Formation of tone-US associations does not interfere with the formation of context-US associations in pigeons

In four experiments we investigated whether signaled and unsignaled US presentations resulted in differential context conditioning. Experiments 1 and 2 showed that the presence of a tone during grain presentation facilitated the formation of tone-food associations in pigeons. Experiment 2 also showed that the acquisition of associative value by the tone did not diminish associations between context and the unconditioned stimulus (US). Experiment 3 showed that signaled USs did not interfere with the acquisition of context-US associations, and Experiment 4 showed that even when the signal was extensively pretrained, context-US associations could not be blocked. The results of these experiments are inconsistent with conditioning models that require competition between cues and contexts for associative value.