"Pseudoconditioned" jaw movements of the rabbit reflect associations conditioned to contextual background cues.

Two experiments employing 180 rabbits and involving tone conditioned stimuli (CSs) and intraoral water unconditioned stimuli (UCSs) investigated pseudoconditioning of jaw movement. CS-alone, UCS-alone, paired CS-UCS, and four explicitly unpaired CS-UCS treatments were compared to no stimulus presentation. UCS-alone presentations were sufficient to produce pseudo-CR (conditioned response) acquisition. Pseudo-CRs were retained and gradually extinguished over 30 days of CS-alone presentations. Random sequences of unpaired CSc and UCSs produced higher pseudo-CR frequencies than fixed sequences. A pseudo-CR partial reinforcement extinction effect was observed. Background extinction, that is, simply confining the subject in the experimental environment without stimulation, was effective in extinguishing both pseudo-CRs and CRs. Pseudo-CR results could not be attributed to CS-UCS trace conditioning, sensory preconditioning, second-order conditioning, or intra-analyzer conditioning. Results indicate that the associative mechanisms underlying pseudoconditioning phenomena involve conditioning of associations to contextual background (apparatus, trace, temporal, and sequential aftereffect) cues by UCS-alone and unpaired UCS presentations.