Pigeons (Columba livia), which are characterized by their blue-gray feathers and dark black markings, are a common sight in most big cities. While the birds have a brain no larger than the tip of an index finger, studies indicate they have a tremendous capacity to discriminate and categorize a wide range of objects and images. Now researchers from the University of California, Davis, and the University of Iowa (UI) have found that these birds can even distinguish between benign and malignant human breast tissue in digitized mammogram slides. 

"These results go a long way toward establishing a profound link between humans and our animal kin," Edward Wasserman, co-author and a professor of psychological and brain sciences at the UI, said in a news release. "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."

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While it took some training and selective food reinforcement, the pigeons quickly learned to correctly identify digitized slides and mammograms of benign and malignant human breast tissue, even when presented with varying slides. Researchers explained the birds' accuracy was most affected by the presence or absence of certain colors in the images, as well as by image compression. The same is true of human doctors. However, the birds did have a tougher time classifying abnormal masses on mammograms, but were able to identify cancer-relevant micro calcifications.

"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," Richard Levenson, professor of pathology and laboratory medicine at UC Davis, added. "Pigeons' accuracy from day one of training at low magnification increased from 50 percent correct to nearly 85 percent correct at days 13 to 15."

Their findings, recently published in the journal PLOS ONE, shed light on how physicians process visual cues of slides and X-rays and suggest the pigeon's remarkable abilities could be used to explore image quality and enhance diagnostic performance.

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