The incremental stimulus intensity effect and habituation of evoked electrodermal responses

Abstract

The present paper reports two experiments which were designed to investigate the effectiveness of a gradually increasing series of stimulus intensities for producing response habituation to a higher intensity stimulus. Experiment 1 (N=45) employed 3 sec 1,000 Hz tones of moderate intensity, while Experiment 2 (N=36) employed 1 sec tones of relatively high intensity. In both experiments, skin conductance was measured while subjects received a series of constant intensity stimuli (Group C), an incremental series (Group I), or a random series (Group R). Eight trials were presented in Experiment 1, while in Experiment 2, 25 trials (5 blocks of 5 trials) were employed. The range of intensities employed for Groups I and R was 42-70 dB in Experiment 1, and 80-100 dB in Experiment 2. On the basis of previous work (O'Gorman & Jamieson, 1975), it was predicted that Group I would display smaller and fewer responses on the final trial in Experiment 1 and during the final trial block in Experiment 2 than would Groups C and R. However, neither experiment provided evidence for the 'incremental stimulus intensity effect'. In Experiment 1, there were no habituation differences between the groups, while in Experiment 2, the constant series resulted in significantly greater habituation than did the incremental series for both response frequency and response amplitude.