Vigilance and the reinforcing properties of shock

There have been some observations to indicate that waiting for a shock is stressful, that the coining of an anticipated shock can serve as a tension reliever, and that failure to obtain an anticipated shock is more stressful than being shocked. Based on these observations, the following hypotheses were tested. If it is true that failure to receive shock is more stressful than the shock itself, it should be possible to train an animal to bring on a shock that had failed to come when anticipated. If a period of anticipating shock is stressful, and shock serves as a reliever of the stress, it should be possible to train an animal to perform a response instrumental to bringing on the shock sooner. Results indicated that shock does seem to serve as a reliever, that waiting for shock is stressful, but that failure to receive an anticipated shock under these circumstances is not more stressful than the shock itself. In addition, it was found that subjects learned to produce shock instrumentally if the shock was inevitable and could thus be brought about sooner. Results were inconclusive, though generally negative, on the issue of whether S’s would produce an avoidable shock that had failed to come when anticipated.     

Hippocampal injections of amyloid beta-peptide 1-40 impair subsequent one-trial/day reward learning

The injection of amyloid beta-peptide (Abeta) into rat CNS has been reported to induce cellular neuropathology. The present study investigated whether multiple intrahippocampal injections of Abeta 1-40 would impair one-trial/day reward learning 14 days later. Twenty-four male Sprague-Dawley rats, 3-4 months old, were injected with either Abeta 1-40 or distilled water into seven hippocampal sites bilaterally. Ten rats received 3 nmol Abeta 1-40 in 2 microl of distilled water per injection site, while 14 rats received distilled water alone. Following a 9-day recovery period, rats were gradually food deprived to 82% of their initial body weight. Fourteen days after the intrahippocampal injection, all rats received an initial training trial and three subsequent daily retention trials. Rats receiving Abeta 1-40 were significantly impaired on the second retention trial in terms of accuracy (number of unbaited alleys entered) and on the second and third retention trials in terms of speed (reciprocal of latency to reward). Histological analysis showed that Abeta 1-40 injections produced significant neuronal loss and gliosis. Abeta 1-40 immunoreactivity persisted locally at the injection site and in macrophages 2 weeks following the hippocampal injections. These effects appear to be sequence-specific; rats receiving Abeta 1-42 with a scrambled peptide sequence did not differ significantly from rats receiving distilled water alone in retention of the learning task or degree of histological damage.     

Preconditioning of reinforcing properties to an exteroceptive feedback stimulus

Three groups of rats were given Pavlovian preconditioning by means of a yoking procedure and subsequently trained to avoid. One group received a light stimulus during preconditioning at the same times as the master avoiding animals received an exteroceptive feedback stimulus. During the subsequent avoidance training, this group was then given the same light stimulus as a feedback stimulus on successful avoidance trials. The group learned two-way avoidance in about the same number of trials as one-way avoidance is typically learned and substantially faster than two other control groups. These data indicate that feedback stimuli develop reinforcing properties by a Pavlovian mechanism. The data of the control groups indicate that feedback stimuli do not provide “information” about responding in the present situation.     

A note on some reinforcing properties of university lectures

Contingency management systems in university courses have sometimes assigned the role of reinforcing stimulus to lectures and demonstrations. Attending a lecture was made contingent upon having previously finished certain course assignments. The present paper investigated some variables that control student attendance at lectures. Attendance remained high throughout each course at those class meetings where quizzes contributing to course grades were given or where impending quizzes were discussed. Attendance at lectures over the reading assignments or over material unrelated to course quizzes rapidly declined. When students were given course credit for attending these lectures, or when the lectures included information for future quizzes, attendance increased. When attending these lectures was made contingent upon having completed certain assignments the prior week, no increase in assignment completion was noted and the attendance at the lectures decreased even further. All lectures were given during one class meeting each week. Attendance at the other class meetings during the week remained stable.     

Discriminative and reinforcing properties of two types of food pellets

In Experiment I some discriminative functions of food pellets were studied by developing a multiple schedule of reinforcement (mult FR 30 FI 3) in which the delivery of a standard laboratory food pellet as a reinforcer set the occasion for reinforcement on every 30th response (FR 30), and the delivery of a sucrose food pellet as a reinforcer set the occasion for reinforcement after a 3-min interval (FI 3). Discriminative stimulus control by the type of pellet was also demonstrated by reversing the operant discrimination and having the standard pellet control the FI 3 and the sucrose pellet control the FR 30. In Experiment II a mult FR 30 FR 30 with two bars was developed; a standard food pellet was followed by an FR 30 on Bar 1 and extinction (ext) on Bar 2, while a sucrose pellet was followed by an FR 30 on Bar 2 and ext on Bar 1. A control rat was placed, for comparison, on a mixed (mix) FR 30 FR 30 schedule with two bars, but neither bar correlated with the type of food pellet. In Experiments I and II the similarity between pellet controlled multiple schedules and multiple primed schedules was discussed, as was the comparability of transitions and effectiveness of control between pellet controlled multiple schedules and multiple schedules providing continuous exteroceptive stimuli.     

The rapid-smoking technique: Some physiological effects

The effects of rapid smoking on the blood pressure, pulse rate and cardiac functioning of 58 smokers (30 women and 28 men) are reported. All subjects were healthy volunteers, 45 were under 40 yr of age, the remaining 13 between 40 and 50 yr. They received between 6 and 12 rapid smoking sessions. It was found that, in both the under and over 40 age groups, blood pressure levels and pulse rates increased significantly following rapid smoking sessions. There were, however, significant decreases between sessions and no evidence of a cumulative effect of successive rapid smoking sessions. Some qualitative changes in cardiac functioning were observed, namely the appearance of T wave flattening and S-T depression. None of the changes were considered to be of sufficient magnitude to necessitate exclusion from the programme, but confirm the need to monitor closely the physiological functioning of persons undergoing rapid smoking.     

A test of the reinforcing properties of stimuli correlated with nonreinforcement

The information hypothesis of conditioned reinforcement predicts that a stimulus that “reduces uncertainty” about the outcome of a trial will acquire reinforcing properties, even when the stimulus reliably predicts nonreinforcement. Four pigeons' key pecks produced one of two 5-sec stimuli with 0.50 probability according to a discriminated variable-interval schedule. One stimulus was followed by reinforcement; a second stimulus was followed by blackout. To the same extent, therefore, both stimuli reduced uncertainty about the possibility that food would arrive at the termination of the schedule interval. When a second key in the chamber was lighted, each peck on it could produce the stimulus preceding reinforcement, the stimulus preceding nonreinforcement, a novel stimulus, or no stimulus, across separate conditions. The stimulus preceding food maintained responding at substantial levels on the second, stimulus-producing, key. Such responding was not maintained by other stimuli. These data, replicated when the stimuli were reversed on the variable-interval schedule, do not support the prediction that uncertainty-reducing stimuli are necessarily conditioned reinforcers.     

Some properties of binormamin

Three properties of the binormamin criterion for analytic transformation in factor analysis are discussed. Particular reference is made to Carroll's oblimin class of criteria.The research reported in this note was supported in part by the Program in Applied Mathematics and Statistics. National Science Foundation, and by the National Institute of Education, Department of Health, Education, and Welfare.     

Testing the reinforcing properties of S-: a replication of Lieberman''s procedure

A critical issue in testing theories of observing is whether the stimulus associated with extinction (the S-) reinforces observing responses. In previous experiments, subjects have been trained to make observing responses that produce both the S- and the stimulus correlated with reinforcement (the S+). Then, either the S+ or the S- has been withheld. Conflicting results have been attributed to differences among species. In the present experiments, pecking one key by master pigeons was reinforced with grain on a variable-ratio extinction schedule. Yoked pigeons received the grain on a variable-interval, extinction schedule controlled by the variable-ratio performances of the master birds. For both groups, concurrent pecking on a second key was reinforced on a variable-interval schedule with displays of discriminative stimuli. Subsequently, either the S+ or the S- was eliminated from the procedure. Omission of S+ produced a large decrease, as predicted by traditional conditioned reinforcement accounts of observing. By itself, S- did not maintain observing. A smaller and less reliable decrease, comparable to that obtained by Lieberman (1972) with rhesus monkeys, occurred when S- was eliminated. This replication with pigeons of Lieberman's results indicates that they are not species-specific, and the fact that observing was not maintained by S- alone suggests that the decrease obtained when S- was omitted is not attributable to the reinforcing power of S-.