Preception in the rat: autonomic response to shock as function of length of warning interval.

The autonomic response (galvanic skin response) to a noxious stimulus (shock) is reduced when the stimulus is preceded by a warning signal. The greatest reduction, 53 percent, was obtained with a warning interval of 1 second. Warning also reduces variance of the response over trials, a decrease of over 90 percent for the optimum 1-second interval.