Physiological differentiation of sensory and cognitive tasks as a function of warning, processing demands, and reported unpleasantness.

Low and highly stressful sensory tasks (viewing slides of autopsy) were employed to assess the effects of stressful stimuli that required a minimal amount of cognitive elaboration. Cognitive (arithmetic, anagram, and digit-string memorization) tasks each at two levels of difficulty were matched for reported unpleasantness with autopsy slides to provide stimuli in which stress reactions were constant but cognitive processing requirements varied. Heart rate, skin potential level, and skin potential responses were monitored. Thirty-two subjects received two presentations of each type of task, one each of which was preceded by a warning signal. The results indicated that heart rate accelerated during cognitive tasks and decelerated during slide presentations of autopsy; the warning signal accentuated the heart-rate pattern associated with the task. Analyses of individual tasks revealed that heart rate was greater during the performance of difficult (more cognitively demanding) than easy cognitive tasks but that heart rate was not affected by the reported unpleasantness of the autopsy slides. Skin potential responses were more evident during the presentation of stressful (unpleasant) stimuli for both cognitive and sensory tasks; skin potential level, however, differentiated neither the tasks nor the stressfulness of stimuli within the tasks. These results are interpreted as being consistent with Lacey's hypothesis concerning cognitive elaboration, cardiac activity, and response patterning.