Stimulus Repetition, Change, and Assessments of Sensitivities of and Relationships Among an Electrodermal and Two Plethysmographic Components of the Orienting Reaction

Abstract

ABSTRACT Twenty S s were presented with 15 300‐msec tones (for half the S s) or lights (for the remaining S s) followed by a change trial to the other modality. There was highly reliable habituation in the electrodermal skin resistance response (SRR) and the plethysmographic pulse volume (PV), but no clear habituation in the plethysmographic blood volume (BV). Change produced reliable increases in all three orienting‐reaction (OR) components. Application of signal‐detection methods showed SRR to be a more sensitive index of both initial OR and OR to change than either PV or BV, which were not different. Neither PV nor BV were correlated with SRR, but the BV‐PV correlations were significant, and, when corrected for attenuation, approximated +.75. The problem of why the plethysmographic OR components sometimes habituate to stimulus repetition, and sometimes do not, was discussed, but it was concluded that while some possible explanations have been eliminated by the present results, the problem itself still awaits solution and poses a challenge to psychophysiologists.