Effects of length of training and amount of tone intensity change on amplitude of autonomic components of the orienting response

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Abstract
The present study investigated amplitude of the skin conductance response (SCR), heart rate response (HRR), and digital pulse amplitude (DPA) response components of the orienting response to a change in tone intensity following habituation training. Experimental subjects received either 5 or 20 presentations of a 1000 Hz, 70 dB training stimulus of 3 sec duration followed by presentation of a test stimulus. Half of these subjects received a test stimulus of 63 dB (decrease of 7 dB), while for the other half, the test stimulus was a 56 dB (decrease of 14 dB) tone. Two independent control groups received 6 and 21 presentations of the training stimulus respectively, resulting in a 3 × 2 factorial design (N = 90). The results indicated that test trial SCR amplitude was significantly larger in the 14 dB change groups than in either the 7 dB change groups or the control groups. The 7 dB change groups did not differ significantly from the control groups in terms of test trial SCR amplitude. Experimental groups displayed significantly larger HRRs than did control groups, but within the experimental groups, response amplitude was not influenced by amount of change. For digital vasoconstriction, decrease in stimulus intensity did not result in a significant increase in response amplitude. Length of prior habituation training had no signficant effect on test trial response amplitude in any of the response systems. The results concerning the effect of decreases in stimulus intensity on response amplitude are generally consistent with predictions derived from Sokolov's (1963) model of the orienting response.