Amplitude and Habituation of the Orienting Reflex as a Function of Stimulus Intensity

Abstract

ABSTRACT Two within‐ S experiments involving 20 S s each and one between‐ S experiment employing 100 S s were performed to examine effects of stimulus intensity on orienting response amplitude and habituation. Five intensities of a 1000 Hz tone were presented, ranging from 0 to 40 dB in Experiment I and from 0 to 80 dB in Experiments II and III. Response measures were skin conductance response (SCR) and heart rate (HR). Skin conductance response amplitude increased monotonically with stimulus intensity while HR deceleration was a generally decreasing function which tended to decrease, increase, and finally decrease again as intensity increased. Not only was deceleration greatest at 0 dB but it was more resistant to habituation. Several intensities of test stimulation were presented after habituating stimuli in the between‐ S experiment. Skin conductance response to test stimuli was facilitated by habituation at 0 dB and depressed by habituation at 80 dB. The results suggest a direct relationship between stimulus intensity and development of habituation.