Pigeons may be ubiquitous, but they're also brainy, according to a new study that found these birds are on par with primates when it comes to numerical competence.
The study, published in the latest issue of the journal Science, discovered that pigeons can discriminate against different amounts of number-like objects, order pairs, and learn abstract mathematical rules. Aside from humans, only rhesus monkeys have exhibited equivalent skills.
Could pigeons then be the Einsteins of the bird world?
"It would be fair to say that, even among birds, pigeons are not thought to be the sharpest crayon in the box," lead author Damian Scarf told Discovery News. "I think that this ability may be widespread among birds. There is already clear evidence that it is widespread among primates."
Scarf, a postdoctoral researcher in the Department of Psychology at the University of Otago, and colleagues Harlene Hayne and Michael Colombo began the study by first teaching pigeons how to order the numbers 1, 2 and 3.
To do this, they presented the pigeons with three images containing one, two, or three objects. All three images appeared at once on a touch screen and the pigeons pecked the screen to make a response. If they correctly accomplished the task -- pecking the images in ascending order -- they received a wheat snack.
"We took steps to ensure things like volume could not control responding in training and testing," he said. "For example, during training and testing, the higher numerosity did not always have the largest surface area/volume and thus the pigeons could not respond based on this stimulus dimension."
The images also came in different colors and shapes, so the pigeons weren't somehow linking those qualities to quantity.
Next, the researchers upped the ante, to see whether or not pigeons had just learned to order 1, 2, and 3, or if they'd learned a more abstract rule. Scarf and his team presented the pigeons with pairs of images containing 1, 2, 3, 4, 5, 6, 7, 8, or 9 objects. The pigeons again had to pair the items in ascending order. For example, if a pigeon saw 8 and 5, it had to peck the objects representing 5 first.
"Remarkably, the pigeons were able to respond to these novel pairs correctly," Scarf said. "In addition, their performance was indistinguishable from that of two rhesus monkeys that had been previously trained on this task."
For a while, scientists have suspected that birds were math whizzes. Prior studies, however, usually focused on very socialized individuals like Alex, an African grey parrot that belonged to Irene Pepperberg, an adjunct professor of psychology at Brandeis University and a lecturer at Harvard.
Alex, who died suddenly in 2007, could count and talk and had the intelligence of a 5-year-old human and the emotional maturity of a 2-year-old, according to Pepperberg.
Parrots are often just given credit for mimicking humans when they talk, but Pepperberg told Discovery News that Alex created new word labels for objects by combining words he already knew.
For example, he called a juicy red apple that appears to have brought to mind bananas and cherries a "banerry."
In terms of math, one of Alex's greatest feats was that he understood a numerical concept akin to zero, which is an abstract notion that people don't typically understand until age three or four.
Now scientists are facing a parrot/pigeon/primate puzzle. Why is it that birds and primates seem to share math skills?
One explanation could be that the last common ancestor of these two groups possessed amazing numerical competence, but that would mean many other animals have it too, and studies haven't found clear evidence for such abilities yet.
Another possibility is that math skills somehow evolved independently in birds and primates.
"At this point in time, I have no inkling as to which hypothesis is correct," Scarf said. "To answer this question, many distantly related animals would have to be tested."