You're in a new town for the night and looking for a bite to eat. Walking down Main Street, you see a couple possibilities: a crowded diner and a nearly empty hamburger joint. Which do you choose?
Eating preferences aside, chances are you would choose the crowded diner. Psychologists, economists and advertisers have long shown that people make decisions largely based on what others do. But what if the newcomer were a rat, not a person? And the choice in question was between two piles of rotting garbage?
It turns out non-human animals, too, make decisions based on watching each other. Norway rats, for example, smell the scent of foods recently eaten on the whiskers and fur of other rats and base their meal choice on these odors. Birds, meanwhile, such as starlings and red crossbills, watch their neighbors when looking for prey. If others are having success in a particular patch, they'll stick around. If not, they try their luck elsewhere.
Etienne Danchin of the Pierre and Marie Curie University in Paris argues in the current issue of Science that the use of so-called public information is widespread in the animal kingdom and may lead to the development of a kind of culture within animal species that, in turn, affects evolution.
"Social information is a big thing for animals when making decisions," said Thomas Valone, a biologist at St. Louis University and coauthor of the study. "We're saying it's another piece of information that biologists should pay attention to when we try to understand evolution."
Eating isn't the only area where animals appear to take cues from one another. Other research shows social information is also important when animals are choosing where — and who — to mate.
Studies of antelopes, for example, suggest that females base their selection of breeding sites on the smell of other female antelope's urine in the soil.
When scientists transplanted soil from successful mating territories to less successful ones, female antelopes new to the areas always chose the territories with soil scented with successful females — regardless of the location.
"There is apparently something in the urine of successful mating females that others pick up," said Valone.
When it comes to choosing mates, following others' mate choices sometimes takes priority.
Female guppy fish, for example, normally choose the most brightly colored males for mating. Evolution theory explains this preference this way: Brightly colored fish are more vulnerable to predators, so any brightly colored males around must be especially fit and adept at avoiding being eaten and therefore good dad material.
But this rule of thumb changes when female guppies observe other females choosing duller colored males.
In experiments, female guppies were placed in glass tanks where they could see another female guppy in adjacent tanks giving a dull colored male more attention than a brightly colored one (the observer could not realize this was because the brightly colored one was sequestered in a separate tank).
When the female observer was then placed in a tank with both the dull and brightly colored males, the female nearly always chose the dull-colored one — since this was the one she saw cavorting with the other female.
Where does this kind of information-sharing lead a species? Danchin argues it spurs the creation of a culture of sorts, which can influence the turn of evolution. By learning from each other, animals don't have to go through trial and error on their own to find the best strategies. That means the course of evolution gets a boost.
Some so-called cultures stemming from information sharing include local populations of birds that sing in particular dialects. The accents develop as females learn from each other to choose males with the local accent. The same trait has been observed in dialects of songs by South Pacific sperm whales.
But do these kinds of local traditions truly make up a culture? Evolutionary anthropologist Francisco Gil-White of the University of Pennsylvania says not quite. It takes more than one or two locally learned traits to make up a culture, he says. And, when it comes to information sharing and culture, he argues, there's no comparison between humans and other animals.
"More than any other animal, humans are obsessed with copying each other's behavior," he said. "This sets the stage for the creation of politics, science, arts and the human experience."
Gil-White argues that mimicking each other's behavior — especially the behavior of successful people like athletes and celebrities — is so important in human nature that people learn to "kiss up" to these successful models. By "kissing up" to successful people, others hope to learn more from them and imitate their successful traits.
"What evolves is a pattern of kissing up where the people who have less good information are giving favor to those who appear to have more," he said.
It doesn't stop there, he says. Successful models, meanwhile, learn to act modest and gentle in order to reap more favors from admirers and imitators. Traits like taking a bow or self-deprecating behavior, he says, are completely unique to people.
Antelopes, birds and fish may not feign modesty to win favor, but Valone says, the fact that they learn from one another, is important to understanding why they act the way they do.
"Most of the time, we focus on genetic components of animal behavior," he said. "But information sharing may be as important when animals make decisions."