Appetitive Responding Research Articles

REMOTE EFFECTS OF AVERSIVE CONTINGENCIES: DISRUPTION OF APPETITIVE BEHAVIOR BY ADJACENT AVOIDANCE SESSIONS

Disruption of ongoing appetitive behavior before and after daily avoidance sessions was examined. After baselines of appetitive responding were established under a fixed-interval 180-s schedule of food presentation, 4 rats were exposed to 40-min sessions of the appetitive schedule just prior to 100-min sessions of electric shock postponement, while another 4 rats received the 40-min appetitive sessions just following daily sessions of shock postponement. In all 8 subjects, fixed-interval response rates decreased relative to baseline levels, the effect being somewhat more pronounced when the avoidance sessions immediately followed. The disruption of fixed-interval responding was only partially reversed when avoidance sessions were discontinued. During the initial exposure to the avoidance sessions, patterns of responding under the fixed-interval schedule were differentially sensitive to disruption, with high baseline response rates generally more disturbed than low rates. These disruptions were not systematically related to changes in reinforcement frequency, which remained fairly high and invariant across all conditions of the experiment; they were also not systematically related to the response rates or to the shock rates of the adjacent avoidance sessions. The results, while qualitatively resembling patterns of conditioned suppression as typically studied, occurred on a greatly expanded time scale. As disruption of behavior extending over time, the present data suggest that some forms of conditioned suppression are perhaps best viewed within a larger temporal context.

Asymmetrical effects of Pavlovian excitatory and inhibitory aversive transfer on Pavlovian appetitive responding and acquisition

Predictions of a theory of Pavlovian motivational transfer, which incorporates principles of both the theory of reciprocal inhibition and the Rescorla-Wagner model, were tested in several Pavlovian aversive to Pavlovian appetitive transfer tasks. As predicted, the presence of a signal for an aversive event, conditioned stimulus (AV CS+), reliably suppressed performance of appetitive conditioned responses (CRs) whether imposed during acquisition or on independently established responding. Acquisition of appetitive responding to a novel CS reinforced in compound with an AV CS+, however, was enhanced (“superconditioning”). This observation suggests that the effects of a discrepancy between expectation and actual outcome on a conditioning trial are influenced by the affective value of both the expectation and the reinforcer. These transfer effects were not symmetrical for an inhibitory aversive stimulus (AV CS−). An AV CS− did not enhance appetitive responding compared to a random control condition, nor did the AV CS− reduce (i.e., block) appetitive conditioning to a novel CS when appetitive reinforcement occurred in the presence of the AV CS−. Comparison of the two shock-exposed conditions with a naive control condition suggests that previous results that were apparently consistent with inhibitory aversive enhancement and blocking of appetitive conditioning may have been due to aversive context conditioning.

Learned helplessness and immunization: Sensitivity to response-reinforcer independence in immunized rats.

In experiments 1 and 2, we examined the learned helplessness and immunization effects using a test in which appetitive responding was extinguished by delivering noncontingent reinforcers. Contrary to learned helplessness theory, "immunized" animals showed performance virtually identical to that of animals exposed only to inescapable shock, and different from nonshocked controls. Experiment 2 suggests that the helplessness effect and the lack of immunization are not due to direct response suppression resulting from shock. In Experiment 3, where the immunization effect was assessed by measuring the acquisition of a response to obtain food when there was a positive response-reinforcer contingency, immunization was observed. These results cannot be explained on the basis of proactive interference, but suggest that animals exposed to the immunization procedure acquire an expectancy of response-reinforcer independence during inescapable shock. Thus, immunization effects may reflect the differential expression of expectancies, rather than their differential acquisition as learned helplessness theory postulates.

Learned helplessness and immunization: Sensitivity to response–reinforcer independence in immunized rats.

In experiments 1 and 2, we examined the learned helplessness and immunization effects using a test in which appetitive responding was extinguished by delivering noncontingent reinforcers. Contrary to learned helplessness theory, "immunized" animals showed performance virtually identical to that of animals exposed only to inescapable shock, and different from nonshocked controls. Experiment 2 suggests that the helplessness effect and the lack of immunization are not due to direct response suppression resulting from shock. In Experiment 3, where the immunization effect was assessed by measuring the acquisition of a response to obtain food when there was a positive response-reinforcer contingency, immunization was observed. These results cannot be explained on the basis of proactive interference, but suggest that animals exposed to the immunization procedure acquire an expectancy of response-reinforcer independence during inescapable shock. Thus, immunization effects may reflect the differential expression of expectancies, rather than their differential acquisition as learned helplessness theory postulates.

Influence of naloxone on the effects of lsd in monkeys

Three stump-tailed monkeys were trained in an appetitive behavioral task. Administration of 0.1 mg/kg of lysergic acid diethylamide (LSD) moderately disrupted performance acutely, and produced abnormal motor activity. With repeated administration of LSD, motor activity and task responding returned to normal. When 1.0 mg/kg of naloxone was administered prior to administration of LSD in a crossover design, appetitive responding was abolished acutely in all animals and behavior was substantially more disrupted than with LSD alone. Tolerance did not occur with repeated administration of this combination of drugs. Endorphins and/or opiate receptors may act to attenuate the effects of hallucinogenic agents, and may subserve the development of tolerance to these effects.

Influence of visual conditioned stimulus characteristics on the form of Pavlovian appetitive conditioned responding in rats.

Influence of visual conditioned stimulus characteristics on the form of Pavlovian appetitive conditioned responding in rats.

Differential effects of omission contingencies on various components of Pavlovian appetitive conditioned responding in rats.

Five experiments with rat subjects investigated the effects of omission and partial reinforcement contingencies on five individual behaviors evoked by visual and auditory conditioned stimuli paired with a food unconditioned stimulus. The effects of omission depended on the behavior on which that contingency was placed: One behavior was eliminated, one was unaffected, and three were reduced relative to the performance of yoked controls. Partial reinforcement resulted in lower frequencies of three behaviors and higher frequencies of two behaviors, compared with performance under consistent reinforcement. A partial reinforcement extinction effect was noted with one behavior but not with the others. These results are related to the possible role of instrumental conditioning contingencies in generating conditioned behavior in this appetitive conditioning preparation and to the independence of individual components of a complex conditioned response.

WARMUP IN AVOIDANCE AS A FUNCTION OF TIME SINCE PRIOR TRAINING1

On avoidance procedures, rats and pigeons typically show warmup effects, characterized by improving performance within sessions and loss of the improvement ("warmup decrement") between sessions. Between-session losses were examined by varying the time between periods of avoidance training. In one experiment, rats lived fulltime in conditioning chambers while intermission intervals were varied. In a second experiment, the animals lived in home cages between sessions; timeout intervals were introduced at midession, producing recurrence of warmup in the second half-session. In both experiments, the warmup decrements increased substantially as the timeout or intersession intervals were increased from zero to 30 minutes. With intervals of 60 or 120 minutes, the decrements approached or exceeded those obtained with intervals of a day or more. When avoidance was interposed between appetitive sessions, the appetitive responding was disrupted, but this seemed unrelated to the warmup or to the proficiency of avoidance. The warmup in avoidance shares characteristics with transient punishment effects, with the Kamin effect, and with habituation phenomena, but it is premature to assume that they reflect common processes.

An opponent-process interpretation of postshock bursts in appetitive responding

While eight food-deprived rats pressed a lever for food during daily 1-h sessions, four CS-Shock2 trials were presented. Trials were preceded by either a Shock1 of .25, .50, .75 mA or no Shock1. It was found that the rate of appetitive responding during the CS was greater on Shock1-CS-Shock2 trials relative to CS-Shock2 trials. The data indicate that the phenomenon of postshock bursts in responding can occur in the absence of a signal for safety after shock. The results conform to the predictions of the opponent-process theory of motivation.

The effects of chronic mescaline administration on operant behavior in the pigeon

A dose of 6.5 mg/kg mescaline which acutely abolishes fixed-ratio appetitive responding in pigeons becomes progressively less disruptive with repeated administration. When responding reaches about 60% of baseline (in about 3 weeks) no further tolerance occurs. A dose of 3.5 mg/kg mescaline acutely lowers responding to about 60% of baseline and repeated administration of this dose continues to produce approximately the same response deficit. Discontinuation of both doses results in an immediate return to baseline levels of responding. Two possible mechanisms underlying this two-stage action of mescaline seen in this and other studies are discussed. The endogenous hallucinogen hypothesis of schizophrenia is considered in light of the existence of tolerance-resistant hallucinogenic drug effects.

Ontogeny of thirst in the infant rat.

The development of water drinking in response to thirst stimuli was found to be precocious and sequential in the neonatal rat. It was studied in suckling rats with a technique that took advantage of their vigorous consummatory reflexes and minimized appetitive responding. Responsiveness to the following thirst challenges appeared in the suckling rat with a clear timetable: cellular dehydration at 2 days of age, hypovolemia induced by colloid dialysis at 4 days, and beta-adrenergic activation at 6 days. Responsiveness to deprivation from mother's milk was vigorous at the earliest day tested (2 days) but could not be distinguished from hunger. Rats weaned, isolated, and tested as miniadults responded appetitively to thirst challenges as early as 16 days of age. But they required a warm environment, optimum access to the water source, and sufficient time to respond. As revealed by consummatory responding, the controls of water drinking mature weeks before they are required. They precede the maturation of capacities for sustained appetitive responding. These appear in the last week of the suckling period, yielding animals that are prepared for adult, thirst-motivated behavior at the onset of weaning.

Effects of reinstatement procedures on retention of differential appetitive responding

Forty male hooded rats received single alternation runway training followed by a 24-day retention interval. On the 25th retention day, reinstatement procedures (re-exposure to the stimuli from original training) were administered: Groups IRA and ORA (N = 10 each) received 10 alternating reward and nonreward placements into a goalbox similar to that of the runway; controls, IRC and ORC (N = 10 each) received 10 placements into an empty neutral box. For half of each group, placements occurred either inside or outside of the experimental room (IR or OR). All rats then received single alternation retraining. Results showed that the alternation-reinstatement procedure reliably facilitated recall and re learning of alternation responding. Retention was minimally affected by the experimental room stimuli alone. However, retention was greatest when the alternation-reinstatement procedure occurred inside the experimental room (Group IRA).

Motivating prairie dogs

Appetitive responding (double alternation and DRL) in tamed prairie dogs (Cynomys ludovicianus) was effected with food and water reinforcement. The result was generally inconsistent performance and/or death by starvation or dehydration. While wild prairie dogs did not need drinking water, tamed captives became vitally dependent. This need was met by operant responding only when terms of work were easy; when the terms of work were moderately difficult, some prairie dogs stopped responding and then died of dehydration.

Cortical spreading depression and thirst☆

Abstract Bilateral, but not unilateral, cortical spreading depression inhibited drinking of water, whether motivated by water deprivation or cholinergic brain stimulation. This inhibition of behavior does not appear to be specific to cholinergic mechanisms, thirst, or appetitive responding. Rather, a more general blocking of neurobehavioral systems due to cortical deactivation seems likely.

Discriminated punishment: avoidable and unavoidable shock.

Warning stimuli for two punishment conditions were alternated with periods of appetitive responding by rats. In either warning stimulus, the first response produced a brief shock, terminated the stimulus, and started an interval during which the baseline appetitive schedule was in effect. Not responding resulted in stimuli of random duration, which terminated with a shock under one condition and without a shock under the other. Each subject was exposed to several shock intensities, with trials for the two conditions programmed during alternate portions of the session. In general, response frequency in the warning signal for either condition decreased with increasing intensity; however, at a given intensity, responding was more frequent in the stimulus invariably terminating with shock than in the stimulus terminating without shock when no response was made. The frequency difference was greatest at intensities intermediate between those producing minimal and maximal suppression.

Chlorpromazine-induced suppression in appetitive and avoidance responding as a function of shock intensity.

This experiment investigated the role of shock intensity in determining the effects of chlorpromazine on appetitive and avoidance responses maintained concurrently in individual rats. Ss were trained and tested in a two-lever cage. Pressing one lever produced food according to a variable interval schedule of reinforcement; pressing the second lever at the onset of a warning signal avoided shock. After performance on this concurrent schedule had become stable, the effects of chlorpromazine in doses of 1.0, 2.0, and 4.0 mg/kg of body weight were observed at three intensities of shock: 0.5, 2.0, and 4.0 ma. The major results were as follows: (a) Chlorpromazine generated a dose-dependent decrease in both rate of appetitive responding and per cent avoidance responses. (b) Shock intensity did not significantly affect the rate of appetitive responses. (c) However, there was a significant Shock Intensity × Dosage interaction for avoidance responding. When compared to appetitive responding, chlorpromazine may effect a greater or lesser suppression in avoidance responding depending upon the intensity of shock maintaining the avoidance response.

Punishment of an extinguishing shock-avoidance response by time-out from positive reinforcement.

Two experiments were conducted to determine the effects of punishment by time-out from positive reinforcement on the extinction of discriminated shock-avoidance responding. Subjects were trained initially to bar press for food on an intermittent schedule of reinforcement and, concurrently, to avoid shock at the onset of a warning signal. Experiment I compared avoidance extinction performance under no punishment and when avoidance responding resulted in a 30-sec TO from reinforced appetitive responding. In Exp II, the contingent use of TO punishment was compared with its random, or noncontingent use. The results of both experiments showed that in the absence of punishment, avoidance extinction was characterized by short latencies and nearly 100% avoidance responding. Avoidance responding in extinction was little affected by noncontingent TO punishment. When TO was made contingent upon avoidance responding, however, avoidance latencies immediately increased and the frequency of avoidance responses subsequently decreased to zero.