Organismic, stimulus and task determinants of phasic and tonic heart rate and skin conductance changes

The effects of three variables (perceptual style 'leveling--sharpening', stimulus intensity and task) on tonic and phasic heart rate and skin conductance responses were studied. 24 levelers and 24 sharpeners received a series of 25 auditory stimuli under two instructions (task): in one task subject had to listen carefully to possible small differences between tones (intake task) and in the other task the subject had to count back silently and could neglect the tones (rejection task). One third of each group received tones of 50 dB, one third 75 dB and one third 100 dB. Results show that task has a strong effect on tonic responses in the direction predicted from Lacey's intake--rejection hypothesis. There is hardly any effect of task on phasic responses: only at the first trial heart rate tends to decelerate more in the intake than in the rejection task. Stimulus intensity does not influence tonic responses but very strongly affects phasic responses: deceleration to 50 and 75 dB, acceleration to 100 dB. GSR amplitude increases monotonically as a function of stimulus intensity. There is no difference between levelers and sharpeners with regard to tonic responses. Concerning phasic heart rate, sharpeners decelerate more than levelers and levelers have greater GSRs than sharpeners. It is suggested that tonic changes are relatively more under cognitive control, whereas phasic changes are more of a non-cognitive reflex-like nature. A relationship between the distinction arousal-activation as proposed by Pribram and McGuinness (1975) and the results of this experiment was suggested.