“TRANSITIVE INFERENCE” IN MULTIPLE CONDITIONAL DISCRIMINATIONS

We used multiple conditional discriminations to study the inferential abilities of pigeons. Using a five‐term stimulus series, pigeons were trained to respond differentially to four overlapping pairs of concurrently presented stimuli: A+B−, B+C−, C+D−, and D+E−, where plus and minus indicate the stimulus associated with reinforcement and extinction, respectively. Transitive inference in such situations has been defined as a preference for Stimulus B over Stimulus D in a transfer test. We measured this and other untrained preferences (A vs. C, A vs. D, B vs. E, etc.) during nonreinforced test trials. In three experiments using a novel, rapid training procedure (termed autorun ), we attempted to identify the necessary and sufficient conditions for transitive inference. We used two versions of autorun: response‐based, in which the subject was repeatedly presented with the least well‐discriminated stimulus pair; and time‐based, in which the subject was repeatedly presented with the least‐experienced stimulus pair. In Experiment 1, using response‐based autorun, we showed that subjects learned the four stimulus pairs faster than, but at a level comparable to, a previous study on transitive inference in pigeons (Fersen, Wynne, Delius, & Staddon, 1991), but our animals failed to show transitive inference. Experiments 2 and 3 compared time‐ and response‐based autorun. Discrimination performance was maintained, but transitive inference was observed only on the second exposure to the response‐based procedure. These results show that inferential behavior in pigeons is not a reliable concomitant of good performance on a series of overlapping discriminations. The necessary and sufficient conditions for transitive inference in pigeons remain to be fully defined.