The effects of signal value on short- and long-term habituation

The present study examined the effects of signal value on short- and long-term habituation of the skin conductance response. Subjects (N = 48) attended the laboratory at the same time of day on two consecutive days. Day 1 comprised pretraining and training phases, and day 2 comprised the test phase. In the pretraining phase subjects received one presentation each of a tone and a vibration stimulus. In the training and test phases subjects received a randomly ordered sequence of 15 tones and 15 vibrations. All stimuli were of 4 s duration. During the training phase Groups E1 and E2 performed a motor response to the offset of one of the stimuli whereas a third group (Group C) did not. Neither Group E1 nor Group C performed the motor task during the pretraining and test phases. Both between- and within-group analyses of the training phase data indicated that responses were larger and habituation was slower to signal stimuli. Analyses of the test phase data and comparison of pretraining and test phase data indicated that long-term habituation occurred only to nonsignal stimuli. The results are discussed in terms of Wagner's (1978) theory of habituation.