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The purpose of this study was to compare gradients of skin resistance (SR) and skin potential (SP) responses generated by differing degrees of psychologically disturbing stimuli, and to determine the significance of the different wave forms of skin potential. SR and SP were simultaneously recorded during a word‐association test that included three levels of psychologically disturbing verbal stimuli. In addition to the a and b waves of the SP response, a second negative wave form, a2, was recorded. SR and all SP wave forms yielded positive gradients as a function of increasing stimulus intensity. Gradients based upon SR and total SP were close to identical. Magnitude measures, which include zero responses, of the SP wave forms yielded steeper gradients than measures of amplitude or frequency. The relative contribution of different SP wave forms to total SP varied with stimulus level.

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A previous study showed that a distinctive conditioned stimulus (CS) presented on the first trial of acquisition generated more responses after extinction than another CS presented regularly during acquisition. In this study all subjects were presented with a different distinctive CS on each first trial of 5 acquisition sessions. Subjects were then broken down into 7 groups which were tested, following extinction, for residual response strength of ( a) Day 1 novel CS; (b) Day 2 novel CS; (c) Day 3 novel CS; (d) Day 4 novel CS; (e) Day 5 novel CS; (/) the regular CS; and (g) a novel CS never presented before. Contrary to the previous study where a novel CS inhibited responding, Group 7 exhibited the most responding in this study. The results support a concept formation interpretation of the previous study and are difficult to explain from a "stimulus trace" or "identical elements" position.In a recent study (Burstein & Moeser, 1971), it was found that a distinctive stimulus regularly associated with the first trial of a series of acquisition trials generated more response strength when presented on a test trial following extinction than did another stimulus presented more frequently during the acquisition phase of the experiment. Specifically, for each of 5 daily acquisition sessions of 30 trials, different groups of pigeons were presented with a novel stimulus (a red conditioned stimulus, CS) on either Training Trial 1 or 20 or not at all. For all other acquisition trials, the CS was green. All responses on all trials were reinforced with 3-sec. access to a tray of Purina pigeon pellets. On Day 6, all subjects were extinguished on the "regular" green CS. Subjects were then placed in their home cages for 20 min. after which they were returned to the operant chamber and tested for residual response strength to either the distinctive red CS or the regular green CS.No significant differences were obtained in total test-trial responses of groups tested