In a world of birds that includes the flamingo, the toucan and the bald eagle, it can't be much fun to be a pigeon. Your plumage options are mostly limited to gray and black, plus an iridescent neck band faintly resembling spoiled luncheon meat. Your song to the extent it exists at all is a tedious cooing, a little like playing the pennywhistle while the rest of the birds learn flugelhorn. Your one talent, provided you're male, involves puffing yourself up the pigeon equivalent of tousling your hair and chasing females around on the sidewalk. Can't imagine why the ladies wouldn't swoon at that move.
But according to a new paper published in the journal Science, the pigeon rep may have just improved considerably. This most proletarian of birds apparently knows how to count.
Plenty of animals, including honeybees, have been shown to have a rudimentary ability to recognize numerosity: distinguishing between two groups of objects when one contains a smaller number of items and the other contains a larger number. But taking the next conceptual step putting three or more groups in sequence from lowest to highest is well beyond them. Only if you can make that intuitive leap can you truly be said to be performing simple math. In a landmark study in 1998, a team of researchers led by cognitive neuroscientist Elizabeth Brannon of Duke University found that rhesus monkeys could be taught just such arithmetical reasoning. This year, another group, led by comparative psychologist Damian Scarf of the University of Otago in Dunedin, N.Z., decided to see if pigeons could be just as mathematically adept.
Looking for signs of higher intelligence in birds is not the fool's errand it once seemed. In recent years, all manner of bird species have been shown to be capable of all manner of cognitive feats from the Caledonian crows that can fashion tools out of bent paper clips to the rooks (another species of crow) that can drop stones in a jar in order to raise the level of water and snatch a floating treat to the blue jays that are savvy enough to hide food in one place when other birds are watching and then hide it somewhere else when the onlookers are gone.
Scarf and his colleagues began their search for mathematical ability in pigeons by training subject birds to recognize groups of one, two or three objects on a screen and peck at them in proper numerical sequence. This, admittedly, was not an easy lesson to get across. It took about a year of practice and rewards before the pigeons could be said with certainty to have gotten the idea. The birds may have actually understood earlier, but the researchers had to make sure they were indeed responding to the number of items, as opposed to their color, shape or relative size. As a result, the pigeons had to be trained with random selections of ovals, triangles, rectangles and even computer clip art before it was clear they had their counting skills down cold.
Even that, however, wasn't enough to put the birds in the same math class as the monkeys. What they'd have to do next was apply the rule they'd learned with the numbers one, two and three to larger, novel numbers they hadn't encountered before. To test that ability, the investigators exposed the pigeons not to three groups of shapes at a time but to just two, and the numbers of objects in each changed continuously. Sometimes the birds were shown pairs of groups containing two familiar quantities (one to three); other times they were shown groups containing two novel ones (four to nine objects); other times they were shown a mixed pair of familiar and novel. In all three cases, they were able to peck the groups in the correct ascending sequence, repeatedly performing above mere chance.
What's more, the pigeons, like the monkeys, consistently performed better when the difference between the numbers of objects in the two groups was wider (two and eight, for example) and worse when it was narrower (five and six, say). This is the same as saying they did better on the easier questions than on the harder ones, which is pretty much what you can say about all of us when we learn a new skill. The striking thing was that the birds did learn.
"I thought it was amazing that monkeys could do this," Brannon, the leader of the rhesus study, told Science, "so we should be even more impressed that pigeons can too."
O.K., none of this is exactly calculus, and human beings can be pretty confident that their spot atop the math ladder is secure. But the new findings are one more sign that other animals do occupy their own, often impressive rungs and that the gap between us and them is getting narrower all the time.