Stimulus-reinforcer interactions in Pavlovian conditioning of pigeons: Implications for selective associations

In a Pavlovian procedure, groups of pigeons were presented with a compound auditory-visual stimulus that terminated with either response-independent electric shock or food. In a subsequent test, the tone CS was dominant in aversive conditioning, reliably eliciting conditioned head raising and prancing. The red light CS was dominant in appetitive conditioning, reliably eliciting pecking. This result was replicated in a second experiment, in which trials were widely spaced. Pour additional groups of pigeons received pairings of the separate element CSs with the USs. Red light, but not tone, was an effective CS in appetitive conditioning, whereas tone, but not red light, was effective in aversive conditioning. There was no discriminative responding in zero-contingency control groups. Several theoretical accounts of these data are discussed.