Associative mediational processes in the acquired equivalence and distinctiveness of cues

Three experiments used rats to examine the acquired equivalence or distinctiveness of cues occurring when 2 auditory and 2 visual stimuli were associated with either the same or with different reinforcing outcomes ([A.sub.1]+, [A.sub.2]+, [V.sub.1]*, and [V.sub.2]* vs. [A.sub.1]+, [A.sub.2]*, [V.sub.1]+, and [V.sub.2]*). Subsequent single modality discrimination learning (e.g., [A.sub.1]+, [A.sub.2]-) was assessed in Experiment 1, whereas in Experiment 2, visual and auditory discriminations were tested concurrently (i.e., {A.sub.1] +, [A.sub.2]-, [V.sub.1]-, [V.sub.2]*). In Experiment 3, auditory and visual discriminations ([A.sub.1] +, [A.sub.2]-, [V.sub.1]-, [V.sub.2]*) were trained and then reversed, using either the same ([A.sub.1]-, [A.sub.2] +, [V.sub.1]*, [V.sub.2]-) or different outcomes ([A.sub.1]-, [A.sub.2]*, [V.sub.1]+, [V.sub.2]-) within each stimulus modality. Discriminations were learned more rapidly in these studies when different outcomes were associated with stimuli from the same modality. These results challenge associative mediational theories of acquired equivalence and distinctiveness.