To What Does the Terminal Orienting Response Respond?

Previous authors suggested that the electrodermal orienting response to stimulus onset (OR) reflects cognitive processes related to the content of a stimulus while responses to stimulus offset (TOR) reflect processes related to stimulus duration. Experiment 1 tested the hypothesis that the OR and TOR are special cases of Ss responding to whatever part of the stimulus contains information necessary to make the requested judgment. The results clearly supported this alternative hypothesis. The Ss responded to stimulus onset when asked to judge the pitch (content) of a constant tone and to stimulus offset when asked to judge the terminal pitch of a varying tone. They responded to both the onset and offset of a stimulus when asked to compare the onset and offset pitch and when asked to judge stimulus duration. Experiment 2 partially replicated Experiment 1 in an attempt to assess the OR-TOR phenomenon in a second sensory modality (vision) and with a second dependent measure. The patterns of both electrodermal and heart rate responses were similar to those of Experiment 1 and to those observed by other authors.