Abstract
This experiment examines whether the relational responses of pigeons are controlled by the relations between stimuli on a relative numerosity discrimination, using multiple-pair discrimination training. In the discrimination training, three birds discriminated two pairs of number stimuli (1-3, 5-7). For two birds, the responses to smaller arrays were reinforced, and for the remaining bird, the responses to larger arrays were reinforced. After the birds learned to discriminate numerosity stimuli, a test was conducted, in which four test pairs (1-5, 3-7, 2-6, 2-5 or 3-6) were presented. Three of the four test pairs were combinations of stimuli with the same reinforcement history (S+-S+, S--S-, novel-novel), and one test pair was a combination of a stimulus with S+ history and a novel stimulus. The results of the tests showed that all the birds mostly demonstrated relational responses. Although the possibility still remains that other factors might affect the responses of the birds, the results provided evidence that the performances of the birds are mainly controlled by the relations between stimuli.
