Avian art critics
In 1995, a team of researchers at Japan's Keio University led by psychologist Shigeru Watanabe demonstrated that common pigeons (Columba livia) can learn to classify complex works of art. The experiment trained pigeons to discriminate between paintings by Claude Monet and Pablo Picasso. The birds were divided into two groups. One group was rewarded with food for pecking a button when shown a slide of a Monet painting, but received no reward for a Picasso. The second group was rewarded for pecking only at the Picasso paintings.
The initial training used ten paintings from each artist. By the 20th day of the experiment, the pigeons could correctly identify the target artist with a high degree of accuracy. The study employed operant conditioning, a method of learning that uses rewards and punishments for behavior. This experiment showed that the pigeons' behavior could be controlled by complex visual stimuli in a way that suggests categorization. The pigeons were more than memorizing the ten specific images they were trained on. They were learning to recognize the defining visual characteristics of Impressionism and Cubism.
Generalizing artistic styles
The most remarkable part of the study came next. Researchers showed the trained pigeons paintings by Monet and Picasso that they had never seen before. The birds successfully categorized these new paintings, proving they had learned the general artistic style, rather than a set of specific images. Their ability to generalize went even further. The pigeons grouped paintings by Impressionists like Cézanne and Renoir with Monet's work. They also correctly associated works by Cubists like Braque and Matisse with Picasso's paintings.
To understand what visual information the pigeons were using, the scientists ran more tests. They presented the paintings in black and white, upside down, and partially covered. Removing color cues by showing black-and-white images decreased their discrimination performance, indicating that color is one of the cues they use. Turning Monet's paintings upside down confused the pigeons, but inverting Picasso's work did not affect their accuracy. This suggests the pigeons recognized the realistic objects and scenes in the Impressionist paintings, and their inversion made them unfamiliar. The abstract nature of Picasso's Cubist works meant that orientation was not a critical feature for identification. The research, which earned the team a 1995 Ig Nobel Prize in Psychology, shows the visual processing and cognitive abilities of non-human animals.