Experimental self-punishment and superstitious escape behavior

Rats were trained to escape from shock by pressing a bar. Bar holding was subsequently punished with very brief shocks. This treatment failed to depress bar-holding behavior. In some cases, although the escape shocks were delivered very infrequently, bar holding was maintained and resulted in the delivery of several thousand punishments per session. These and other effects of the punishment treatment were investigated. Finally, some of the possibilities of superstitious escape responding were explored by presenting inescapable shocks to rats that had been trained to escape shock by lever pressing. Although responding during these shocks had no programmed consequences, responding was sustained.     

Learned helplessness in the rat.

Four experiments attempted to produce behavior in the rat parallel to the behavior characteristic of learned helplessness in the dog. When rats received escapable, inescapable, or no shock and were later tested in jump-up escape, both inescapable and no-shock controls failed to escape. When bar pressing, rather than jumping up, was used as the tested escape response, fixed ratio (FR) 3 was interfered with by inescapable shock, but not lesser ratios. With FR-3, the no-shock control escaped well. Interference with escape was shown to be a function of the inescapability of shock and not shock per se: Rats that were "put through" and learned a prior jump-up escape did not become passive, but their yoked, inescapable partners did. Rats, as well as dogs, fail to escape shock as a function of prior inescapability, exhibiting learned helplessness.     

Escape behavior under different fixed ratios and shock intensities

The effects of ratio length and shock intensity on bar pressing were examined in three rats in two escape-from-shock experiments. In Experiment I, shock intensity was held constant while the schedule was varied from FR 1 to FR 20. The latency of the first escape response increased with FR length while the escape rate, computed as over-all rate in shock minus latency of the first response, decreased at FR 20. In Experiment II, the schedule was held constant at FR 5 while shock intensity was manipulated. Latency decreased as intensity increased, while escape rate increased with intensity, passing through a maximum for two subjects. Responses occurring during the last 100 sec of the 2-min escape period decreased as the FR increased for all subjects, and decreased as shock intensity increased for two subjects.     

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.     

Tolerance of pain as a measure of fear

Fear thresholds were measured in four experiments by exposing rats to electric shock in order to determine the maximal intensity rats would tolerate rather than enter a fear-arousing box and/or stop freezing. Increasing fear raised these thresholds. They were greater for rats having to escape shock to a fear-arousing box than for rats having to escape shock and fear to a neutral box. The forgetting functions for the latter two groups differed: the first group yielded a monotonic decay function, whereas the second group yielded an inverted U-shaped function. These thresholds decreased as a function of an avoidance learning procedure. Rats that had to escape shock to a fear arousing box did not do so immediately, although they had stopped freezing. An avoidance-avoidance conflict explanation for immobility was not found to be valid. A theoretical formulation based on the following two hypotheses was suggested to explain these results: the fear-aroused freezing (immobility) is an unlearned response; finding a way to escape the source of fear starts another unlearned response, withdrawal.     

The effects of escape conditioning and shock intensity on responding during inescapable shock

Eight albino rats, conditioned to press a lever to escape shock, continued to lever press during short inescapable shocks presented subsequently. The rate of this behavior was found to be higher for higher shock intensities regardless of the order in which shock values were presented. Relative to the immediately preceding escape rate, responding during inescapable shock was higher following conditioning at higher fixed-ratio escape requirements. Four subjects not conditioned to escape shock pressed the lever very infrequently during inescapable shock and showed little change with changes in shock intensity. The escape conditioning effects suggest that responding during inescapable shock is superstitious escape behavior. The effects of shock intensity on this behavior appear to be similar to reported effects of shock intensity on escape behavior.     

Catecholamine depletion in mice upon reexposure to stress: mediation of the escape deficits produced by inescapable shock

Immediately following exposure to 60 inescapable shocks, Swiss-Webster mice had significantly reduced hypothalamic norepinephrine (NE). Within 24 hr NE levels returned to control values. Reexposure to as few as 10 shocks 24 hr after initial stress exposure resulted in a significant decline of hypothalamic NE. Moreover, at this interval after inescapable shock, escape performance was severely disrupted, with a large proportion of mice exhibiting numerous failures to escape shock. Increasing brain dopamine (DA) and NE by L-dopa treatment prior to inescapable shock prevented the escape deficits. Conversely, pairing five inescapable shocks with NE depletion by FLA-63, or both DA and NE depletion by alpha-methyl-p-tyrosine, disrupted escape performance 24 hr later. Residual drug effects, state dependence, or sustained amine turnover could not account for the behavioral changes observed. Data are discussed in terms of catecholamine mediation of escape performance through variations in response maintenance abilities. Furthermore, it is suggested that the long-term effects of inescapable shock may be due to sensitization effects or conditioned amine depletion.     

Rats learn the relationship between responding and environmental events: An expansion of the learned helplessness hypothesis

Previous research has shown that preexposure to inescapable shock interferes with subsequent acquisition of escape responding, while pretraining with escapable shock facilitates subsequent acquisition of a different escape response. It has also been demonstrated that interference and facilitation persist when the aversive event is changed between the two phases of training. The present experiment extended these findings, showing generalized learning from an appetitive to an aversive situation. Six groups of rats received the following treatment in the presence of discriminative stimuli: One group was trained to nose press for food, a second to chain pull for food, and a third to chain pull to escape or avoid shock. Two groups received either signalled free food or inescapable shock, and a naive control group received no pretreatment. All groups were then tested in a nose-press escape-avoidance situation. The three groups with prior response training acquired responding most rapidly, and at the same rate. The naive controls acquired responding slowly, and the two groups with response-independent histories did not acquire responding during the 5 days of training. It was concluded that rats learn the relationship between responding and environmental events and that such learning strongly influences subsequent learning.     

Behavioral assessment of pain detection and tolerance in monkeys

Cebus albifrons monkeys received electrical stimulation of the hindlimbs over a wide range of intensities. On trials signalled by a blue light, the animals were permitted to escape shock by pressing a disc, or shock was terminated after 8 sec (free escape). Escape force (disc pressure) was found to increase as stimulation intensity increased well beyond escape threshold, while shock duration curves reached plateau at the mid-range of intensities. The shock duration curves generated by free escape responses should be comparable to pain detection functions obtained by similar operations in humans, and the curves were stable over months of testing, as is generally found in pain-detection studies. On trials signalled by a red light, the animals received intense tail shock immediately after escape responses (punished escape), or, if they endured leg shock for 8 sec without escaping, then they could avoid tail shock with a panel press. The shock duration curves generated by punished escape responses should be comparable to pain tolerance functions as defined for human subjects, and the escape thresholds were considerably higher on red-light trials. As in human studies, the tolerance curves were not stable over repeated testing sessions, and some feature of the paradigm forced a progression toward extremely high levels of tolerance.     

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.     

Escape responding in a shuttlebox

Measures of response latency are a primary tool for those who investigate escape responding in rats. Unfortunately, the single term “latency to escape” has been applied to several different measures of latency. The present study was designed to demonstrate that two different measures of the “latency to escape” tap different aspects of escape responding. To that end, rats were given escape training using a Sidman Avoidance Schedule with brief inescapable electric shock as the aversive stimulus. The latency to escape the shock-shock interval, as measured from the onset of the last shock in a shock period, did not change across trials. However, the latency to escape the shock period, as measured from the onset of the first shock in a shock period, decreased across trials. In addition, the presentation of a feedback stimulus contingent upon escape responding did not affect the latency to escape either the shock period or a shock-shock interval. The results show that these two latency measures, typically not recognized as unique, measure different characteristics of the strength of escape responding in a shuttlebox. Alternative accounts of this pattern of data were considered.     

Exposure to inescapable shock produces both activity and associative deficits in the rat

Interference with shuttle-box escape learning following exposure to inescapable shock is often difficult to obtain in rats. The first experiment investigated the role of shock intensity during escape training in the apparent fragility of the effect. Experiment 1A demonstrated that the magnitude of the interference effect was systematically related to shock intensity during shuttle-box testing. At .6 mA, a robust effect was obtained, whereas at .8 mA and 1.0, little or no deficit in the escape performance of inescapably shocked rats was observed. Experiment 1B demonstrated that the deficit observed in Experiment 1A depended upon whether or not rats could control shock offset. Experiment 2 suggested that preshock may suppress activity and that higher shock levels may overcome this deficit. Experiment 3 tested this as the sole cause of the escape deficit by requiring an escape response which exceeded the level of activity readily elicited by a 1.0-mA shock in both restrained and preshocked rats. In such a task, preshocked rats performed more poorly than did restrained controls. These results are consistent with the possibility that inescapable shock may, in addition to reducing activity, produce an associative deficit. Experiment 4 more clearly demonstrated that inescapable shock produces deficits in performance which cannot be expleined by activity deficits and which appear to be associative in nature. It was shown that inescapable shock interfered with the acquisition of signaled punishment suppression but not CER suppression. The theoretical implications of these data for explanations of the manner in which prior exposure to inescapable shock interferes with escape learning were discussed.     

Summation of pain produced in different anatomical regions*

Unescapable shock was administered to rats in a spatial preference task through pairs of electrodes implanted subcutaneously near the neck and tail. The animals were permitted to choose between shock through both pairs of electrodes or through one pair by crossing from one side of a cage to the other. Rats preferred shock in two locations to an equal amount in one location. The results indicate that summation of pain is greater when stimuli are added in the same rather than in different places.     

Absence of shock-elicited aggression in pigeons

Two pigeons that attacked a taxidermically prepared target pigeon during a schedule of positive reinforcement for key pecking, and two that did not, were shocked through implanted electrodes in the presence of the target. Shock intensities of 2 and 4 mA, durations of 0.1 and 1.3 sec, and frequencies of 2, 6, 20, and 35 per minute were delivered across 16 sessions with 180 shocks per session. No pigeon attacked the target; one pecked the shockplug on its back. The two pigeons that had not attacked during the positive reinforcement schedules were conditioned to peck the target for food reinforcement before another 16 sessions of shock. No attack was observed in these shock sessions. During subsequent positive reinforcement of key pecking, the target was attacked by the two pigeons that had originally attacked and by one that had not. Absence of shock-elicited attack in these pigeons may be related to the parameters of the experiment or may be yet another instance of the absence of shock-elicited attack in the class Aves. At least under the present conditions, it was not possible to predict the level of attack during electric shock from the level of attack during schedules of positive reinforcement for key pecking.     

Forced exercise blocks learned helplessness in the cockroach (Periplaneta americana)

For three consecutive days, two groups of adult female cockroaches (Periplaneta americana) (ns = 10) received inescapable shock. 24 hr. later one group was exposed to 10 min. of forced exercise on a treadmill while the other group received no exercise. Both groups were then run in a shuttlebox escape task. The cockroaches exposed to forced exercise did not become helpless in the shuttlebox escape task.     

Learned helplessness in the rat: time course, immunization, and reversibility.

Rats, like dogs, fail to escape following exposure to inescapable shock. This failure to escape does not dissipate in time; rats fail to escape 5 min, 1 hr., 4 hr., 24 hr., and 1 wk. after receiving inescapable shock. Rats that first learned to jump up to escape were not retarded later at bar pressing to escape following inescapable shock. Failure to escape can be broken up by forcibly exposing the rat to an escape contingency. Therefore, the effects of inescapable shock in the rat parallel learned helplessness effects in the dog.     

Reconsideration of the role of competing responses in demonstrations of the interference effect (learned helplessness)

In Experiment 1a, rats trained to escape shock by performing a 2-s inactive response were less impaired on a subsequent 2-way shuttle response than their yoked counterparts that received inescapable shock. In contrast, in Experiment 1b, rats trained to escape shock by performing a longer duration inactive response were more impaired on the subsequent escape task than their inescapably shocked counterparts. In Experiment 2, the results of Experiments 1a and 1b were replicated, and the inactive responses performed during pretreatment by both the escapable and inescapable shock groups were assessed and correlated with test stage 2-way shuttle escape performance. These activity data indicate that inactivity during pretreatment shock in both escapable and inescapable shock groups was a highly reliable predictor of subsequent 2-way shuttle performance, irrespective of the pretreatment shock contingency to which these Ss were exposed.     

Escape performance after inescapable shock in selectively bred lines of mice: response maintenance and catecholamine activity.

The effects of inescapable shock on subsequent escape performance and shock-elicited activity were examined in six lines of mice selectively bred for differences in general locomotor activity. The line differences in locomotor activity were found to be unrelated to the differences observed on shock-elicited activity. However, escape performance following exposure to inescapable shock was predictable from the levels of shock-elicited activity. Those lines that displayed the greatest decline in motor activity during shock likewise displayed the most pronounced escape deficits. The line differences in escape performance induced by inescapable shock could be mimicked by treatment with a tyrosine hydroxylase inhibitor, alpha-methyl-p-tyrosine. As predicted, the lines that displayed the least interference after tyrosine hydroxylase inhibition exhibited the smallest reduction in levels of catecholamines. The effects on escape performance following inescapable shock are interpreted in terms of the role of response maintenance deficits produced by catecholamine depletion.     

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.