Investigated the effects of an auditory judgment task on physiological responding in 2 experiments with 10 male undergraduates each. Ss were instructed to discriminate pure tones varying along a particular stimulus dimension. The stimulus set in Exp. I consisted of 5 tone intensities. In Exp. II, 5 tones differing in frequency were presented. In both studies, the difference between the initial acceleratory peak and the subsequent deceleration of the cardiac wave form reliably differentiated between stimuli on the basis of judgmental accuracy. Cortical slow-wave activity recorded in Exp. II covaried with accuracy of discrimination. (PsycINFO Database Record (c) 2006 APA, all rights reserved)