For nearly 1,000 years, people used pigeons to ferry messages across vast distances, yet even today, scientists know little about how pigeons and other animals find their way. A new study in the July Journal of Experimental Psychology: Animal Behavior Processes (Vol. 33, No. 3) sheds some light on pigeon's navigation skills and suggests they might do a little preplanning.
University of New Hampshire psychologist Brett Gibson, PhD, looked at how pigeons performed on a standard route-picking puzzle known as the "traveling salesperson" problem. It goes like this: A salesperson must stop at a number of locations, so what's the most efficient route? With only a few locations, humans often find the most efficient possible route, but when there are many stops, they tend to rely on a system known as the nearest neighbor model. Essentially, they repeatedly select the next closest location. While this isn't usually the most efficient route possible, it's often pretty good.
To test the traveling salesperson task with pigeons, Gibson designed a box a foot-and-a-half wide by a foot-and-a-half tall and equipped it with a touch-screen monitor. Pigeons sat in the box and watched dots appear on the screen. Gibson and his team trained them to peck at each dot once. After all dots were pecked, the birds earned a tasty reward. During testing, researchers recorded the path the pigeons took between dots. They found that the pigeons reliably picked a shorter overall path than chance would suggest — they weren't just pecking at random.
But the pigeons were less efficient than humans and they didn't appear to use the nearest neighbor model frequently. Instead, they looked to clusters of dots for their next pecks. So Gibson ran the test again, this time setting criteria — a common trick in animal learning studies. In separate trials, the birds had to pick a route within the top 42, 50 or 66 percent of all possible routes, or else Gibson shut off the lights and made them start over. The stepped percentages let researchers measure the shifts in behavior. Sure enough, the tough-love approach made the pigeons more efficient. What's more, their choices looked more and more like the nearest neighbor model. "When we forced them to be more efficient, they were," Gibson says.
Even though people outperformed pigeons in this task, Gibson says the tables might turn in a natural environment where flying to different locations is required. Pigeons certainly have the edge when it comes to greater distances, as the history of messenger pigeons demonstrates. But all animals face the common problem of efficient travel, Gibson says, and it's not unreasonable to suggest a common cognitive basis for solving that problem.
"We can tap into the cognitive mechanisms animals use in their natural environment," Gibson says. "And they appear to be using the same cognitive structures."