Apparatus exposure produces profound declines in conditioned nictitating-membrane responses to discrete conditioned stimuli by the rabbit (Oryctolagus cuniculus)

The present experiments demonstrated that in the rabbit (Oryctolagus cuniculus) nictitating-membrane (NM) preparation, exposure to the experimental apparatus produces profound declines in conditioned responding to a discrete conditioned stimulus (CS; Experiments 1, 2A, and 3). Moreover, this decremental effect is at most attenuated in only a minor way when the unconditioned stimulus (US) is presented during exposure to the apparatus (Experiment 2B). Controls for retention loss (Experiments 1 and 3) and for handling and placement in a different context (Experiment 3) did not produce significant declines in responding. These findings challenge theories of extinction that rely primarily on context-US associations but are more consistent with theories that assume context-CS-US associations.