Task demand as reflected in catecholamine excretion and heart rate.

Immediate effects and aftereffects of exposure to a color-word conflict task were studied in two groups of subjects, one of which performed the task without auditory interference ("single conflict"), the other with auditory interference ("double conflict"). Physiological arousal indices were more susceptible than performance measures to the level of task demand. Thus, the higher demand imposed by the double-conflict task was reflected in relatively larger increases of adrenaline excretion and heart rate, both during the conflict task and during the subsequent arithmetic task, whereas the performance measures remained unaffected.