If pigeons went to medical school and specialized in pathology or radiology, they would be pretty good at distinguishing normal breast tissue from cancerous breast tissue on digitized microscope slides and mammograms, according to a new study published in PLOS One (2015; doi:10.1371/journal.pone.0141357).

With some training and selective food reinforcement, pigeons performed as well as humans in categorizing digitized slides and mammograms showing benign and malignant human breast tissue, the researchers found. The pigeons were able to generalize what they had learned, so when shown a completely new set of digitized slides of normal and cancerous tissue, they correctly identified them.

Their accuracy, like that of humans, was modestly affected by the presence or absence of color in the images, as well as by degrees of image compression. The pigeons also learned to correctly identify cancer-relevant micro calcifications on mammograms, but they had a tougher time classifying suspicious masses on mammograms, which is a task considered difficult even for skilled human observers.

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“These results go a long way toward establishing a profound link between humans and our animal kin,” said coauthor Edward Wasserman, PhD, professor of psychological and brain sciences at the University of Iowa in Iowa City. “Even distant relatives, like people and pigeons, are adept at perceiving and categorizing the complex visual patterns that are presented in pathology and radiology images, surely a task for which nature has not specifically prepared us.”

The pigeons’ successes and difficulties provide a window into how physicians process visual cues present on slides and radiographs to diagnose and classify disease risk. This work also suggests that pigeons’ remarkable ability to discriminate between complex visual images could be put to good use as trained medical image observers, to help researchers explore image quality and the impact of color, contrast, brightness, and image compression artifacts on diagnostic performance.

Although the brain of a pigeon is no bigger than the tip of an index finger, the neural pathways involved, including the basal ganglia and cortical-striatal synapses, operate in ways very similar to those at work in the human brain.

Wasserman explains that the common pigeon (Columba livia) has a tremendous capacity to discriminate and categorize a wide range of objects and images.

“Research over the past 50 years has shown that pigeons can distinguish identities and emotional expressions on human faces, letters of the alphabet, misshapen pharmaceutical capsules, and even paintings by Monet vs. Picasso,” Wasserman said. “Their visual memory is equally impressive, with a proven recall of more than 1800 images.”

“The birds were remarkably adept at discriminating between benign and malignant breast cancer slides at all magnifications, a task that can perplex inexperienced human observers, who typically require considerable training to attain mastery,” said coauthor Richard Levenson, MD, FCAP, professor of pathology and laboratory medicine at University of California Davis Health System. “Pigeons’ accuracy from day 1 of training at low magnification increased from 50% correct to nearly 85% correct at days 13 to 15.”

Levenson envisions pigeons providing reliable feedback to validate new technologies in pathology.