Learning and transfer of relational matching-to-sample by pigeons.

We trained pigeons on a relational matching-to-sample task to see whether a nonprimate species can discriminate higher-order "relations between relations". W e required the birds t o relationally match arrays of 1 6 itemsthat were chosen from five nonoverlapping sets of 20 colored computer icons. On each trial, randomly selected icons from one set were placed into a 4 x 4 grid to form a sample; on same trials, all 16 icons were identical to each other, whereas on different trials, all 16 icons were different from each other. After 10-20 pecks, 16-item same and different testing arrays were presented that were created from a nentirely different icon set. Because noicons were common to the sample and testing arrays, discriminating higher-order relations was required for success on the tests. As have primates in similar tasks, pigeons successfully learned and transferred this relational discrimination, suggesting that both birds and mammals possess t he cognitive antecedents of analogicalreasoning.