STIMULUS COMPETITION IN THE ABSENCE OF COMPOUND CONDITIONING

Most associative theories have assumed that stimulus competition occur s only between conditioned stimuli (CSs) that are trained in compound. The present research investigated the possibility of competition betw een two CSs that were individually paired to the same unconditioned st imulus (US). We used human subjects in an anticipatory suppression ana logue to Pavlovian conditioning. Experiment 1 showed that X+ training followed by A+ training resulted in impaired responding to X. This did not occur when hf training preceded X+ training. Experiment 2 replica ted the basic effect and showed that it did not occur when the Phase 2 training consisted of A- instead of A+ nor when the A+ pairings occur red in a second context. Experiment 3 showed that A+ pairings occurrin g in a second context could still produce the effect when X was tested in the context in which the Af pairings had occurred, but not when X was tested in a context different from that used for A+ training. Coll ectively, these results suggest that individually trained CSs may comp ete with each other when one of those CSs is more strongly activated b y the test context than the other one.