Abstract
The approach-withdrawal behaviour of pigeons to a red keylight was measured under three conditions; a negative contingency (NC) between keylight and food reinforcement, a CI or conditioned inhibition procedure where the keylight was non-reinforced in compound with a tone which was reinforced when presented alone, and a random control procedure (RC). The keylight-food contingencies in CI and NC were identical, and keylight and food presentation frequency were the same in all conditions. Subsequently the effect of adding the red keylight to a novel CS+ during or after excitatory conditioning was examined (summation test of inhibition). The inhibitory procedures, CI and NC, generally yielded similar functions for the acquisition of withdrawal, and the results of the withdrawal and summation measures were positively correlated. The implications of the results for theories of the acquisition and behavioural action of conditioned inhibitors are discussed.