"Warmup" and "cooldown" in Sidman avoidance behavior of rats: A dual-process interpretation

The present experiment investigated relations between "warmup" in unsignalled Sidman avoidance in rats and the intensity of shock. Magnitude of shock-rate change was quantified by comparing the rat's behavior during the initial third and the final two thirds of the same session. Warmup was said to occur whenever the shock rate during the initial 20 min was higher than the shock rate during the final 40 min of a 60 min session. "Cooldown" was defined as lower shock rate during the initial 20 min than during the final 40 min. Warmup was observed when shocks were intense, cooldown was observed when shocks were low intensity, and neither was observed when medium-intensity shocks were administered. Response-rate changes were correlated with shock-rate changes, but were smaller. The results are interpreted within the framework of a dual-process theory of habituation.     

Conditioned-aversive aspects of electric shock

Two experiments were reported in which it was observed that a weak shock became more aversive as a result of appropriate pairing of that stimulus with a stronger shock. The enhanced aversiveness of the weak shock was reflected in Experiment 1 by an apparent increase in the reinforcement provided by response-contingent termination of that shock. In Experiment 2, the weak shock was observed to be more suppressive of a consummatory-response baseline following appropriate pairings of the weak and strong shocks. The results of these studies were discussed in terms of their implications for certain aversive-conditioning situations in which shocks may serve, in part, as conditioned stimuli.     

Group aversion by imaginal, vicarious and shared recipient-observer shocks

Sixty college students completed waiting control or alternative group aversion conditions, matched for severity and chronicity of nail-biting. Treatments spanned four sessions. Imaginai aversion (covert sensitization) clients visualized shocks to themselves. Vicarious aversion clients observed shocks to a trained model. A ‘hotseat’ format randomized a few actual shocks to each client with observing peers shocked on remaining trials. The predominant pattern of outcome and subjective impact results was as follows: Hotseat consistently best; vicarious typically second; imaginal usually third; controls worst. Clinical and conceptual issues are raised.     

Variable-interval escape from stimuli accompanied by shocks

Individual performances of three rats were examined under a procedure in which steady rates of bar pressing were maintained by conditioned aversive stimulation. Originally neutral visual and auditory stimuli were accompanied by widely and irregularly spaced pulses of shock; they were terminated on a variable-interval schedule by pressing a bar. The contingencies between behavior and shock were also duplicated in a control procedure in which no visual or auditory stimuli were provided. Pressing observed under the control procedure was attributed to differences in the aversiveness of pressing and nonpressing behavior engendered by differences in the incidence of shock following the two classes of behavior. Increased rates with visual and auditory stimuli were attributed to termination of conditioned aversive stimulation. Control rates declined more rapidly than did experimental rates as the mean interval between successive shocks was lengthened; both rates tended to decline when less than 60 sec was allowed as time out from shocks following the successful response. In the control procedure, discrimination between the continuation and discontinuation of the shock series, as measured by relative rates, depended on the relative length of the interval between shocks and the time-out period. Regular warm-up accelerations in rate were noted following an initial delay in responding at the beginning of each session. The length of time required for the warm-up depended on the length of the mean interval between shocks, indicating that exposure to a certain amount of shock was required to establish a supporting state for the observed performance.     

Density and delay of punishment of free-operant avoidance

In two experiments, the free-operant shock-avoidance behavior of rats was punished by electric shock. Two aspects of the schedule of response-produced shock were varied: the frequency of punishment over time (punishment density) and the temporal interval between the punished response and the punishment (punishment delay). The general finding was that response-produced shock suppressed avoidance responding under most of the density-delay combinations studied, and suppression increased as a function of increases in density and decreases in delay. Rate increases of small magnitude also were observed, usually as an initial reaction to the lesser densities and longer delays. Response suppression, while decreasing the number of punishment shocks received, also increased the number of avoidance shocks, so that the total number of shocks received usually was greater than the minimal number possible. The results were discussed from the standpoint of similarities between the effects of punishing positively and negatively reinforced behavior. The finding that subjects did not minimize the total number of shocks suggested that when avoidance behavior is punished, responding is controlled more by the local consequences of responding than by overall shock frequencies during the course of the session.     

Imitation of Self‐Aggressive Behavior: An Experimental Test of the Contagion Hypothesis1

The purpose of the present study was to experimentally examine the influence of a self‐aggressive model on self‐aggressive behavior under controlled laboratory conditions. Participants (N= 94) were given the opportunity to self‐administer electric shock while competing with a fictitious opponent in a reaction‐time task. Participants observed the opponent self‐administer either increasingly intense shock (a self‐aggressive model) or constant low shocks (a non‐self‐aggressive model). Self‐aggression was defined as the intensity of shock that was self‐administered by participants. Results provide support for the notion that social information can influence the expression of self‐aggressive behavior. Specifically, participants attended to the opponent's shock choices in both model conditions, and chose shocks consistent with those of the observed model.     

Effects of a stimulus associated with a victim's pain on later aggression.

Male college students participated in an experiment designed to associate a neutral stimulus with a victim's pain and then to assess the impact of the paired stimulus on their aggression. The subjects were either provoked or not provoked by a confederate's shock evaluation. They then observed a flashing white light that was associated with either their former evaluator's pain or an irrelevant, affectively neutral event. The subjects then administered electric shocks to a different confederate, with whom they had not interacted previously, at the flash of both the familiar white light (the conditioned stimulus) and a novel blue light. Results supported the prediction that provoked subjects would give more intense shocks to the conditioned stimulus when it had been associated with their evaluator's pain. Unprovoked subjects were found to give less intense shocks to the light that had been associated with their evaluator's pain.     

Effects of viewing real versus fantasy violence upon interpersonal aggression

Of 96 male undergraduates, one-third saw a violent film which they were told represented a real event, one-third saw the same film presented as a fictional event, and the remaining subjects saw no film. One-half of the subjects in each group had been attacked previously by a confederate while the others had not. Each subject was then given an opportunity to aggress against the confederate by administering shocks to him as punishment in a learning task. Results indicate that subjects who observed real violence delivered stronger shocks to the confederate than subjects who viewed fantasy violence or saw no film. Subjects who were angered and saw the real film were the most punitive toward the confederate.     

Painfulness decreases the discriminability of electric shock

Two experiments were designed to investigate the relation between the reported painfulness and the discriminability of pairs of electric shocks for which the ratio between the higher and the lower intensity was held constant. In both experiments, subjects first gave category ratings of the painfulness of single shocks in the range 40 to 4.8 mA. Then, in a discrimination experiment, they were required to identify the stronger of a pair of intensities presented in succession. The proportion of correct responses (Experiment 1) or the proportion of area under the receiver operating characteristic (Experiment 2) increased between a low-intensity pairing and a medium-intensity pairing and decreased between a medium-intensity pairing and a high-intensity pairing for subjects who rated the highest intensities as strongly painful. Subjects who gave moderate- or weak-pain ratings for the high-intensity shocks showed no significant increase or decrease in accuracy between the medium- and high-intensity pairings. Time-order errors were observed in Experiment 1. The proportion of trials on which the second stimulus of the pair was identified as the stronger increased monotonically as a function of stimulus magnitude. The results are discussed in the context of psychological assessment of analgesic procedures.     

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.     

Relative effectiveness of concurrent forward/backward versus simple forward and simple backward Pavlovian conditioning procedures

Concurrent forward/backward Pavlovian conditioning procedures were compared with simple forward and simple backward procedures for differential excitatory and inhibitory conditioning. Four groups of dogs each received 30 shocks while restrained in a Pavlovian harness. One group of dogs (CON) received concurrent conditioning with a clicker signaling shocks and with a tone following shocks. For another group of dogs (SF), a clicker signaled the shocks, whereas the tone was randomly related to shocks. For a third group (SB), the tone followed shock termination, whereas the clicker was randomly related to shocks. For a fourth group (TRC), both the clicker and the tone were randomly related to shocks. All stimuli were then superimposed on a temporally paced avoidance baseline and their associative properties were assessed relative to the TRC group. Differential excitatory-inhibitory conditioning was significantly reduced in the concurrent procedure relative to that which occurred in the simple conditioning procedures despite exactly equal CS + -US and US-CS-contingencies. These results were interpreted with reference to contextual conditioning effects predicted by the Rescorla-Wagner conditioning model and the theoretical issue of independence vs. interdependence of CS-US associative strengths.     

Persistent shock-elicited responding engendered by a negative-reinforcement procedure

A procedure in which responses reduced intermittently presented electric shocks to one quarter of their originally scheduled intensity, effectively engendered and maintained lever pressing in hooded rats. This contingency also markedly increased the response rates of rats initially trained under an unsignaled avoidance procedure. The responding of all animals extinguished rapidly when shock was withdrawn. Subsequently, it was discovered that high response rates could be maintained solely through presentation of shocks that were not affected by responses. Variations in the interval between shocks and changes in shock intensity over a wide range did not attenuate responding. Terminal performance was characterized by a consistent pattern of shock-elicited responses. Responses were also elicited by a tone following repeated tone-shock pairings. Finally, responding that was maintained by response-independent shocks was quickly suppressed by response-contingent shocks of the same intensity.     

Behavioral contrast during multiple avoidance schedules

Changes were observed in the rate of avoidance responding in both components of a multiple schedule of Sidman-avoidance after the shock frequency was changed in only one component. The rate change in each component was positively correlated, in direction and magnitude, with the change in the relative rate of reinforcement (percentage of total shocks) in that component.     

Characteristics and response-displacement effects of shock-generated responding during negative reinforcement procedures: pre-shock responding and post-shock aggressive responding

Bar-pressing (Experiment I) or key-pressing (Experiments II and III) responses of monkeys were reinforced according to a fixed-interval schedule of negative reinforcement: the first response after a fixed interval of time terminated regularly spaced shocks for a fixed time designated as the reinforcement period. During extinction, shocks continued during the reinforcement period. That there were two types of responding generated by shock alone was indicated by (1) the level of responding maintained during extinction relative to conditions without shock, (2) the stability of two between-shock response patterns across reinforcement and extinction conditions, and (3) the development of these two between-shock patterns without a history of reinforcement. Subjects developed either a pre-shock or a post-shock response pattern when only the bar was available. However, when both a bite tube, an operandum requiring an aggressive topography, and a recessed key, an operandum that did not require an aggressive topography, were provided, the post-shock pattern was observed in tube biting and the pre-shock pattern was observed in key pressing. Removal of the bite tube produced post-shock key responding similar to that observed when only the bar was available. The displacement of post-shock, aggression-motivated responding confirmed the confounding effect of shock-generated responding in negative reinforcement procedures, and suggests that the use of concurrent response alternatives would reduce such confounding.     

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.     

Responding under schedules combining response-dependent and response-independent shock delivery

Lever pressing of three squirrel monkeys with experience under continuous avoidance schedules was maintained by response-produced shock under a 5-minute variable-interval schedule. Responding decreased when half of the scheduled shocks were delivered independently of lever pressing and decreased further when all shocks were independent of lever pressing. Responding was lowest when all shocks were eliminated. When the proportion of response-dependent shocks increased, responding increased. This relation occurred even though the frequency and temporal distribution of shock delivery remained the same. Responding of two monkeys increased in a graded fashion as the frequency of shock was increased by arranging variable-time 5-minute, 2-minute, and 1-minute schedules jointly with the variable-interval 5-minute schedule. Thus, increasing the proportion of response-independent shocks decreased responding when the overall frequency of shocks stayed the same, but increased responding when the overall frequency of shock delivery increased.     

Elicitation and punishment of intraspecies aggression by the same stimulus

Fighting responses were elicited in pairs of rats by shocks over a period of 46 days. During certain blocks of these days, “punishing” shocks were made contingent on the shock-elicited fights. Fighting frequency was reduced as a direct function of the intensity of the contingent shocks. Fighting frequency recovered completely when contingent shocks were removed.     

Fixed-interval punishment of running in hamsters

Four hamsters received brief electric shocks contingent upon running in a wheel. The fixed interval between shocks was varied systematically from 0 to 60 sec. Time spent running was directly related to the length of the fixed interval, while running speed remained roughly constant. Running depended on the fixed interval between shocks in the same way as bar-pressing maintained by food reinforcement, despite the fact that running was not established with nor maintained by explicit reinforcement.     

Actual versus potential shock in making shock situations function as negative reinforcers

The relative importance of potential and actual shocks in making shock situations function as negative reinforcers was studied. Shocks were scheduled to occur at the same rate during two stimuli. During one, squirrel monkeys could avoid the shocks; during the other, they were unavoidable. For the two stimuli the potential rate of shocks was the same, but the actual rate was lower during avoidance because of avoidance responding. Fixed-ratio responding was maintained by the change from unavoidable shock to avoidance, indicating that the change was reinforcing when it resulted in a reduction in actual shock rate with no reduction in potential shock rate. Further increases in the rate of potential shock during avoidance had little effect upon the fixed-ratio responding until the rate was increased to the point that the actual shock rate during avoidance was comparable with that during unavoidable shock. At that point, the fixed-ratio response rate decreased nearly to zero. These findings show that actual shocks are more important than potential shocks in determining whether or not a shock situation will function as a negative reinforcer; this explains why the change from unavoidable shock to avoidable shock is reinforcing.     

The release of catecholamines by shocks and stimuli paired with shocks

One monkey and five baboons were surgically prepared so that heart rate and blood pressure could be monitored continuously, and an extra-corporeal blood path was established to detect the secretion of epinephrine (adrenaline) and norepinephrine (noradrenaline). A respondent conditioning procedure was used in which a tone was paired with electric shocks. Epinephrine, but not norepinephrine was released by shocks, and a corresponding release was demonstrated by the tone alone. Heart rate and blood pressure changes were also elicited by shocks and by the tone.