William F. Caul

Patterns of eating and drinking in socially-isolated rhesus monkeys☆

Abstract Three normally-reared and three animals which had been totally-isolated from social contact for the first year of life were tested in a series of experiments to determine the pattern and rate of eating and drinking. The monkeys were nine years old during these experiments and had been subjected to a variety of social and experimental conditions post-isolation. While the social isolates did not differ from the controls in the frequency and scheduling of eating and drinking during a day, they did consume more fluid and food during each meal. The isolates ate approximately 30 per cent more food per day over the course of a six month ad lib feeding period. Nevertheless, after an initial gain, they did not gain significantly more weight than did the controls. There was no evidence for increased motor activity among the isolates.

Effects of shock probability on heart rate of rats during classical conditioning

Abstract Heart rate of rats which received either 0%, 50%, or 100% shock reinforcement was obtained during a 10 day classical conditioning period. Pre-CS heart rate decreased over the ten-day conditioning period for the partially reinforced animals but remained at a constant level for the consistently reinforced groups, i.e., groups 0% and 100%. At the end of the initial 10 day conditioning phase the reinforcement conditions were changed. The 50% groups were tested for 5 days with extinction procedures, i.e., 0% shock, with no resulting change in pre-CS level. The group which had received 100% reinforcement during original training was also tested for 5 days on extinction and their pre-CS heart rates decreased significantly during this period. The 0% group was switched to 100% reinforcement for 5 days and their pre-CS rates also showed significant reduction as a result of the shift in reinforcement conditions. The cardiac rate data were not consistently related to activity levels during testing sessions. The data suggest that intertrial bradycardia is a function of the uncertainty or ambiguity of the situation with respect to the noxious consequences of conditioning stimuli.

Effects of Amobarbital on Discrimination Acquisition and Reversal

SummaryThirty-two rats injected with 20 mg/kg amobarbital and 32 given placebo were run 96 trials on a black-white discrimination followed by 160 trials of reversal training. Trials to the discriminanda were equated to provide speed data to the nonrewarded stimulus (S−) as well as to the rewarded stimulus (S+). Half the Ss were changed in drug state at the onset of reversal. The drug did not affect choice behavior or differential start speed to S+ and S− in acquisition although speeds closer to the goal were affected. In contrast, during reversal amobarbital Ss made fewer correct choice responses when compared to placebo Ss and displayed less pronounced differential start speed responding to S+ and S−. In addition to the main drug effect, a change of drug state facilitated reversal.

Effect of adrenocorticotropic hormone on appetitive discrimination learning in the rat

Abstract ACTH has been shown to have the effect of prolonging the extinction of avoidance behavior in animals. It has been established that this is an extraadrenal action of the hormone, most likely on central nervous system sites. One hypothesis suggested by these data gathered in aversive situations is that ACTH affects the storage and/or retrieval of learned responses. This experiment tested the generality of this view by administering ACTH to rats during acquisition and reversal of a black-white discrimination with food reward. ACTH had no effect of any kind on acquisition or reversal learning. Since these data do not support the memory hypothesis of the action of ACTH. some alternative explanation for the effects of the hormone on avoidance behavior must be sought.

Cardiac conditioned responses in avoidance and yoked-control rats

Rats in a yoked-control group were paired with partners which were given avoidance conditioning and extinction. Both animals received simultaneous and identical presentations of the CS and US throughout training. Heart rate data revealed that inter-trial rates declined over sessions for both groups. The cardiac responses to the CS increased in magnitude in the avoidance group over acquisition sessions as CARs increased in frequency. In the yoked-control group, however, the cardiac response diminished over sessions.

Influence of uncertainty on conditioned heart rates of monkeys

Abstract Two experiments were performed with rhesus monkeys on heart rate responses to classical aversive discrimination conditioning. The first investigated the effects of ratios of positive to negative trials and the effects of partial vs. continuous reinforcement. Discrimination learning was facilitated by reducing the number of positive (shocked) stimuli in comparison with the number of negative (unshocked) stimulus presentations. There was no difference between the heart rate accelerative responses elicited by partial as compared with continuous reinforcement but there was significant heart rate acceleration to the negative stimulus in the partially reinforced group while the two continuously reinforced groups did not respond to the negative stimulus. In the second experiment a warning signal preceded the presentation of the discriminative stimuli for one group of animals, but not for the second group. The inclusion of a warning signal changed the direction of the heart rate response from accelerative to decelerative. The results indicated that, within a single species, the conditioned heart rate response is very sensitive to experimental conditions.

Heart rate and skin conductance responding during three attention-direction tasks

Subjects were instructed to turn their attention toward: (1) feeling their internal bodily events (BODY task); (2) remembering events that happened to them on the preceding day (COGNITIVE task); and (3) looking at a series of slides (EXTERNAL task). They were assured that no verbal report would be required. Cardiac deceleration occurred during the BODY and EXTERNAL tasks. The BODY task was associated with a decrease on skin conductance measures.

Effects of delay conditioning and pseudoconditioning on heart rate and suppression of drinking

In each of two experiments, the tachycardic response to a CS was equivalent for classical delay conditioning and pseudoconditioning groups. Subsequent to conditioning sessions, the first experiment showed that the CS had effects on the initiation of drinking that were dependent on prior conditioning procedures, while the second experiment showed differential CS effects on the suppression of an already established drinking response.

Heart rate and skin conductance responding during three attention-direction tasks under distraction conditions

This study investigated the possibility that a failure to find cardiac acceleration to an environmental rejection task in a previous study was due to insufficient distraction in the experimental situation. The study was replicated, with distracting events added. An environmental intake task was associated with heart-rate deceleration during the first 60 sec. The rejection task and a third task involving attention to bodily events were not associated with significant heart-rate change. There were no differences in skin-conductance responding to the three tasks.

Effects of US intensity on heart rate in delay conditioning and pseudoconditioning

Heart rates of rats were obtained during seven aversive conditioning sessions and four extinction sessions. Two levels of shock intensity were used. The magnitude of the cardiac response to the CS was greater under high shock than under low shock. In the second experiment, the two shock levels were administered to two groups of rats in a pseudoconditioning procedure that specifically precluded CS-US pairing. The cardiac response to the CS in these two groups was indistinguishable from that of the comparable conditioning groups.