The common pigeon has been tapped to guide missiles and spot life rafts, but it has never undertaken the role of the radiologist. Until now.
In a study released last week, scientists at UC Davis and two other institutions examined whether pigeons with their visual prowess could perform the daunting task of accurately identifying cancerous masses in tissue slides and mammograms. In some cases, they could, according to the study, which appeared in the journal PLOS ONE.
In particular, pigeons could be trained to identify malignant or benign objects in tissue slides they had never seen before, the unprecedented finding revealed. That result helps shed light on the similarities between humans and pigeons in the way they perceive objects.
Making use during World War II of pigeons’ distinct visual identification skills, behavioral psychologist B.F. Skinner divided a missile nose cone into three compartments and strapped a pigeon into each – with the birds steering the bomb by pecking on-screen images that showed a target they had been trained to recognize.
In the 1970s and 1980s, the U.S. Coast Guard used pigeons in Project Sea Hunt, in which the birds were trained to accurately spot orange objects at sea, with the goal of finding floating survivors and equipment.
That success suggested pigeons could be trained to read breast cancer images, said Richard Levenson, professor of pathology and laboratory medicine at UC Davis Health System and lead author of the study.
The information gleaned from the study may prove a benefit to physicians when identifying cancerous masses, he said.
“The study worked tremendously well. The pigeons were able to master the pathology problem we posed them,” Levenson said. “They not only did it successfully, they did it quickly.”
The researchers, who also worked at the University of Iowa and Emory University, placed the pigeons in a light box where they were first shown slides of breast tissue.
In the first experiment, eight pigeons were shown 144 breast tissue images at different magnifications and awarded with a food pellet if they pecked areas of the image with cancerous tissue. After 15 days of training, the pigeons achieved an 85 percent accuracy rate identifying malignant or benign objects, Levenson said.
Then the pigeons were shown slides they had not seen before. In that task the birds accurately identified malignant or nonmalignant tissue 77 percent of the time, a finding that established the birds were not acting by rote but had in fact learned to find images of malignant tissue in the slides.
“They’re kind of like humans in that they are plastic – they can change and adapt,” Levenson said.
In another experiment, four pigeons were able to identify microcalcifications in breast tissue slides – also to 85 percent accuracy after training.
The third experiment proved more challenging. The birds were put in the tricky role of identifying masses in 40 cropped mammogram images – a daunting task, even for a trained radiologist. Such masses are much less defined and reading the mass edges demands making sense of visual complexities.
“These images have a lot to do with the edges of masses and how irregular they are, as well as the density of the masses,” said Edward Wasserman, professor of experimental psychology at the University of Iowa and co-author of the study.
After training, the pigeons were able to identify masses in images they had seen before to an accuracy rate of 80 percent. But when they were shown new mammogram images, they couldn’t identify masses with any accuracy.
“Identifying that is really tough to do. This is why people spend years perfecting the skill,” Wasserman said.
It remains to be seen how valuable the study will be to physicians and their perception of objects, but some see the study as promising.
“When humans see stimuli, our vision tends to ignore small details and tries to find overall meaning,” said Toru Shimizu, a psychology professor at the University of South Florida who was not involved in the study. “That is useful most of the time, as we can recognize whole objects and faces easily without getting distracted by tiny details like scratches or shades.”
However, that can be a problem when detecting minuscule cancerlike cells in pathological or radiological images, he said.
“Pigeons are different. They’re extremely good at detecting local details and ignoring global meaning,” Shimizu said.
Edward Ortiz: 916-321-1071, @edwardortiz