Pigeons can distinguish between healthy and cancerous tissue in x-rays and microscope slides with an accuracy rate of up to 99%, according to a new study in Plos One.

In a series of three experiments, led by Richard Levenson, professor of pathology and laboratory medicine at the University of California Davis Medical Center, it was found that pigeons have the capacity to learn how to identify whether an image shows healthy or cancerous breast tissue. The birds “share many visual system properties with humans”, according to the study.



During the first experiment, eight pigeons were presented with 144 breast tissue images, at various levels of magnification and with and without color. The birds could then peck a blue or yellow button on either side of each image, to indicate whether it was cancerous or healthy.



If they chose correctly, they were rewarded with food but if they chose incorrectly, they were presented with the image again and again until they correctly identified it.

“With some training and selective food reinforcement, pigeons do just as well as humans in categorizing digitized slides and mammograms of benign and malignant human breast tissue,” Levenson told the International Business Times.

After 15 days of training, the birds’ accuracy rate had risen from 50% to 85%. The pigeons were then presented with new images to rule out memorization as a possible cause for their success. They correctly identified the familiar and novel images 87% and 85% of the time.

When researchers combined the birds’ responses, a method they called “flock sourcing”, rather than scoring them individually, they found that their accuracy increased to 99%.

“The pigeons were able to generalize what they had learned, so that when we showed them a completely new set of normal and cancerous digitized slides, they correctly identified them,” Levenson said.



The second experiment was similarly successful. Four new birds were tested to see if they could identify micro-calcifications – calcium deposits that are associated with the presence of cancer – in breast tissue. Within 14 days, their accuracy rate rose from 50% to over 85%.



The final experiment had another four birds attempt to identify masses in mammograms. While the pigeons were able to identify masses in images they had already seen with some success – two pigeons reached 80% correct classification and two reached 60% – they could not identify masses as benign or malignant in new images.

According to the study, this can also be very challenging for humans. A panel of radiologists previously tested reached an 80% accuracy rate when viewing the same images.

“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,” Edward Wasserman, professor of experimental psychology at the University of Iowa and co-author of the study, told the Sacramento Bee. “Identifying that is really tough to do. This is why people spend years perfecting the skill.”

The results suggest that pigeons could be involved in helping researchers and engineers evaluate new medical imaging techniques as they continue to innovate, according to Levenson.

“Pigeons may not be able to write poetry, but they’ve had millions of years to develop the abilities that they need to navigate a very complicated and dangerous world,” Levenson told the Smithsonian magazine. “So it doesn’t surprise me that they can do pathology!”