The Phasic Electrodermal Response As a Differentiated Complex Reflecting Stimulus Significance

ABSTRACT To examine the influence of stimulus significance on the shin conductance response (SCR) a 21 sec. 1000‐Hz tone was sounded variously In one car or the other. A click occurred during many tones, and a light signal always followed offset by 9 sec. Four groups were studied: one was told In press a pedal immediately on hearing any click; another only on hearing the click during a tone in a specified ear: a third was also to respond only to the specified ear, but was to withhold the press until the light following tone‐offset; a fourth group simply listened without and response. Each of a series of predictions regarding the incremental effect of stimulus significance on the SCR was confirmed, at each point at which information was delivered on any trial ‐ i.e., tone‐onset, click, tone‐offset, light‐onset. This was true for both independent as well us for within‐.S (between ear) comparisons. The presence of verbally‐induced “significance” as well as the complex nature of its influence indicated the presence of central mediation in the elicitation of “peripheral” SCRs. Was identified which correlated uniquel with motor reaction time, did not habituate, and did not correlate with SCRs elicited by other signals in this task. The execute SCRs did not simply reflect judgments of “significance” rather, it was qualitatively distinguished from other SCRs which, in general, were associated with stimulus “significance” There was some evidence of an alerting SCR too, hut this was less sharply defined.