The copycat mating game

December 06, 2000

When you're single no one wants to know. Yet the minute you get a partner, the others come running. Ever wondered why, asks Jonathan Knight

BEFORE I got married a few weeks ago, friends told me that flashing a wedding ring was a sure way to attract female attention. Some said it was because women consider married men to be safe. Others said a wedding band is a quick way for women to identify a quality mate, one that's been pre-filtered by someone else.

So in the interests of science, I have been spending more time in bars lately. As I sip my pint of California microbrew, I keep my left hand clearly visible and wait. And wait. So far, I would call the results inconclusive.

It's really not all that far-fetched an idea, though. Females of other species copy the preferences of their peers all the time. Female quail, for example, prefer a male they have just seen copulating. And female guppies go for the more popular male, even if he is a bit of a wimp. Now researchers at the University of Louisville, Kentucky, have compelling evidence that people-particularly women-engage in mate copying too. Just hearing that other women want to date a man piques their interest.

The effects of peer attention could factor into a variety of social phenomena: why a bushy beard and tangled locks were sexy in the seventies but today's hair can't be short enough, or why teens pierce parts of their bodies adults rarely even think about. They could help explain the unexpected sex appeal of Mick Jagger or Jack Nicholson, and may be at work in celebrity of all kinds. Everyone wants to be unique, but when it comes to mating, imitation appears to have some powerful evolutionary advantages.

Until recently, all the evidence of mate copying has come from fish and birds. That's partly because it's easier to spot in these animals than in humans. Male grouse, for example, gather at special sites called leks where all the action takes place. Leks are the grouse equivalent of a singles bar. Here they strut around displaying their feathers in the hope of pulling a bird. Females wander through the lek, choose a male, mate on the spot-here the singles bar analogy breaks down a bit-and then head off into the undergrowth to nest. Some males on the lek have all the luck. The most successful may win up to 80 per cent of the passing females. So what do the females see in these Casanovas? Some researchers suspected that mate copying was initiating a snowball effect: once a few females chose the same guy, the rest would come running. In 1994, behavioural biologists tested this idea by placing several stuffed female dummies on a black grouse lek near randomly chosen males. The eager cocks courted and mounted the dummies, sometimes for up to half an hour, which gave passing females lots of time to notice. Sure enough, the lucky males ended up mating with more real females on that day than either the day before or the day after.

Other experiments in the lab showed a similar effect in fish known as river bullheads. Unlike male grouse, who play no part in raising their offspring, bullhead males are attentive fathers. They guard the eggs and stay with hatchlings until they are old enough to survive on their own. And female bullheads will always try to spawn with males that already have nests containing eggs. It looked as though both grouse and fish females were copying others as a shortcut to finding a good mate.

True, there are other explanations for these behaviours. In the case of the grouse, the females might simply have been stimulated by the sight of the males' prolonged encounters with the dummies-normal grouse copulations are almost instantaneous. Similarly, bullhead females might have other reasons for their preference. For example, by laying their eggs in nests that are already occupied, they decrease the chances of them being eaten by predators. But such objections to mate copying have been sidelined in recent years, in part because of the work at Louisville by biologist Lee Dugatkin. In 1996, Dugatkin got female guppies to change their mind about which male they liked best solely on account of the preferences of other females. Normally, female guppies like orange. Given a choice, a female will go with the brightest orange male she can find. This may be because the most vividly coloured males tend to be the boldest, and will confront approaching predators. (The researchers added weight to this idea with an experiment in which they trapped a drab male in a glass cylinder and held him right up close to a large fish. Females that saw this happening subsequently preferred this drab male to a more orange one held further away.)

Dugatkin and his colleagues wanted to see if they could override the fish's genetically based preference for orange. They built a fish tank with two smaller tanks attached, one containing an orange male and the other holding a drab one. A female plopped in the middle tank would court the orange male through the glass. The same female was liable to change her mind, however, if she was first held in the middle by a clear cylinder while a second female was trapped by a Plexiglas divider so that she could only swim close to the drab male. For want of anything better, she courted the drab male. When she was removed, along with the dividers, the original female would start courting the drab male rather than the orange one.

Several other cases of mate copying have been reported since then. Last year David White and Bennett Galef of McMaster University in Ontario reported findings from a similar experiment with Japanese quail using cages instead of tanks. In this case, the males were equally "attractive" but one was allowed to mate with a female for ten minutes, while the other was by himself. When the cages were lifted, the female most often courted the male that had just mated. Similar studies have also turned up mate copying in Japanese madaka fish, sailfin mollies and swordtails.

The prevalence of copying suggests it must give the copier some edge in evolution, though exactly what this is remains unclear. One good reason for copying might be that it saves time choosing a mate-time that could be spent doing other things, such as eating or looking out for predators. Or it may be simply that choosing a quality mate is tricky, and by watching what others do, you get more information on which to base this tough choice. This strategy fails, of course, if the individual you copy knows less than you do. But the fact that young guppies tend to copy old ones rather than the other way around suggests that here, at least, copying may be a way of passing down accumulated wisdom.

Birds and fish aren't renowned for their intelligence, though. So perhaps they rely on imitation because they tend not to do much thinking on their own. They follow the flock. They go with the flow. Would independent-minded human beings, with the power of reason and free choice, care about the choices other people make?

To find out, Dugatkin teamed up with psychologist Michael Cunningham, also at Louisville. They presented 166 female undergraduates with a report ostensibly written by five of their peers after a 20-minute interview with a man named Chris. In fact, the five women and Chris were all fictitious. The reports ranked Chris's physical attractiveness on a scale of 1 to 10, and indicated how many of the women were interested in dating him.

The reports rated Chris as either a 3 or a 10 in attractiveness. In addition, four, one or none of the women said she was interested in dating him. Once they had read the reports, the women undergraduates were asked how interested they might be, on a scale of 0 to 6, in dating Chris. A high attractiveness rating raised the women's interest by just over a point on average compared with a low rating. But peer attention had a stronger effect, raising the average dating interest by one-and-a-half points. "The underlying assumption is that he must have something going for him," says Cunningham. "If other people are attracted to him, he must have something they want."

Men are influenced by their peers too, but not nearly as much as women. Running the same experiment on a similar number of men with all the sexes reversed-but keeping the androgynous name, Chris-Dugatkin and Cunningham found that while men responded similarly to the attractiveness ratings, they relied less on other men to decide whether they were interested in Chris. High peer attention boosted their mean interest by less than a point in most of the experiments.

The difference between men and women was even more pronounced when they were asked to rank their interest in marrying Chris. In this case, high peer attention raised the rating given by the men by barely half a point on average, whereas the women's interest jumped by two to three times as much.

This is exactly what evolutionary theory might predict about mate copying. In most species females tend to be more picky than males. That's because they usually invest much more time and energy than males in raising their offspring, so choosing the best mate pays big dividends. Males, on the other hand, can afford to be a bit more cavalier. "So males tend to use a smaller subset of information to determine what they are interested in," says Dugatkin.

What exactly are women looking for in a mate? Dugatkin and Cunningham found that women (and men) were strongly influenced by the peer attention rating when forming opinions about Chris's various attributes. Regardless of the beauty rating, if four peers were attracted they said Chris must have a good sense of humour and good social skills, and, they said, Chris must be wealthy. These qualities are attractive because they suggest that Chris will be a good parent and provider.

Studies suggest that wealth may be particularly important to women. Over a decade ago, David Buss, an evolutionary psychologist from the University of Texas at Austin, surveyed the mate preferences of some 10,000 people across 37 cultures. He found that women universally placed greater importance than men on good financial prospects as well as related factors such as status and ambition. More recent studies show that these factors weigh much less heavily with women in highly paid, high-status jobs, suggesting that the importance women place on wealth is linked to their own socioeconomic status.

To see just how powerful an influence wealth could have on Chris's attractiveness, Cunningham and Dugatkin did another experiment in which they added a description of Chris as a humanities major with the potential to earn only about $20,000 a year. For half of the subjects, they added that Chris's parents had won $10 million in a sweepstake and set up a trust fund for Chris that would pay him $500,000 a year.

Personal wealth

When all other variables were the same, wealthy Chris sparked slightly more interest among both females and males than poor academic Chris. But the impact was much smaller than Dugatkin had expected, possibly because the money said nothing about Chris's abilities. "One reason people would care about wealth is as an indicator of ambitiousness and personality overall," says Dugatkin.

In some sense, then, being a rich person might be like being an orange guppy. Peer attention overrides orange colour in guppies, unless, Dugatkin has found, the guppy is very orange indeed. Then peer attention no longer gets the female to switch. In humans, what counts may be the ability to generate money rather than simply having lots of it. So the question is, if Chris had an earning potential of $500,000 a year, would that override the peer attention effect? It's certainly possible, Dugatkin says, but the experiment has still to be done. What does any of this have to do with everyday life? "The phenomenon of groupies is relevant," says Buss. "You get fairly geeky-looking guys generating a sort of mass hysteria which might be a mate copying phenomenon." Chances are that few teenage girls swooned over John Lennon before the Beatles were famous.

That sort of celebrity then leads directly to another kind of imitation. By the mid-1960s most young men were trying to look like the Beatles, then later Led Zeppelin and Depeche Mode. Today it's Eminem or David Beckham. "Mate copying does help us explain why there is a great deal of variation across societies and across time in what we find attractive about the opposite sex," says Dugatkin. Trends in clothing, hairstyle, even body piercing, are so volatile because of peer attention's snowball effect.

As for the wedding ring effect, the hunt goes on. A few years ago, Cunningham and his colleagues tried an experiment in which women sat alone at a bar with a wedding ring clearly visible. But the results were inconclusive. "Choosing females may have been a tactical error," Cunningham says. "If she is an attractive enough female, whether she has a wedding ring or not, there is a high base rate of being approached."

He has not yet tried the reverse experiment, with men waiting at the bar, in part because the base rate of women approaching men is quite low. Many more hours of observation would be required to detect an effect-as I can personally attest. "The way the ballet usually works is that the female makes eye contact and smiles," says Cunningham. "But it's still the guy who has to get up off his stool and move."

So I'm getting off the stool and heading home. I am, after all, happily married.
This Feature appears in New Scientist issue: 9th December 2000
Jonathan Knight is based in New Scientist's San Francisco office

The Imitation Factor by Lee Alan Dugatkin is published in January 2001 by The Free Press


New Scientist

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