“Why are you putting on your shoes? They won’t help you outrun the bear!” To which the second man calmly responds: “I don’t need to outrun the bear; I just need to outrun you.”
It is this same reasoning that drives ever-larger numbers of people to have plastic surgery and with greater frequency. Liposuction might yield a physical advantage for early adopters, but when everybody gets it done, the advantage goes away. As a result, people then demand other kinds of plastic surgery in a kind of silicone arms race. The breadth of services demanded explodes to parallel the spread of services through the network.
Competition for mates can actually be quite stressful. One investigation we conducted suggests that the higher the male-to-female ratio at a time when a man reaches his early twenties, the shorter his life. A man who is surrounded by other men has to work harder to find a partner, and this environment of elevated competition has long-term consequences for his health. In this regard, we are no different from a number of animal species. In one analysis, we examined the effect of the gender ratio in a sample of high-school seniors in Wisconsin in 1957—a total of 4,183 young men and 5,063 young women in 411 high schools. We found that men in high-school graduating classes with lopsided gender ratios (of more men) wound up with shorter life spans fifty years later. In another analysis of more than 7.6 million men from throughout the United States, we found that the availability of marriageable women again had a durable impact on men’s health, affecting their survival well into their later years.14
These results suggest that the people who surround us are not only a source of partners or of information about partners; they also are our chief competitors. As a result, the social network in which we find ourselves defines our prospects. It does so by defining whom we meet, by influencing our taste in what is deemed desirable in a partner, and, finally, by specifying how we are perceived by others and what competitive advantages and disadvantages we have. You don’t need to be the most beautiful or most wealthy person to get the most desirable partner; you just need to be more attractive than all the other women or men in your network. In short, the networks in which we are embedded function as reference groups, which is a social scientist’s way of saying “pond.”
In the 1950s, Robert K. Merton, a very influential social scientist, codified the basic ways that reference groups affect us: they can have comparative effects (how we or others evaluate ourselves), influence effects (the way others dictate our behaviors and attitudes), or both.15 Having unattractive social contacts may make us feel superior (comparison) but may also make us take worse care of ourselves (influence). These two effects may work at cross-purposes in our quest to find a partner.
For decades, reference groups have been seen as abstract categories: people often compare themselves to other “middle-class Americans” or other “members of their grade at school” or other “amateur soccer players.” But exciting advances in network science are now enabling us to map out exactly who these references group are for each person. Many people may be more attractive than we are, but our only real competitors are the people in our intended’s social network.
Everyone Else Is Doing It
People we know influence how we think and act when it comes to sex. To begin with, both friends and strangers affect our perceptions of a prospective partner’s attractiveness, consciously and unconsciously. These effects go beyond basic tendencies that men and women have to make judgments about appearance; for example, it has repeatedly been shown that men find women with low waist-to-hip ratios more attractive, and women value certain facial features in men. Until recently, most research on partner choice and assessments of attractiveness has focused on an individual’s independent preferences. Yet there are good biological and social reasons to suppose that perceptions of attractiveness can spread from person to person.
An experiment suggests how. First, investigators took pictures of men who were rated equally attractive by a group of women.16 Then, they presented pairs of pictures of two equally attractive men to another group of women, but between each pair of pictures, they inserted a picture of a woman who was “looking” at one of the men. This woman was smiling or had a neutral facial expression. The female subjects were much more likely to judge a man to be more attractive than his competitor if the woman interposed between the photos was smiling at him than if she was not.
In another study, a group of women again rated photographs of men for attractiveness. The photos were accompanied by short descriptions, and when the men were described as “married,” women’s ratings of them went up.17 In still another study, men in photographs with attractive female “girlfriends” were judged to be more attractive when the “girlfriend” was in the photo than when she was not. Having a plain “girlfriend,” however, did not enhance a man’s appeal as much.18 And, astoundingly, women’s preferences for men who are already attached may vary according to where the women are in their menstrual cycles. When they are in the fertile phase of the cycle, they have a relative preference for men who are already attached to other women.19
There is thus a kind of unconscious social contagion in perceptions of attractiveness from one woman to another. This makes perfect sense from an evolutionary perspective. Copying the preferences of other women may be an efficient strategy for deciding who is a desirable man when there is a cost (in terms of time or energy) in making this assessment or when it is otherwise hard to decide. While a woman can, with a glance, assess for herself various attributes of a man that might be associated with his genetic fitness (his appearance, his height, his dancing ability), other traits related to his suitability as a reproductive partner (his parenting ability, his likelihood of being sweet to his kids) can require more time and effort to evaluate. In those cases, the assessment of another woman can be very helpful. In fact, psychologist Daniel Gilbert has shown that a woman can do a better job of predicting how much she will enjoy a date with a man by asking the previous woman who dated him what he is like than by knowing all about the man.20 This fact has been exploited for commercial purposes: there is a matchmaking website that only allows men to post if they are “recommended” by a former girlfriend.
In direct mate choice, you choose who you like, but in indirect mate choice of the sort we have been considering, you choose who others like. Indirect mate choice can even lead people to choose mates with characteristics that they did not previously care about. A slight preference by some women for men with tattoos, for example, can lead hordes of men to get tattoos and inspire other women to want men who have them.
Perhaps not surprisingly, men react differently to social information. While they clearly have shared norms about what is attractive in a woman, contextual cues in men can actually operate in the opposite way.21 College-age women were more likely to rate a man as attractive if shown a photograph of him surrounded by four women than if shown a photograph of him alone. But college-age men were less likely to rate a woman as attractive if she was shown surrounded by four men than if she was shown alone. This makes evolutionary sense: when selecting mates, males tend to be less choosy than females and so are less concerned with the opinions of anyone else to begin with. But the presence of other men conveys information of a different sort, namely, that there might be time-consuming (and stressful) competition to secure the woman’s interest.
Hence, social networks affect our relationships in two important ways. First, structural features of our position in the social network can affect whether people think we are attractive. Do we have a partner already? How connected are we? Do we have many or few partners and friends?
