Attack, avoidance, and escape reactions to aversive shock

Aversive stimuli are known to produce the behaviors of both escape and attack. The interaction between these two basic reactions was studied with rats and monkeys using many shock-escape and shock-avoidance procedures. All procedures produced attack if a target was present, the attacks occurring shortly after shock delivery. The number of attacks during escape or avoidance was a direct function of the number and duration of shocks received. Consequently, any aspect of the procedure that produced many shocks also produced many attacks such as initial acquisition, extinction, or an increase of the response requirement for escape. The escape tendency acquired prepotency over the tendency to attack since successful escape eliminated attack behavior. The attack tendency retarded escape behavior only during acquisition when the preoccupation with attack precluded the opportunity to learn the escape response. This mutual interference of escape and attack was eliminated when the attack and avoidance tendencies were combined by using biting attack as the shock-avoidance response. The result was unusually rapid conditioning of the biting-attack response. These interactions indicate that both the attack and escape tendency should be considered whenever aversive stimulation is delivered.     

Pharmacological dissociation of memory: anisomycin, a protein synthesis inhibitor, and leupeptin, a protease inhibitor, block different learning tasks

Inhibition of protein synthesis by anisomycin for a short duration impairs memory of a one-trial inhibitory avoidance task in rats. Memory of escape conditioning involving eight trials is disrupted only if the duration of protein synthesis is prolonged by repeated injections. In marked contrast, olfactory memory of rats trained on two odor discriminations is not affected by anisomycin even if the duration of inhibition is prolonged and the number of trials is reduced to a minimum. In previous work, leupeptin, a thiol proteinase inhibitor, was shown to impair olfactory discrimination learning, but left inhibitory and avoidance conditioning intact. Together, these results provide a pharmacological double dissociation of memory, and suggest that the same chemistries, or mixtures of chemistries, may not be involved in all types of memory.     

Leupeptin, a thiol proteinase inhibitor, causes a selective impairment of spatial maze performance in rats

The effects of chronic intraventricular infusion of leupeptin, a potent inhibitor of thiol proteinases, were tested on ingestive behaviors, escape and avoidance conditioning, and spatial memory in rats. The drug did not detectably influence feeding, drinking, body temperature, or the latency to escape from a mild footshock or inhibitory avoidance behavior. However, rats treated with leupeptin made numerous errors ( reentries ) in an eight-arm spatial maze. These results are interpreted as supporting the hypothesis that calcium-activated thiol proteinases are involved in the formation of certain types of memory.     

Response cost and the aversive control of human operant behavior

The effects of cost (point-loss per response) upon human avoidance, escape, and avoidance-escape behavior maintained by PLPs (point-loss periods) were investigated. Cost had a marked but differentially suppressive effect upon responding under all schedules. The greatest number of PLPs taken under cost occurred on the escape schedule. In most instances PLPs were more frequent on the avoidance-escape schedule than on the avoidance schedule under cost. Inferior avoidance performance appeared only under cost conditions. Under no-cost, all subjects (Ss) successfully avoided all PLPs after the first hour of conditioning. These results indicate that the development and maintenance of human avoidance and escape behavior may, in part, be dependent upon response cost conditions. Aversive control of human operant behavior may be limited without an adequate specification of response-cost conditions.     

Negative reinforcement as shock-frequency reduction

Is a conditioned aversive stimulus necessary in avoidance conditioning? Or is a reduction in the rate of aversive stimulation alone sufficient to generate and maintain an avoidance response? Rats were subjected to an avoidance procedure in which shocks occurred randomly in time, but a response could reduce the overall rate of shock. Fifteen acquisition curves, obtained from 16 animals, showed both immediate and delayed, rapid and gradual increases in response rate; there was no representative acquisition curve. Response rates were directly related to the amount by which the response reduced shock frequency. In extinction, when shock rates were not affected by responding, the response total was inversely related to the amount by which the response had reduced shock frequency during prior conditioning, with as many as 20,000 extinction responses when the shock frequency reduction had been relatively small. Responding on this procedure shows that avoidance conditioning can occur without benefit of either classical exteroceptive stimuli or covert stimuli inferred from the temporal constancies of a procedure. It also shows that reduction in shock rate is alone sufficient to maintain avoidance.     

Learning strategies during fear conditioning

This paper describes a model of fear learning, in which subjects have an option of behavioral responses to impending social defeat. The model generates two types of learning: social avoidance and classical conditioning, dependent upon (1) escape from or (2) social subordination to an aggressor. We hypothesized that social stress provides the impetus as well as the necessary information to stimulate dichotomous goal-oriented learning. Specialized tanks were constructed to subject rainbow trout to a conditioning paradigm where the conditioned stimulus (CS) is cessation of tank water flow (water off) and the unconditioned stimulus (US) is social aggression from a larger conspecific. Following seven daily CS/US pairings, approximately half of the test fish learned to consistently escape the aggression to a neutral chamber through a small escape hole available only during the interaction. The learning curve for escaping fish was dramatic, with an 1100% improvement in escape time over 7 days. Fish that did not escape exhibited a 400% increase in plasma cortisol and altered brain monoamine response to presentation of the CS alone. Elevated plasma cortisol levels represent classical fear conditioning in non-escaping fish, while a lack of fear conditioning and a decreased latency to escape over the training period in escapers indicates learned escape.     

Signaled avoidance in the eye withdrawal reflex of the green crab

Learning in a signaled avoidance procedure was studied in the eye withdrawal reflex of the green crab, Carcinus maenas. A puff of air to the eye, which causes eye retraction, was used as the unconditioned stimulus (US). A mild vibration on the carapace, which has no effect on untrained animals, was used as a warning (conditioned) stimulus (CS). Eye withdrawal during the CS led to the omission of the otherwise scheduled US. Acquisition was rapid, reaching about 75% avoidance after 30 trials. Extinction occurred slowly over the course of 40 CS-only trials. Yoked controls did not perform as well. The behavior of experimental animals in the avoidance procedure was found to be essentially identical to the performance of animals subjected to a classical conditioning paradigm in which CS responses had no effect on US presentation. Additional groups of animals were subjected to experiments in which (a) avoidance conditioning (60 trials) was followed by classical conditioning (40 trials) or (b) classical conditioning was followed by avoidance. The behavior of these groups was, again, essentially identical. The results suggest that there may be an underlying Pavlovian mechanism for the learned response, although the contribution of an operant process is not excluded. The results expand the range of invertebrate animals in which fundamental conditioning phenomena can be demonstrated, and may provide a neuronal model for learning in a signaled avoidance procedure.     

Effects of partial avoidance and punishment contingencies on shuttlebox-avoidance learning in Fischer 344 rats

An unsignaled, escapable shock was presented contingent on an avoidance response. Fischer 344 rats responded less to the warning signal in proportion to its temporal distance from the avoidance response. Partial contingency effects were further obtained by variation in the instrumental conditioning space for an aversive stimulus. However, the arbitrary omission of an imminent shock on half the trial in which the rats failed to avoid a shock, led to little avoidance acquisition, and shock-frequency reduction was thus not sufficient to produce the acquisition of the avoidance response. Because early avoidance responses were initiated by escape from shock, a stimulus contingency may be essential for response initiation, and an explicit response contingency is important in maintaining successful avoidance responses.     

Emotionality in selectively bred strains of rats mediates prior shock effects on escape-avoidance conditioning.

Rats of the Maudsley Reactive and Maudsley Non-reactive strains were given 25 trials of escape-avoidance conditioning after exposure to inescapable shock. Prior shock exposure (PSE) did not affect avoidance or escape latencies, but decreased the number of avoidances made by the Maudsley non-reactive animals and increased the number of their failures to escape. The results are interpreted as demonstrating an interference with the classical conditioning of a conditioned emotional response, through a reduction in the information content of the CS following PSE. The strain differences are interpreted as due to the non-reactive animals being especially sensitive to PSE.     

Role of intertrial interval following an escape or avoidance response in bar-press avoidance

In three experiments, rats learned bar-press avoidance as a function of the intertrial interval following an escape or an avoidance. The general hypothesis is that the length of these intervals affects bar-press avoidance differentially, depending on whether an avoidance follows an escape (avoidance/escape) or an avoidance (avoidance/avoidance) on the previous trial. Specifically, it is proposed that short escape ITIs will facilitate avoidance/escape and avoidance/avoidance, while avoidance ITIs will have no effect on avoidance responding. The results tend to support this hypothesis. The shorter the intertrial interval following an escape, the higher the probability of both measures: avoidance/escape and avoidance/avoidance. No effect of avoidance interval was found on avoidance/avoidance. Unpredictedly, however, it was found that in comparison to a very short intertrial interval following an avoidance (0.5 sec), relatively long intervals (5 and 45 sec) facilitate avoidance/escape. These results were interpreted as mainly reflecting nonassociative factors such as shock-produced activity.     

Prior exposure to inescapable electric shock in rats affects extinction behavior after the successful acquisition of an escape response

In Expt 1, rats exposed to 64 inescapable electric shocks in a restrainer or merely restrained were later given either 0, 5, 15 or 30 escape/avoidance training trials with a two-way shuttlebox procedure that does not lead to interference with escape acquisition due to prior exposure to inescapable shock. After escape training all rats were given an escape/avoidance extinction procedure in which shock was inescapable. The rats which had received prior exposure to inescapable shock responded less often and with longer latencies in extinction than did the restrained rats. Experiment 2 demonstrated that this effect is caused by the inescapability of the initial shock treatment. These results were explained in terms of (a) associative interference which minimized the effect of shuttlebox escape training for the preshocked subjects, and (b) a stronger tendency to recognize the presence of an inescapable shock situation during extinction for the preshocked subjects. The relationship between these results and previous work demonstrating that exposure to the escape contingency mitigates the effects of inescapable shock exposure was also discussed.     

Aversive CS control of instrumental avoidance as a function of selected parameters and method of Pavlovian conditioning

Effects of aversive CSs upon dogs' instrumental avoidance responding were assessed as a function of the Pavlovian conditioning parameters using off-baseline (Experiment 1) and on-baseline (Experiment 2) conditioning procedures. In each experiment, three UCS intensitites (2, 6, and 10 mA) were crossed factorially with two CS-UCS intervals (10 and 90 sec) yielding six groups. After 4 days of conditioning, the CS-produced effects on avoidance were determined primarily by an interaction between Pavlovian procedure (off- versus on-baseline) and UCS intensity. With off-baseline conditioning, CS-produced facilitation of avoidance was an increasing function of the UCS intensity. However, with on-baseline conditioning, only the CS paired with weak UCS facilitated avoidance, and the CS paired with the strong UCS suppressed responding. This reversing parametric function poses problems for two-process motivational theories of avoidance.     

Escape from fear: a detailed behavioral analysis of two atypical responses reinforced by CS termination

Escape from fear (EFF) is a controversial paradigm according to which animals learn to actively escape a fear-eliciting conditioned stimulus (CS) if the escape response (R-sub(e)) is paired with CS termination. Some theories posit that EFF learning is responsible for instrumental avoidance conditioning. However, EFF learning has typically been weaker than avoidance learning and difficult to reproduce. The authors examined EFF learning and memory with 2 atypical R-sub(e)s: rearing and nose-poking. The data suggest that rearing, but not nose-poking, can be learned as an instrumental EFF response. Further, EFF memory was response specific, aversively motivated, and controlled by the CS. Successful EFF learning also resulted in better long-term elimination of a passive fear reaction (freezing). Factors important for EFF experiments and theoretical considerations are discussed.     

An experimental analysis of aversive imagery versus electrical aversive conditioning in the treatment of chronic alcoholics

A series of three experiments is described comparing an aversive imagery and an electrical escape conditioning procedure in the treatment of chronic alcoholics. Treatment effects were objectively measured by recording subjects' alcohol consumption in a semi-naturalistic laboratory setting. In contrast to conventional group outcome studies, the use of single-subject methodology provided a fine-grained analysis of individual response patterns. The aversive imagery and escape conditioning methods did not differ from each other, and were relatively ineffective in suppressing alcohol intake. In contrast, a punishment procedure in which shock was contingent on drinking did effectively suppress drinking. The data suggest that alcoholics can control their drinking by self-administered shock. The implications for the analysis and treatment of alcoholics are discussed.     

Measurement of fear of the conditioned stimulus and of situational cues at several stages of two-way avoidance learning

In Experiment 1, subjects were trained in a signaled two-way avoidance task to a criterion of either 2, 10, or 20 consecutive avoidance responses. Subsequently, they were allowed to escape, in the absence of shock, from one compartment of the avoidance apparatus to an adjacent safe box. For one group at each criterion level, the conditioned stimulus (CS) was presented during these trials; for another group, it was not (NCS). The rate and level of learning of the escape response were taken to reflect the amount of fear of the CS and situational cues present at the end of avoidance training for the CS groups and the amount of fear of the situational cues alone for the NCS groups. Under the CS condition, all groups learned equally well; under the NCS condition, learning occurred only in the two-criterion group. This pattern of results suggests that, as avoidance training continued, differential reinforcement led to the formation of a discrimination so that a substantial amount of fear was elicited by the CS plus situational cues but only a minimal amount by the situational cues alone. Such a loss of fear of situational cues would, according to effective reinforcement theory, serve to maintain or even increase reinforcement as avoidance training progressed. The results of Experiment 2, by ruling out some alternative explanations, supported the interpretation that the learning of the instrumental escape response in the first experiment was based on prior fear conditioning.     

Conditioning history and the control of human avoidance and escape responding

Inter-subject differences in response rates under free-operant avoidance and escape schedules are commonly obtained from humans. Data are presented which demonstrate that such differences can be controlled experimentally by giving subjects different conditioning histories. Subjects given a fixed-ratio history avoided and/or escaped from “point-loss periods” at higher rates than subjects given a differential-reinforcement-of-low-rates history. History related differences in response rates were maintained during 40 hr of escape responding. For low-rates history subjects, response rates under escape contingencies decreased as the rate of point-loss periods decreased.     

Hearing Impairment, Coping Strategies, and Anxiety Sensitivity

The aim was to study coping strategies among hearing-impaired individuals by using a validated coping instrument—The Ways of Coping Questionnaire (WOCQ; S. Folkman & R. Lazarus, 1988)—and to relate the use of coping with anxiety sensitivity and experience of hearing impairment. A questionnaire booklet was sent out to the members of the local branch of the Swedish Hard of Hearing Association. Ninety-four members responded to the questionnaire, yielding a 53% response rate. Primary outcome measures were the WOCQ, the Anxiety Sensitivity Index, and visual analogue scale rating of discomfort from hearing impairment. Repeated measures analysis of WOCQ subscales showed that the participants used planful problem solving and self-controlling coping strategies whereas escape/avoidance responses were less frequently used than the other coping strategies. Anxiety sensitivity was associated with escape/avoidance coping (r = .63, p < .0001). In conclusion, hearing-impaired individuals do not use escape/avoidance coping more than other coping strategies. However, escape/avoidance coping is associated with anxiety sensitivity, suggesting that sensitivity to anxiety sensations is an important associated factor. Coping strategies were not associated with discomfort from hearing impairment in any meaningful way.     

Classical conditioning of goldfish in the shuttlebox

Goldfish trained in a shuttlebox with light as CS and brief shock as US acquire the shuttling response to light whether or not an avoidance contingency is in effect. That the change in behavior produced by the classical procedure is not due merely to sensitization is demonstrated by a discriminative control. The results suggest the usefulness of the shuttlebox for the study of classical conditioning in goldfish and call into question the instrumental interpretation of the change in behavior produced by the avoidance procedure.     

Operant conditioning of autobiographical memory retrieval

Functional avoidance is considered as one of the key mechanisms underlying overgeneral autobiographical memory (OGM). According to this view OGM is regarded as a learned cognitive avoidance strategy, based on principles of operant conditioning; i.e., individuals learn to avoid the emotionally painful consequences associated with the retrieval of specific negative memories. The aim of the present study was to test one of the basic assumptions of the functional avoidance account, namely that autobiographical memory retrieval can be brought under operant control. Here 41 students were instructed to retrieve personal memories in response to 60 emotional cue words. Depending on the condition, they were punished with an aversive sound for the retrieval of specific or nonspecific memories in an operant conditioning procedure. Analyzes showed that the course of memory specificity significantly differed between conditions. After the procedure participants punished for nonspecific memories retrieved significantly more specific memories compared to participants punished for specific memories. However, whereas memory specificity significantly increased in participants punished for specific memories, it did not significantly decrease in participants punished for nonspecific memories. Thus, while our findings indicate that autobiographical memory retrieval can be brought under operant control, they do not support a functional avoidance view on OGM.