What is learned when concept learning fails?—A theory of restricted-domain relational learning

Two matching-to-sample (MTS) and four same/different (S/D) experiments employed tests to distinguish between item-specific learning and relational learning. One MTS experiment showed item-specific learning when concept learning failed (i.e., no novel-stimulus transfer). Another MTS experiment showed item-specific learning when pigeons’ novel-stimulus transfer decreased because they chose familiar training comparisons instead of matching novel comparisons. In 8-item and 3-item S/D tasks, pigeons and monkeys were accurate with unfamiliar training-stimulus pairings, stimulus inversions, and distorted stimuli, suggesting relational learning within a domain restricted to the training stimuli (i.e., no novel-stimulus transfer). In 32-item S/D tasks, pigeons with previous 8-item training showed less transfer than those without prior training, suggesting a carryover of restricted-domain relational learning. Pigeons shifted from 1024-item to 8-item S/D tasks showed reinstatement of restricted-domain relational learning. These findings are important in specifying which types of learning occur in these tasks, showing that subjects failing novel-stimulus transfer are not required to switch from item-specific to relational learning as a training set is expanded, and demonstrating that concept learning failure is not proof of item-specific learning.