Reinforcement Concordance Induces and Maintains Stimulus Associations in Pigeons

In a first experiment. pigeons were trained to discriminate two pairs of simultaneously presented stimuli. A+ C− and B+ D−. Both pairs were successively and repeatedly presented in every session. After the birds learned the two discriminations, both tasks were synchronously reversed (i.e., A− C+ and B− D+) several times. When reversal performance had stabilized, test reversal sessions were run in which one discrimination (the “leader” task, e.g., A+ C−) was presented for several trials before the second one (the “trailer” task, e.g., B+ C−) was introduced. The animals acquired the trailing task somewhat faster than the leading task, suggesting that associations A ↔ B and C ↔ D that had built up between the stimuli forming the two discrimination pairs were supporting a reversal transfer. A second experiment showed that further reversal experience with a discrimination where the constituent stimuli were presented compounded (AB+Cd− or Ab−Cd+) as well as singly, enhanced the transfer between leading and trailing tasks in subsequent test sessions. A third experiment showed that the same pigeons learned half reversals involving only one discrimination (for example by switching from A+ B−, C+ D− to A− B+, C+ D−) more slowly than full reversals involving both discriminations. These results support the hypothesis that pigeons can associate stimuli that have concordant reinforcement histories. When a reinforcement allocation change causes a change in responding to one stimulus of such an association, pigeons tend to generalize that response change to the other stimulus.