Conditional discrimination learning of two-object-pairs by rats

Two rats were trained in a successive same/different discrimination task, where pairs of simultaneously presented objects were used as discriminative cues for conditional place discrimination. Depending on the same or different relationship between the two objects in a pair, responses to the right or left alley were differentially reinforced. In the rst acquisition phase, responses to a task of AA/BB vs. AB/BA did not exceed chance. To make the task easier, pair BB was withdrawn in Phase 2 (AA vs. AB/BA), and, as a result, both rats achieved learning criterion. Rat 1 also reliably learned the Phase 3 task, where pair BB was reintroduced (AA/BB vs. AB/BA). Although Rat 1 learned the Phase 3 task, where a single item feature could not be an effective discriminative cue, the data suggest that rats learn some item-speci c con gural information for item pairs. Given that the experimental method of the present study achieved basic discrimination learning of object pairs by rats, it may be suitable for a S/D discrimination learning experiment using object pairs. Factors that may facilitate relational learning in rats are discussed