Classical Conditioning of Heart Rate and Electrodermal Activity

The research reported here was designed to explore the relationship between aversive visual stimuli and human physiological activity in a clssical conditioning situation. Specifically, the questions asked were (1) whether homicide pictures were effective stimuli in the classical conditioning of heart rate and electrodermal activity and (2) if conditioning occurred, what would be the form of the conditioned cardiac response. Thirty-six male undergraduate subjects were randomly assigned to one of three groups; (1) continuous reinforcement, (2) partial reinforcement i and (3) random reinforcement. A differential, delayed, classical conditioning paradigm was utilized with coloured slides of homicide victims and coloured slides of people in ordinary, everyday situations used as the two classes of unconditioned stimuli. A yellow light and a green light were used as the conditioned stimuli. Heart rate, electrodermal activity and respiration were recorded throughout a 10 minute adaptation period, 40 conditioning trials and 20 extinction trials. The results of the experiment clearly indicated that conditioning had occurred with both heart rate and electrodermal activity. Moreover, the use of a differential conditioning procedure demonstrated that conditioning had occurred with the homicide pictures but not with the non-homicide pictures. The form of the conditioned cardiac response to the homicide pictures was heart rate acceleration for the continuous reinforcement group and heart rate acceleration followed by deceleration for the partial reinforcement group. The unconditioned cardiac response was heart rate deceleration. The findings of this experiment were discussed within the framework of the theories of Lacey (1967), Obrist et al (1970a) and Elliott (1969).