, and so a key prediction is:  Women should prefer masculinity in men more in short-term mates than in long-term mates.

Scott et al. (2014) also noted “Masculinity is also reported to be more strongly preferred in environments with relatively high pathogen burdens.” So a second prediction is that women should prefer more masculine faces in high pathogen cultures than in low pathogen cultures. Previous studies have found support for this prediction, again explaining that facial masculinity may be a clue to a man’s health, genetic quality, and immunocompetence, all of which may be more important in high pathogen cultures. Previous studies focused mostly on women’s long-term or general preferences; I’m unaware of previous work on women’s short-term preferences for masculinity shifting across cultures (other than in this cool new study!).

Testing the Predictions

The media has paid more attention to findings concerning the latter of these two predictions. Masculine male faces were not more intensely preferred by women within high pathogen (or low development) cultures. This is a correct interpretation of their findings (overall, the opposite was found for women’s long-term mate preferences, no significant associations with development were found for women’s short-term preferences). As reported by Scott et al. (2014) “contrary to our predictions, the HDI [a measure of high development, which is normally associated with lower pathogens] was positively associated with preferences for masculinity in the long-term relationship context (z = 2.08, P = 0.038). There was much higher variability, and no significant relationship, in the short-term context.”

This finding regarding long-term mate preferences is at odds with previous theory and research (both correlational and experimental) using samples from more modern nations that has examined women’s general or long-term mate preferences (DeBruine et al., 2010; Gangestad et al., 2006; Jones et al., 2013; Little et al., 2011; Little et al., 2007; Moore et al., 2013; Penton-Voak et al., 2003). For instance, DeBruine et al. (2010) reported average masculinity preferences were negatively correlated with national health indexes, “demonstrating that average masculinity preference increased as national health decreased.” Gangestad and Buss (1993) and Gangestad et al. (2006) found both men and women particularly prefer “physically attractive” mates as parasite prevalence increases across cultures, though the precise attributes that are preferred [masculine or feminine] remain unspecified within these studies.

Overall, these newly conflicting findings make for an exciting advance in evolutionary science. I think future research efforts should flood into this area to figure out what is going on (see Gangestad & Eaton, 2012 for a nuanced interpretation of these issues). However, before we stick a fork in the whole of evolutionary psychology (as some media outlets would claim it is “crumbling”), it may be worth reflecting on some methodological limitations and more nuanced conclusions that might be taken from this study.

We’re Gonna Need a Bigger Sample Size

The breadth of the samples in Scott et al. (2014) study is remarkable. However, the size of most samples was extremely small (understandably so, given the difficulty in securing access to these remote populations), with women’s effective sample sizes including 5 Fijian women, 11 Aka women, and 13 Cree women, for instance. For many of their samples, such samples sizes are probably too small (lack enough statistical power) to reveal true empirical associations, if any exist, across sex, temporal context, facial dimorphism, and culture.

For instance, Roney et al. (2006) found an effect size of approximately d = .22 for the link between male facial masculinity and women’s ratings of men’s short-term attractiveness, a link of that magnitude would require sample sizes of at least 200 women (with 80% power and alpha at .05) for researchers to be reasonably confident they would observe a link between male facial masculinity and female short-term mating desires if the link really existed. A total of 5 Fijian women is simply not enough to be confident in evaluating whether true links exist between male facial masculinity and women’s short-term mate preferences. This sample size problem is further exacerbated by the three-face choice methodology, which leads to even greater power concerns.

Why Include Neutral Faces?

Recall that Scott et al. (2014) presented participants with 3 facial stimuli to choose as attractive—masculine, neutral, and feminine faces (an ordinal variable). The decision to include a “neutral” face likely reduced the likelihood of finding statistically significant differences across masculine and feminine faces (for both men and women, across both short-term and long-term contexts). Indeed, the inclusion of a neutral face condition (which in many samples was chosen about 33% of the time, generating the appearance of mate choice randomness) seriously clouds the interpretation of these findings. One cannot know whether the neutral choice was for some participants a close choice between masculine and neutral, but for other participants a close choice between feminine and neutral.

Given the key hypotheses in this area were specifically about masculine versus feminine face preferences (with no explicitly stated hypothesis about neutral face preferences versus others), the decision to employ this three-face methodology was unfortunate (particularly given the low sample sizes). Had the sample sizes been considerably larger, the noise generated by neutral face would be less troublesome, perhaps even revealing. For example, one could evaluate whether women’s short-term desires are driven more by attraction to masculinity or repulsion from femininity (relative to the neutral condition; see Rennels et al., 2008). Still, if you are principally interested in whether people like Coke versus Pepsi, there’s no real need to give them a third choice of a Coke-Pepsi mixture. Participants who choose the mixture are not providing a lot of details about their Coke versus Pepsi preferences. For the hypotheses of this study (and given the small sample size), the neutral face probably reduced power more than it helped inform theory.

Additional Findings of Note

Regardless, this is an amazing group of samples and the reported empirical findings—limited by sample size and hindered by methodology—are still quite interesting. Here are 3 findings that have not received as much media attention as the presumably anti-evolutionary psychology findings:

1) Results from the only exclusively foraging culture in the study (the Aka, as described by Scott et al., 2014), demonstrated that among the foraging Aka, women preferred more masculine male faces for short-term mating, and preferred more feminine male faces for long-term mating, as did the Tuvans; “Aka and Tuvans showed a preference for masculinized faces in short-term relationships (P = 0.005 and P < 0.00001, respectively) and for feminized faces in long-term relationships (P = 0.017 and P = 0.0003, respectively).” This is precisely what would be expected from several evolutionary perspectives.

Given humans evolved for most of our history as a species as foragers, this finding could be reasonably interpreted as especially strong support for evolutionary psychology predictions that women possess dualistic mating strategies, such that women prefer more masculine men as short-term mates and less masculine (more paternally reliable) men as long-term mates (see Thornhill & Gangestad, 2008, The evolutionary biology of human female sexuality).

It should be noted that sometimes women do express preferences for masculine men as long-term mates, particularly when women are shown images of men engaged in direct physical competition, images of weapons, or images depicting items of high monetary value (Little et al., 2013), when women are already mated (Little et al., 2002), when women have reason to believe a highly masculine man will be sexually faithful (Quist et al., 2012), and when women are of high mate value, themselves (perhaps because they can “afford” a highly masculine man as a long-term mate, as they consider themselves valuable enough for him not to consider cheating; see Little et al., 2001; Penton-Voak et al., 2003). Women with higher mate value do not increase their desires for male masculinity in potential short-term mates, however (Little et al., 2001; Penton-Voak et al., 2003). Ideally, these and other potentially moderating variables should be addressed in future cross-cultural work in this area.

2) Scott et al. (2014) found UK, Kadazan, and Canadian women also expressed more intense preferences for masculine faces when evaluating men as short-term mates, as predicted from dualistic mating strategy perspectives. Hangzhou women preferred masculine faces across both short-term and long-term contexts, whereas women in 4 samples generally preferred the neutral male face, and in 2 samples women generally preferred the feminine male face overall.

3) Scott et al. (2014) found men generally preferred more feminine faces in “Canadian, Fijian, Hangzhouvian, Kadazan, Shanghainese, Cree, and UK populations.” The Miskitu and Tuvans males also preferred feminine faces for long-term (but not short-term) faces. Men’s preferences for more feminine faces have been found in previous studies (see Gangestad & Scheyd, 2005), though I’m unaware of studies showing differences between long-term and short-term mating contexts for men’s feminine facial preferences.

Men especially preferred more feminine faces in higher development (or lower pathogen) nations. Of course, finding these preferences were more intense in higher development (or lower pathogen) nations does not negate the prevalence of the preferences across most (but not all) nations. Overall, the male findings generally supported evolutionary psychology predictions concerning femininity-related facial mate preferences of men.

Conclusions

Extremely small sample sizes and the inclusion of a neutral face condition render many of these findings as rather limited in scope and consequence. Even so, among several nations (including the foraging Aka) women preferred more masculine men for short-term mates and less masculine men for long-term mates, whereas men tended to prefer more feminine faces across most samples.

As with most studies, more research is needed, bigger sample sizes, cleaner designs, and so forth. Science marches on. Hopefully, future sexual science on human mating will include more studies like this one utilizing samples that are non-WEIRD (non-Western, Educated, Industrialized, Rich, and Democratic; Henrich et al., 2010). By the way, for critics of evolutionary psychology, it may be worth noting that studies of non-WEIRD samples are much more typical among evolutionary psychologists than other types of psychologists (see http://www.epjournal.net/blog/2013/09/is-evolutionary-psychology-weird-or-normal/). Just saying.

References                                                                                      

Cantú, S.M. (2013). When are women especially attracted to attractive men? Human mate preferences in a pathogen prevalent ecology (Doctoral dissertation, UNIVERSITY OF MINNESOTA).

DeBruine, L.M., Jones, B.C., Crawford, J.R., Welling, L.L., & Little, A.C. (2010). The health of a nation predicts their mate preferences: Cross-cultural variation in women's preferences for masculinized male faces. Proceedings of the Royal Society B: Biological Sciences, rspb20092184.

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