for many years, it has been well-accepted that the amplitude of the phasic orienting response is directly dependent on both stimulus intensity and novelty, at least within innocuous intensity ranges. Surprisingly, the joint contribution of these stimulus parameters has not been convincingly specified in the literature. A two-step analytical procedure, which is logically necessary to provide a valid solution to the problem, is outlined. Data are then presented which demonstrate that there is a multiplicative relationship between the two parameters in their joint determination of response amplitude. That is, stimulus intensity and novelty interact in the production of the phasic electrodermal orienting response to innocuous stimuli. © 1993.