Muscle tension in human operant heart rate conditioning

The physiological mechanism involved in human operant heart rate conditioning is not known. If skeletal muscle tension is a mediator, it should be possible to generate significant heart rate increases by inconspicuous voluntary muscle tension. Eleven subjects were instructed to generate inconspicuous muscle tension for 90-second periods. No gross muscle movements were observed, but average heart rate during the trials was over 13 beats-per-minute greater than pre-trial base lines. Respiratory pattern changes and surface electromyogram changes did not reliably correlate with heart rate increases. Inconspicuous muscle tension could be a mediator in human operant heart rate conditioning, and cannot be ruled out by absence of change in respiratory pattern or electromyogram.     

Bidirectional operant conditioning of heart rate in rats with sucrose reward

Sucrose was used to reinforce heart rate (HR) increases in one group of unrestrained rats and to reinforce decreases in another. A third group received noncontingent sucrose presentations, and a fourth was presented with an empty dipper. After 10 conditioning sessions HR, as measured by changes in tonic levels, was significantly greater in the Fast group than in the Noncontingent group, which in turn maintained significantly higher levels than the Slow group. There was no difference between the Noncontingent and No-sucrose groups. Behavioral observations indicated that the Fast animals increased the percentage of time spent in such high-HR categories as rearing and walking; however, there were no corresponding systematic decreases in the Slow animals. Moreover, the Fast and Slow groups differed significantly with regard to the HRs associated with five behavioral categories. The overall pattern of results suggests that some degree of cardiospecific effect may have been exerted by the operant contingencies.     

Social reinforcement of operant behavior in rats: a methodological note.

An apparatus was developed to study social reinforcement in the rat. Four Long-Evans female rats were trained to press a lever via shaping, with the reinforcer being access to a castrated male rat. Responding under a fixed-ratio schedule and in extinction was also observed. Social access was found to be an effective reinforcer. When social reinforcement was compared with food reinforcement under similar conditions of deprivation and reinforcer duration, no significant differences were observed.     

A cellular analogue of operant conditioning.

Using the hippocampal-slice preparation, we attempted to model operant conditioning in vitro by reinforcing pyramidal cell bursting responses with local micropressure applications of transmitters and drugs. The same injections were administered independently of bursting to provide a "noncontingent" control for direct pharmacological stimulation or facilitation of firing. The results suggested that the bursting responses of individual CA1 pyramidal neurons may be reinforced in a dose-related manner by response-contingent (but not noncontingent) injections of dopamine and the selective dopamine D2 agonist, N-0923. N-0924, a stereoisomer of N-0923 that is largely devoid of D2-agonist activity, failed to reinforce CA1 bursting. Burst-contingent injections of the excitatory neurotransmitter glutamate also failed to reinforce CA1 bursting; indeed, the glutamate applications (whether contingent or random) reduced the likelihood of bursts while increasing the frequency of solitary spikes. Reinforcement delays exceeding 200 ms largely eliminated the reinforcing efficacy of the D2 agonist N-0437 in CA1 operant conditioning. The results are consistent with the suggestion that the behaviorally reinforcing effects of dopaminergic agents can be modeled in vitro in the hippocampal-slice preparation.     

Controlling pain reports through operant conditioning: a laboratory demonstration

Operant conditioning of pain reports was studied in two laboratory experiments. In the first one 5 subjects were given the same pain stimulus on 15 trials and their recorded pain ratings gave no systemic trends across subjects. 8 other subjects received the same pain tests but on some of the trials increases or decreases in pain ratings were verbally reinforced while the noxious stimulus was held constant across trials. Clear and significant differences between reinforced increases and decreases in pain reports were observed. In Exp. 2, 5 subjects were given neutral feedback and systematically decreasing levels of noxious stimulation, resulting in a good correlation between pain ratings and stimulation level. 5 subjects were provided reinforcement for increasing pain reports while the pain stimulus was systematically reduced. Increases in pain reports were observed simultaneously with large decreases in the level of the noxious stimulus. Results of these experiments support the operant conception of pain.     

Instructional control of human operant responding during extinction following fixed-ratio conditioning

When given pre-conditioning instructions correctly indicating the maximum number of reinforcements obtainable, subjects made few responses during extinction following FR 10 conditioning. More extinction responses occurred when the maximum-reinforcement instructions suggested that reinforcements were obtainable during extinction. The highest rates of responding during extinction were produced by subjects who had no maximum-reinforcement instructions.     

Overshadowing in operant conditioning as a function of discriminability

Pigeons were trained in an operant, go/no-go, discrimination by successive presentations of discrete, positive and negative trials. In separate groups, the rate of discriminaion learning based on an auditory cue, on visual cues of different discriminability, and on combined auditory and visual cues was determined. The auditory cue was tone/no-tone, the visual cue was a difference in brightness level on the key. Following discrimination training, stimulus control was tested in extinction by presenting tone or notone at each of four key-brightness levels.Learning was more rapid with two cues than with either cue singly, demonstrating summation. The contribution made by the tone cue to the learning of the discrimination decreased with increasing discriminability of the light cue. The control exerted by the tone cue also decreased (i.e., the tone cue was overshadowed) with increasing discriminability of the light cue. In certain cases, the tone cue decreased control by brightness, showing that in two-cue discriminations each cue may reduce the control exerted by the other.     

Recent advances in operant conditioning technology: a versatile and affordable computerized touchscreen system.

We report the construction of a new operant chamber that incorporates modern computer, touchscreen, and display technologies. An LCD display was housed in the front wall of a lightweight Plexiglas chamber. An Apple eMac computer was used to present visual stimuli on the monitor and to control other chamber events. Responses to the stimuli were recorded using a transparent resistive-type touchscreen that overlaid the monitor. The resulting system is simple and inexpensive to construct but powerful and flexible enough to explore a broad range of issues in animal learning and behavior.     

Multiple memory stores and operant conditioning: a rationale for memory's complexity

Why does the brain contain more than one memory system? Genetic algorithms can play a role in elucidating this question. Here, model animals were constructed containing a dorsal striatal layer that controlled actions, and a ventral striatal layer that controlled a dopaminergic learning signal. Both layers could gain access to three modeled memory stores, but such access was penalized as energy expenditure. Model animals were then selected on their fitness in simulated operant conditioning tasks. Results suggest that having access to multiple memory stores and their representations is important in learning to regulate dopamine release, as well as in contextual discrimination. For simple operant conditioning, as well as stimulus discrimination, hippocampal compound representations turned out to suffice, a counterintuitive result given findings that hippocampal lesions tend not to affect performance in such tasks. We argue that there is in fact evidence to support a role for compound representations and the hippocampus in even the simplest conditioning tasks.     

The effects of distributed training on retention of operant conditioning in human infants

Long-term retention of operant footkicking acquired in the mobile conjugate reinforcement paradigm was assessed as a function of the distribution of training time. In the first study, 3-month-old infants were trained for either one 18-min session or for two 9-min or three 6-min sessions separated by 24-hr intervals. All infants exhibited retention during a test administered immediately after training, but only those trained in a single session continued to perform the conditioned response during cued-recall tests 7 or 14 days later. Infants trained in three sessions showed no evidence of remembering the contingency even after a week. A warm-up decrement, seen in the day-to-day performance of infants in the distributed conditions, was eliminated in the second study by the interpolation of a nonreinforcement period at the outset of daily sessions. This procedure also enhanced long-term retention such that infants trained in three 6-min session now remembered the contingency for 14 days and did not differ from infants who had received a single 18-min session. Whether distributed training facilitates or impairs long-term retention appears to depend on the opportunity for infants to acquire a sufficient number (or kind) of effective retrieval cues during original learning.     

Overshadowing of a context aversion by a novel incentive in operant conditioning

Two experiments examined the processes underlying the suppression of instrumental behaviours by lithium in rats, as reported by Meachum (1988 and this issue). Experiment 1 examined whether presenting a novel sucrose solution prior to lithium chloride administration would overshadow aversion learning to either the stimuli of the operant chamber or to familiar food pellets. After lever pressing had been established, and in the absence of responding, animals received free deliveries of a novel sucrose solution, familiar food pellets, or both, or they were exposed to only the cues of the operant chamber, prior to lithium injections. Lever pressing for food pellets was then assessed. It was found that the animals receiving the novel sucrose, either alone or with the familiar food pellets, pressed more for pellets than either the group receiving only food pellets or the group exposed to only the context. In addition, there was no appreciable difference in the response rates between the context-only group and the group that received the familiar food pellets. These outcomes were interpreted in terms of the novel sucrose overshadowing aversion learning to the context. Experiment 2 investigated whether in fact aversive contextual conditioning could be obtained using the present parameters. This was accomplished by directly manipulating the contexts. In this experiment animals were trained to lever press in two distinctive contexts. Subsequently, one context was paired with the novel sucrose, and the second was experienced in the absence of reinforcement prior to toxicosis. During a subsequent non-reinforced test it was found that responding in the context paired with the novel sucrose was considerably higher than responding in the context that was experienced alone. These findings stand in contrast to the taste-mediated contextual potentiation observed when a consumatory response is used to assess aversive contextual conditioning.     

The application of operant conditioning techniques in a secondary school classroom

The effects of teacher praise and disapproval on two target behaviors, inappropriate talking and turning around, were investigated in a high school English class of 25 students. The contingencies were applied to all students in the experimental class utilizing a multiple baseline experimental design in which the contingencies were aimed first at decreasing inappropriate talking behavior and then at decreasing inappropriate turning behavior. Observations were made of both student and teacher behavior. The results demonstrated that the combination of disapproval for the target behaviors and praise for appropriate, incompatible behaviors substantially reduced the incidence of the target behaviors in the experimental class. Observations of these behaviors in a control class of 26 students taught by the same teacher revealed no particular changes. The findings emphasize the importance of teacher-supplied social contingencies at the secondary school level.     

Varying temporal location of a conditioned stimulus in heart rate conditioning ofMacaca mulatta

The several functions that a stimulus can assume were investigated in a Pavlovian conditioning procedure. The subjects were six rhesus monkeys; the response under observation was heart rate. The conditioning began with a temporal separation of zero between a signal and a regularly repeating electric shock; the signal was then moved to a series of earlier locations in the inter-shock interval. After six sessions at each location, two sessions followed in which only the shock was delivered periodically. The findings included: (1) A two-phased conditioned cardiac rate response seen at the first location became more multiphasic and irregular during longer intervals between signal and shock; (2) the location where the conditioned response peaked became increasingly variable as the signal was moved back, but this variability maintained a constant proportion to the signal-shock interval; and, (3) heart rate during a presignal period, and during a comparable period in shock only sessions, was generally deceleratory early in training and acceleratory thereafter. Sessions with the signal showed heart rate in the presignal period to have become acceleratory earlier in training than sessions with shock only. The data pertain to stimulus control over heart rate as a function of: (A) the temporal proximity of a signal to an aversive stimulus; and, (B) the presence or absence of the signal. The use of appropriate response units in cardiac conditioning is also discussed.     

The sociological study of suicide: methodological issues

This paper is a critical review of selected methodological issues in the sociological study of suicide. It first distinguishes between two broad research orientations: the micro and macro approaches to the subject. The paper than focuses on a critical assessment of the dominant macro-level methodology. Three recurrent problems are identified: measurement issues on four key variables (suicide and parasuicide, economic conditions, religion, and political conditions such as war); problems in studying the effect of mass media stories on suicide; and reasons why we need to adopt a cross-national method in order to test sociological theories for contextual effects. Partial remedies to many of these problems are discussed.