Researchers have found that pigeons can use orthographic processing to discriminate between words and non-words. The birds were capable of more than just memorization; they could still recognize words as real even if they hadn’t seen the words previously. The details are in a paper that was just published in the journal Proceedings of the National Academy of Sciences.
Orthographic processing helps with the formation of visual memories and aids in recognizing and reading words. The ability is not believed to be specific to animal species that use language. Instead, orthographic processing is thought to use the same visual circuits that allow animals to recognize objects in their environment. To test this theory, researchers from the University of Otago and Ruhr University used domestic pigeons.
A group of 18 pigeons were trained to tell the difference between actual words and non-words that consisted of four random letters. If a real English word appeared on the screen, the pigeons were supposed to peck at the word. If a non-word appeared, the pigeons were trained to peck a star symbol. The birds developed vocabularies containing at least 20 words and up to 56 words. By this point, the pigeons had also seen thousands of non-words. The training took 8 months and birds that performed poorly were excluded from the final trials.
The pigeons consistently identified real words and differentiated them from non-words. To control for simple memorization, the research team showed them new words that they had never seen before. The birds were able to distinguish these new words from non-words at a rate comparable with previous baboon studies. The team believes that the pigeons were using bigrams, sets of two letters that hint at a word being real or fake. For example, the bigram “EN” is more common in real words than “PT”.
Previously, only primates had been tested in word recognition trials. The pigeons in this study performed just as well as baboons, showing that orthographic processing can occur in animals that lack language skills. The findings provide new insights into the evolution and processing of words and language.
Damian Scarf et al. Orthographic processing in pigeons (Columba livia). Proceedings of the National Academy of Sciences (2016).