Pigeons may be smarter than we think
Being a "bird brain" may not be all bad. Pigeons, those humble city nuisances, appear capable of previously unrecognized feats of memory and reasoning, according to two new studies out of Tufts University.
The studies, published in the Nov. 8 Proceedings of the National Academies and an upcoming issue of Psychonomics Bulletin and Review, show that the birds can remember large numbers of pictures and recognize relationships among groups of images.
The findings broaden our understanding of thinking in small birds like pigeons and may shed light on human intelligence. "What we describe as complex reasoning ability may be based, at least in part, on cognitive abilities" that humans have in common with pigeons, said Michael F. Brown, a psychologist at Villanova University.
In the first study, pigeons were able to remember up to 1,200 images such as landscapes, cars, or people simultaneously. If trained that a picture of a red
That's the largest memory bank ever proven for birds, said Robert G. Cook of Tufts, a study coauthor. "Pigeons are no slouches. Remembering 1,000 items is a pretty amazing thing."
The pigeons' memories were still outstripped by those of primates, according to the study, which also sought to compare primate and avian intelligence. Coauthor Joël Fagot of the Mediterranean Institute of Cognitive Neurosciences in Marseille tested two baboons, which, after training, demonstrated repertoires of 5,000 images or more.
Both the pigeons and the baboons dealt with their differently sized memory banks in surprisingly similar ways. Both species remembered images best when they'd learned them either early or late in their training. They also responded faster to an image when they remembered it than when they didn't, and they forgot old images at about the same rate.
These patterns of remembering mimic human memory, said psychologist Edward A. Wasserman of the University of Iowa, who was not involved in the PNAS work but collaborated with Cook on the second study. The similarity could allow researchers to use the animals as models when studying human cognition or memory disorders.
"This is a profound resemblance," Wasserman said. "The pigeons and the baboons seem to be performing the task in much the same way as people."
The pigeons' small brains probably limit their capacity to remember images, Cook noted, whereas the baboons hadn't reached their memory limit even after three years of training and testing.
Cook suggested that the need to retain memory -- rather than higher orders of thinking -- might be the driver of animal brain size.
The pigeons' ability to remember so many images "is rather spectacular," said Thomas Zentall, a psychologist at the University of Kentucky, who was not involved in the work. "It probably suggests that humans are able to remember a tremendous amount more than we know or think we can."
The birds showed an even more surprising ability in the second study, Wasserman said: Making comparisons.
The pigeons first viewed a page of 16 small pictures that were either all the same or all different. If the first page showed 16 small identical mugs, for example, the birds were then able to successfully choose a page showing 16 identical hourglasses over a page showing a variety of pictures. They could also identify pages of all-different pictures.
The birds thus showed an ability to compare two relationships -- such as sameness or difference -- rather than just two pictures.
This ability, previously known only in humans and primates, marks a primitive form of thinking using analogies, researchers said.
Roger Thompson of Franklin and Marshall College, who studies primate cognition, called the finding "important" but said he's not yet convinced that the birds use such analogic thinking.
Thompson said the birds may just be recognizing the presence or lack or widespread variability. He said to be convinced, he'd need to see the birds recognize relationships among fewer items, such as two at a time. However, he said, "this is a great demonstration that the animals are making a very abstract discrimination."
In both the new studies, researchers noted, the birds performed tasks while in the unnatural setting of a laboratory. When faced with tasks in their natural habitat, birds may demonstrate even more prodigious capabilities.
For instance, a type of mid-sized bird called the Clark's nutcracker, common in Western states, stashes thousands of pine nuts for winter. Models suggest they may remember up to 5,000 cache sites, Wasserman said.
"We always gain increasing respect for the animals . . . when we see that their capacities are far more advanced than people have given them credit for," he said.
