A pigeon stands in front of a screen, scans an image of breast tissue and assesses whether it's cancerous. While pigeons posing as pathologists may seem far-fetched, it could be the future of nuclear medicine.
"Right now, there are people scanning thousands of images — and determining whether the images tell us something. I think pigeons could easily step in and at least do a first pass," says Richard Levenson, a professor of pathology and laboratory medicine at the University of California Davis.
Levenson was one of the principal researchers in a groundbreaking study testing whether pigeons can detect cancer by looking at tissue samples. As it turns out, they can — and with great accuracy. In fact, researchers behind a joint UC Davis/University of Iowa study discovered that pigeons are often as accurate as radiologists.
During the researchers' two-year study, pigeons were trained to identify cancerous and non-cancerous images using "operant conditioning," a method that rewarded the birds with food each time they correctly identified an image. The birds pecked to one side of an image if they spotted malignant cells, and to the opposite side of an image if they saw only normal cells.
The pigeons — not the first animals recruited in the fight against cancer — learned to recognize benign or malignant tissue samples at a variety of resolutions, ranging from low to high magnification. They also learned to detect cancerous cells in both color and black-and-white images. After two weeks of training, the birds were 85 percent accurate in detecting cancer, but their accuracy declined when presented with particularly novel or dense images. The birds' accuracy mirrored that of human radiologists, most of whom typically reach an accuracy level of about 80 percent.
"The images the birds have trouble with are the ones people have trouble with," says Ed Wasserman, a professor of psychology at the University of Iowa and co-author of the study.
In some cases, the birds' diagnoses were nearly perfect. For example, when four birds were shown a set of high-resolution images, the group's accuracy level reached 99 percent. Researchers called this "flock-sourcing."
The pigeons' near-100 percent accuracy in detecting cancer didn't really surprise Wasserman, he admits. "What was shocking is that they were able to extrapolate it," he says. "We trained pigeons with one set of images, then tested them with another set of images they had never seen before — and the birds transferred their knowledge almost perfectly. They learned to transfer what they had learned to brand new examples. That makes them potentially prodigious diagnosticians."
The key, Wasserman says, lies in the pigeon's brain, which is only about the size of a grape. Despite its diminutive size, a pigeon brain's neural pathways, including the basal ganglia and the cortical-striatal synapses, work in much the same way as ours.
"Previous studies have shown that birds can recognize individual human faces and emotional expressions on those faces, that birds can discriminate between artwork by Monet or Picasso, and that birds can do all kinds of elaborate and exquisite things with their sight," Wasserman says.
These past findings prompted the researchers to probe pigeons' visual skills and apply the birds' prowess to pathology.
"The surprising thing was not that it worked, but that it worked so well, and so quickly," Levenson says, adding that the study information was rejected from three different scientific journals before being published by PLOS ONE.
And while the scientists don't see pigeons as replacements for human diagnosticians, they do suggest we can learn much from the process by which pigeons learn, and better understand ways to correct for human error. Who knows — some time in the near future, "bird brain" may just become a compliment.