Effects of auditory frequency-shifts on zero and below-zero SCR habituation.

The purpose of the present experiment was to test a procedure for the measurement of effects of zero- and below-zero habituation (BZH) on responding to frequency shifts in auditory stimuli. The present procedure avoided some of the drawbacks of other procedures, that is, long duration, ambiguity in the definition of BZH, and inadequate control procedures. Two groups received 18 stimulus presentations each; group 1 received first a tone of 1000 Hz 12 times, then 1400 Hz (test stimulus 1) 3 times, and 1850 Hz (test stimulus 2) 3 times. Group 2 received the same stimuli, but 3, 12, and 3 times, respectively. The procedure had the advantages of short duration of the experiment, zero habituation and BZH were operationally defined (as 3 and 12 stimulus presentations, respectively), and there were adequate control conditions since a control group that did not receive stimulus change on the relevant trial was employed. The results showed no effects of stimulus shifts on responding to the test stimuli. Group 2 responded significantly less than group 1 across trials, though, and this may be explained by an inhibitory process elicited by changes in weak stimulation during the habituation process.