Give the pigeon credit for work that could explain our evolution
by Helene Ragovin

“If any one faculty of our nature may be called more wonderful than the rest, I do think it is memory,” the British novelist Jane Austen wrote. “There seems something more speakingly incomprehensible in the powers, the failures, the inequalities of memory, than in any other of our intelligences.”

Robert Cook and one of his brainy birds © ZARA TZANEV

This fascination with the nature of memory is, of course, not limited to writers or philosophers. Scientists, too, have sought to unravel the secrets of memory. In examining the long-term memory capacity of birds and baboons, a Tufts psychologist hopes to yield clues to the course of human evolution and the workings of our own brains, and contribute to our understanding of neurodegenerative diseases like Alzheimer’s.

“This will be pretty exciting over the next couple of decades,” said Robert Cook, professor of psychology.

Cook and a French colleague, Joel Fagot, worked with pigeons and baboons, showing the animals thousands of color photographs on a computer screen and then testing to see if they remembered them. The first time the animals were shown a specific image, they were taught to associate it with either a “right” or a “left” response—the pigeons by touching a screen with their beaks; the baboons by pointing a joystick. The right or left responses were randomly assigned to the images.

The pigeons and baboons were shown the images repeatedly over a three- to five-year period, and the researchers recorded whether the animals responded by touching or pointing in the proper direction.

Even after factoring in the possibility for “guesses,” it was apparent that both the pigeons and baboons were able to recall a significant number of images: between 800 and 1,200 for the pigeons (65 percent), and between 3,500 and 5,000 for the baboons (70 percent). The researchers also believe the baboons had not reached their memory capacity, even after three years of the study, and could likely have remembered more—possibly as many as 14,000 images—if the study had continued. (While comparable work has not been done on humans because of the duration of such a study, Cook said people are able to remember at least tens of thousands of images.) Cook and Fagot published their findings in November in Proceedings of the National Academy of Sciences.

No bird brains here
“The one big difference [between the pigeons and the baboons] was the capacity of the two species,” Cook said. “The baboons could remember four to five times more information [during the course of the experiment]—not that the pigeons were any slouches.” While baboons have a greater brain size relative to their body mass than pigeons do—thus, it was expected that the monkeys would be able to remember more images—“it’s remarkable that the birds could remember so much with so little” brain size, Cook said.

And, the pigeons and baboons showed similar patterns in their results, retaining the earliest and latest images most often. “This suggests memory was expressing in much the same way,” Cook said, “but the baboons had larger ‘hard drives,’ ”—more capacity for storing information.

These results suggest that the expansion of long-term memory capacity may have played an important role in the evolution of cognition and behavior among animals and humans, Cook said. “Many factors have been suggested to account for the advanced intelligence of humans,” Cook said. “Our comparison of monkey and bird memory suggests that the expansion of memory may have been one of those factors. Our ancestors long ago may have first started to remember information in great detail before they started to think about the abstract meaning of that information.”

The human mind appears to remember things in two different ways, Cook said, first, by recalling specific, concrete pieces of information and, later, by remembering overarching principles and concepts that incorporate those specifics.

Mind mapping
He compared the two to the experience of learning your way around a new city. “First, you travel from point to point, but then you develop a cognitive map and start navigating more conceptually,” he said. “It’s the memory of a specific fact, versus the amount of time to turn that specific into abstract concepts.” An area for future research, he said, is looking at the “cognitive interplay between item memorization and concept learning” in animals.

“This opens up the possibility of developing an animal model for looking at long-term memory decline and how we might come up with treatments for that kind of decline,” he said. “Birds don’t age nearly as long as humans, so there is the possibility of studying changes in long-term memory within a feasible lifetime” of a pigeon or other bird. That work, in turn, could help in the development of treatments that might alleviate the declines in memory that occur with diseases such as Alzheimer’s or even from simple cognitive aging.

Helene Ragovin is a senior writer in Tufts’ Office of Publications. She can be reached at helene.ragovin@tufts.edu.