Methods and mechanisms in electrodermal omission responding: a commentary on stimulus omission and the orienting response by Barry and O'Gorman.

Barry and O'Gorman (1987) have employed a response-averaging technique to demonstrate that electrodermal orienting responses (ORs) to omitted stimuli have unusually long latencies. They suggest that this latency delay provides evidence that omission ORs are "voluntary" responses initiated after a process of significance evaluation. The present commentary is addressed to both the methodological and theoretical aspects of their work. Firstly, some of the disadvantages of response averaging with electrodermal measures are reviewed, particularly as applied to omission ORs. Secondly, the use of OR latency as a dependent measure is discussed within an information-processing context. It is concluded that the assessment of stimulus significance does not systematically influence the latency of the OR. Hence, delayed latencies for omission responses probably reflect inaccuracies in the estimation of long inter-stimulus intervals, rather than a process of significance evaluation unique to the omission OR.