Associations to contextual stimuli as a determinant of long-term habituation.

A series of experiments was performed to determine whether long-term habituation of the acoustic startle response in rats is mediated by conditioned associations between contextual cues and the test stimulus. Experiment 1 established parameters yielding demonstrable long-term habituation of the startle response. Experiment 2 attempted to overshadow the hypothesized associations to contextual cues by providing a more reliable predictor of the acoustic stimulus. Experiment 3 investigated the effect of changes in contextual cues on long-term habituation. Experiment 4 provided treatments designed to extinguish the hypothesized associations between the context and the habituated stimulus. Experiment 5 sought latent inhibition of the hypothesized association between the contextual cues and the acoustic stimulus. The results of these experiments uniformly failed to support an associative model of long-term habituation of the startle response, but they are consistent with a nonassociative model emphasizing habituation to the entire experimental situation rather than exclusively to the iterated stimulus.