Pigeon Perception of Letters of the Alphabet

In a three-choice discrimination task three pigeons learned to distinguish each letter of the alphabet from all other letters. Errors during learning were based on 54 presentations of each target letter with every other letter. The errors were used to scale letters in a multidimensional similarity space and to associate them in hierarchical clusters. The results resembled those generated from similarity judgments by humans, suggesting cross-task and cross-species generality in processes of letter discrimination.