Which birds were trained to distinguish Monet paintings from Picasso paintings in a 1995 experiment? Pigeons. Researchers trained pigeons to peck at Picasso paintings while withholding the response for Monet paintings, then tested whether the birds could classify unfamiliar works.
The pigeons eventually generalized beyond the paintings used during training. They distinguished the artists' styles even when shown new examples, and their performance reflected the broad difference between Picasso's cubism and Monet's impressionism. When Monet paintings were shown upside down, however, the birds' categorization became less reliable, suggesting that image orientation mattered.
The experiment did not show that pigeons understood art history or appreciated artistic style as humans do. It showed that they could learn visual categories from complex images. The study, by Watanabe, Sakamoto, and Wakita, became famous partly because the authors received the 1995 Ig Nobel Prize in psychology. Later work also compared pigeon and human performance on other painter-classification tasks.