Pigeons were trained on an observing-response procedure in which periods of VR 100 and EXT alternated unpredictably during a white light (mixed stimulus). During VR 100, responses on a food-producing key (the first key) were intermittently reinforced. Responses on the observing key (the second key) produced a green light (positive stimulus) when VR 100 was in effect, and a red light (negative stimulus) for EXT. The birds did not respond on either key during the negative stimulus, but they responded on the food-producing key when the positive stimulus appeared. When observing responses produced the positive or negative stimulus on FR, observing responses were maintained until the FR reached a maximum; beyond this, only food-producing responses occurred. When observing responses did not produce either stimulus, the observing-response rates feil to zero. With prolonged exposure to an FR 20 schedule of observing, observing-response rates during EXT were higher than during VR 100. Chlorpromazine hydrochloride decreased,the total response output but markedly increased observing-response rates except when it was administered before sessions of observing response extinction.In visual-discrimination experiments, different exteroceptive stimuli are correlated with different conditions of reinforcement. For example, pressing a lever (response A) will be reinforced in the presence of a green light (positive stimulus) but not in the presence of a red light (negative stimulus). We will refer to response A as the food-producing response. When the organism develops a visual discrimination, food-producing responses occur in the presence of the positive stimulus but not in the presence of the negative stimulus. However, the development of a visual discrimination implies the concurrent development of observing responses which enable the organism to perceive the positive and negative stimuli. For example, the organism may have to move its eyes or its head to see the stimulus. For the experimental analysis of observing responses, Wyckoff (1952) and Kelleher (1958) required subjects to make a clearly specified response, such as pressing a second lever (response B), in order to produce the appearance of the positive and negative stimuli. We will refer to response B as the observing response. The experiments of Wyckoff (1952) and Kelleher (1958) demonstrated that observing responses ceased when they did not produce the positive and negative stimuli or when "Now at Harvard Medical School.3 the stimuli were not correlated with reinforcement conditions. These results indicate that the appearance of the positive and negative stimuli reinforced observing responses.The present experiments investigated observing-response rates and observing-response patterns as a function of: 1) varying the number of observing responses required to produce the positive and negative stimuli; 2) giving prolonged exposure to a given observing-response requirement; and 3) administering chlorpromazine.

Squirrel monkeys were trained on a multiple schedule in which 10-min periods on a continuous shock avoidance schedule, indicated by a yellow light, alternated with 10-min periods on a 1.5-min variable interval schedule of food reinforcement (VI 1.5). A white light indicated that VI 1.5 was in effect, except for the middle 2 min of the period on VI 1.5, in which a blue light appeared and terminated with the delivery of a 0.5-sec unavoidable shock. Stable response rates developed in the avoidance and VI 1.5 components. However, the highest response rates occurred in the blue, preshock stimulus. A series of experiments showed that responding in the blue stimulus persisted even when responding had been extinguished on both the VI schedule of food reinforcement and the shock avoidance schedule. Responding in the blue stimulus ceased when the blue stimulus terminated without shock or when it terminated with a response-contingent shock. Each time responding ceased, it was restored by terminating the blue stimulus with an unavoidable shock. When the blue stimulus was on throughout each session and unavoidable shocks were delivered at regular 10-min intervals, responding was well maintained. These results show that in monkeys that have been trained on a continuous avoidance schedule, unavoidable shocks can maintain responding even under conditions where responses have no programmed consequences. Estes and Skinner (1941) demonstrated that a stimulus (pre-aversive stimulus) that repeatedly preceded an unavoidable shock suppressed the responding of rats on a fixed-interval schedule of food reinforcement. Many subsequent studies have extended this finding by showing that a pre-aversive stimulus suppresses the response rates of several other species on various schedules of positive reinforcement (e.g., Brady, 1955;Brady and Hunt, 1955;Azrin, 1956;Sidman, 1956;and Valenstein, 1959 the relative durations of the presence and absence of the pre-aversive stimulus; the degree of suppression was inversely related to the percentage of time that the pre-aversive stimulus was present.Sidman, Herrnstein, and Conrad (1957) first demonstrated that a pre-aversive stimulus could increase responding when a continuous shock avoidance schedule (Sidman, 1953) was used to maintain behavior; with further exposure to this procedure, however, the response rate during the pre-aversive stimulus gradually decreased toward the response rate that prevailed between presentations of the pre-aversive stimulus. When the conditioned avoidance response was extinguished, response rates decreased more slowly in the presence of the pre-aversive stimulus than in its absence.Herrnstein and Sidman (1958) found that -if monkeys had been previously conditioned on a shock avoidance schedule, the EstesSkinner procedure produced increased response rates in the pre-aversive stimulus even when a VI schedule of food reinforcement was used to maintain behavior. If the conditioned avoidance response was extinguished before the Estes-Skinner procedure -was instituted, respon...

We have found the squirrel monkey to be a useful experimental subject for behavioral and pharmacological experiments. This note presents techniques used for housing, feeding, handling, and administering drugs to these small primates.

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