Long-Term conditioned fear modification in the dog as measured by changes in urinary 11-hydroxycorticosteroids. Heart rate and behavior

Heart rate (HR), operant key pressing, and urinary 11-hydroxycorticosteroids (11-OH-CS) were recorded while dogs were subjected to various aversive conditioning schedules over a six-month period. The schedules consisted of Sidman avoidance, followed by a Sidman schedule which paired unavoidable shocks (US) with offset of seven discrete conditioned stimuli (CS). Introduction of the Sidman avoidance schedule led to an increase in HR. Changes in the experimental schedule always results in an increase in urinary 11-OH-CS. Neither HR nor urinary 11-OH-CS were correlated with rate of operant key pressing. Differences in the dependent variables reflected the different topological characteristics of the dogs studied. This study demonstrated: (a) a causal independence of physiological and behavioral responses conditioned to the same stimulus complex, and (b) that longterm increases in HR can be maintained if the experimental situation is manipulated to maintain the fear eliciting characteristics of the conditioning situation.     

Behavior analysis and revaluation

Revaluation refers to phenomena in which the strength of an operant is altered by reinforcer-related manipulations that take place outside the conditioning situation in which the operant was selected. As an example, if lever pressing is acquired using food as a reinforcer and food is later paired with an aversive stimulus, the frequency of lever pressing decreases when subsequently tested. Associationist psychology infers from such findings that conditioning produces a response-outcome (i.e., reinforcer) association and that the operant decreased in strength because pairing the reinforcer with the aversive stimulus changed the value of the outcome. Here, we present an approach to the interpretation of these and related findings that employs neural network simulations grounded in the experimental analysis of behavior and neuroscience. In so doing, we address some general issues regarding the relations among behavior analysis, neuroscience, and associationism.     

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.     

Procedure for operant conditioning of the dog

Most reports arising from operant conditioning procedures have little or no emphasis on the actual behavior shaping or acquisition phase of the responses which are the cumulative frequency of the well-practiced act. There is a need for more detail for beginners or those desiring a clearer understanding of procedures leading to the finally reported data. The procedure reported here is typically used to compare animal subjects or conditions, such as drugs, both in the acquisition and final phases of behavior. Beginning with an unconditional response (e.g. feeding) a bridging stimulus is paired in classical conditioning fashion. From that point on the bridging stimulus and UCS (feeding—or shock) are used immediately as reward or reinforcement only for responses “in the direction of the final desired behavior. The number of timed standardized behavior shaping sessions to criterion is the best index of acquisition phase performance and the total number bar presses or the rate of bar pressing (slope) is the usual index of operant responding. With timid animals it is often necessary to administer tranquilizers.     

The number of trials of compound conditioning: its effect on latent inhibition in rats.

Two experiments interspersed nonreinforced tests for the strength of the preexposed and nonpreexposed elements of a compound CS throughout conditioning. The nonreinforced exposures and the conditioning trials were superimposed on an appetitive operant baseline, and conditioned suppression of the rats' bar pressing was the dependent variable. In both experiments, the preexposed element failed to suppress responding and failed to gain strength over trials. The nonpreexposed element at first suppressed responding completely but gradually lost control of responding, even while the compound continued to suppress responding asymptotically. The results are discussed in terms of 'loss of salience' and 'discrimination' hypotheses.     

Operant modulation of low-level attributes of rule-governed behavior by nonverbal contingencies

A low-level and nonsalient attribute of behavior (i.e., speed of pressing) was subjected to differential nonverbal operant reinforcement when rules governed a high-level attribute of that behavior (i.e., counting by means of key presses). Unknown to the subjects, reinforcers depended on reduced (slow group) or increased (fast group) speed of pressing rather than on the correct number of presses. The reinforced attribute was modulated according to the arranged speed contingencies independently of the instructed task and independently of subjects' awareness of the critical contingency. A control group receiving random reinforcers demonstrated no systematic speed changes. Possible mechanisms related to behavior changes of this type were examined and discussed, and it was concluded that the behavior changes observed in this situation could be attributed to operant conditioning. The results substantiate the assumption that nonverbal operant contingencies may modulate low-level and nonsalient attributes of rule-governed behavior.     

An experimental approach to the reduction of overactive behavior

An operant, differential reinforcement procedure (DRO) was employed in a playroom setting for the purpose of controlling overactivity. Six overactive, mentally retarded children, aged 8–13 yr were first observed individually for a period of 8 days in the playroom in order to obtain a baseline performance on a specially constructed check-list of hyperactive behavior. Following this, the conditioning phase began under a fixed schedule of reinforcement with tokens as the reinforcing agents (later to be exchanged for candy). A fading-out phase was instituted after the 30-day conditioning period in order to maintain resistance to extinction at a higher level. Post-conditioning observations were then made. It was conclusively shown that the disturbed, hyperactive behavior came under stimulus control with “grasshopper” play decreasing substantially during the latter part of conditioning and extinction periods.     

Operant performance patterns of normal and nervous water-deprived dogs

Previous studies have shown that most food-deprived genetically nervous pointer dogs fail to learn a bar-pressing response for food reward and those which do learn are erratic in bar pressing compared to genetically normal pointer dogs which usually learn rapidly and perform well. Benzodiazepine drugs facilitate learning and performance of the responses in nervous dogs. The present study aimed at finding whether a stronger drive producing state, such as water deprivation, would facilitate learning and performance in even severely nervous dogs. Eight normal line and 7 nervous line dogs successfully learned to perform well a paddle-pressing response which activates a valve releasing water into a drinking pan. One disturbed dog of each line did not learn successfully. Behavior shaping was about as easy and as rapid in nervous line dogs as in normals. Nervous line dogs tended to be as consistent in responding. However, response rates of nervous line dogs averaged about two-thirds those of normal line dogs, the slowed rate of responses being taken up mostly in excessive, rather stereotyped, licking of the water pan. Response rates correlated well with degree of nervousness as measured on independent well standardized behavior tests. This behavior seems to add another dimension to the characterization of the nervousness of these “spooky” pointer dogs.     

Negative reinforcement with shock-frequency increase

Two avoidance-conditioning experiments in which responding delayed shocks are reported. Rats receiving an average of two shocks per minute (imposed condition) could produce, by pressing a bar, a 3-min alternate condition. Six (Experiment I) or more (Experiment II) shocks occurred in the alternate condition. All shocks in the alternate condition were delayed and delivered at 1-sec intervals. With long delays, all subjects produced the alternate condition and spent a large percentage of each session in the alternate condition. The first experiment demonstrated that the longer the delay from onset of the alternate condition to onset of the shocks, the more session time spent in the alternate condition. The second experiment indicated that despite increased shock frequency, behavior is acquired and maintained when responding leads to sufficient delay. Individual subjects produced the alternate condition by bar pressing in essentially one of two patterns. One pattern, termed postshock, involved bar pressing immediately after shock; the other, termed posttransition, involved responding immediately after the transition from the alternate to the imposed condition. These results indicate that shock-frequency reduction is not necessary for avoidance conditioning; delay to shock onset is sufficient.     

The rehabilitation of genetically nervous dogs

Aware that intensive efforts to rehabilitate half of split litters from a nervous strain of Pointers through daily human contact have been unsuccessful, the authors designed this study to determine if a radically different approach utilizing the natural interest for birds and hunting which most Pointers possess would be a bridge to normalcy so that dogs genetically prone to nervous behavior could be rehabilitated. Five nervous and three normal dogs approaching young adulthood were gradually desensitized to open areas, live quail, gun reports and humans—all of which usually produce catatonic freezing, hyper-startle and strong avoidance behavior in the nervous animals. Through a “naturalistic” approach in the framework of the Pointers’ non-laboratory ecological niche using graduated techniques, reciprocally competitive responses and social facilitation, which are described, all the nervous dogs that showed an original “interest” for the qua.l were trained as successful hunted dogs, not obviously different in final performance from their normal kennel mates. Although the nervous dogs overcame their freezing, hyper-startle and human aversion while hunting, generalization did not extend sufficiently to normalize standard behavior test scores obtained under laboratory conditions. These remained at their prerehabilitation level, raising the question of the adequacy of the behavioi tests conducted in a laboratory environment. This appears to be related to the limitations often seen in psychotherapeutic efforts.     

Social anxiety and cognitive expectancy of aversive outcome in avoidance conditioning

Fear conditioning studies have shown that social anxiety is associated with enhanced expectancy of aversive outcome. However, the relation between cognitive expectancy and social anxiety has never been tested in avoidance conditioning paradigms. We compared 48 low (LSA) and high socially anxious individuals (HSA) on subjective expectancy of aversive outcome during an avoidance conditioning task. Displays of neutral faces were coupled with an aversive outcome (US): a shout and a shock. Participants could avoid the US by pressing a correct button from a button box. First, HSA showed higher US expectancy than LSA during the initial phase of avoidance conditioning, supporting the view that socially anxious individuals have an expectancy bias when social situations are ambiguous. Second, when the avoidance response became unavailable, LSA showed lower US expectancy than HSA, suggesting that low socially anxious individuals are prone to a positive bias when perceived threat is high. A lack of such positive bias in socially anxious individuals may lead to higher susceptibility to safety behavior interpretations. Together, these findings support the role of cognitive processes in avoidance conditioning and underscore the relevance to encounter avoidance learning when studying social anxiety.     

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.     

Lever attacking and pressing as a function of conditioning and extinguishing a lever-press avoidance response in rats

Six experimental rats were conditioned to press one of two available levers to avoid shock. The levers registered bites as well as presses. For four of these rats, shock was contingent on lever bites when a specified time period had elapsed after the previous shock. An extinction period, in which only periodic noncontingent shocks were presented, followed avoidance training. Six yoked-control rats received the same sequence of shocks as did the corresponding experimental rats in both the conditioning and extinction phases. All six experimental rats repeatedly bit the avoidance lever. Four bit it more than the nonavoidance lever during conditioning, and five bit it more during extinction. Five of the six experimental rats consistently bit the levers many more times during each session than did their respective control rats, suggesting that avoidance conditioning facilitated lever biting. Rates of lever biting and pressing by all of the experimental rats and by some of the control rats were highest immediately following shock throughout both phases. During later portions of the intervals following shock, characteristic effects of conditioning and extinction were observed. This finding suggests that extinction of avoidance behavior by unavoidable shock presentations can be demonstrated more readily when shock-elicited responding is extricated from the data.     

Bar holding during escape conditioning

To analyze bar-holding behavior during escape conditioning three rats were trained to escape from shock by pressing a bar, and three were trained to escape by releasing a bar. Bar holding behavior was stronger and more stable under the release condition. These effects were related to the relative shock duration of onbar versus offbar shocks.     

The operant and the classical in conditioned orientation of Drosophila melanogaster at the flight simulator

Ever since learning and memory have been studied experimentally, the relationship between operant and classical conditioning has been controversial. Operant conditioning is any form of conditioning that essentially depends on the animal's behavior. It relies on operant behavior. A motor output is called operant if it controls a sensory variable. The Drosophila flight simulator, in which the relevant behavior is a single motor variable (yaw torque), fully separates the operant and classical components of a complex conditioning task. In this paradigm a tethered fly learns, operantly or classically, to prefer and avoid certain flight orientations in relation to the surrounding panorama. Yaw torque is recorded and, in the operant mode, controls the panorama. Using a yoked control, we show that classical pattern learning necessitates more extensive training than operant pattern learning. We compare in detail the microstructure of yaw torque after classical and operant training but find no evidence for acquired behavioral traits after operant conditioning that might explain this difference. We therefore conclude that the operant behavior has a facilitating effect on the classical training. In addition, we show that an operantly learned stimulus is successfully transferred from the behavior of the training to a different behavior. This result unequivocally demonstrates that during operant conditioning classical associations can be formed.     

CER suppression, passive-avoidance learning, and stress-induced suppression of drinking in the Syracuse high- and low-avoidance strains of rats (Rattus norvegicus)

The Syracuse strains of Long-Evans rats were selectively bred for good (SHA) or poor (SLA) avoidance learning in a two-way shuttle box, which resulted in a phenotypic difference that is correlated with behavior patterns indicative of emotional reactivity, SLA animals showing evidence of greater emotional reactivity than SHA animals. The first three experiments examined conditioned suppression of bar pressing and compared paired and unpaired conditioned- and unconditioned-stimulus presentations to evaluate the influence of conditioning versus primary aversive stimulation on baseline responding. SLA animals acquired conditioned suppression faster than SHA animals and also showed greater suppression of baseline responding than SHA animals. In Experiment 4, SLA animals learned a passive-avoidance task faster than SHA animals. In Experiment 5, SLA animals showed greater stress-induced suppression of drinking a weak quinine solution than SHA animals. These data are consistent with the hypothesis that SLA animals are more emotionally reactive than SHA animals.     

A tracking procedure for determining the cat's frequency discrimination

A tracking procedure was used to investigate the time required to train cats to discriminate between a frequency-modulated tone and a steady tone. The animal was reinforced with food on a VR schedule only when the steady tone was present and the animal pressed the correct bar (one of two). After reinforcement, the steady tone usually changed to a frequency-modulated signal; by pressing the other bar, the tone could be changed to its steady state and the reinforcement then obtained as before. A major difficulty was the lack of control by the auditory stimulus on the cat's responses. This problem was solved by introducing interpress time outs which forced the animal to hesitate after every press. The use of light cues to signal the time outs and the correct bar to press accelerated the rate at which the training progressed.

With cats, this conditioning procedure apparently requires a much longer training period before the actual threshold determinations than the more commonly used avoidance conditioning procedures. However, when animals are to be tested repeatedly over a period of several months or longer, the procedure may prove the more desirable one because it reduces experimental neurosis.

     

Some new perspectives on conditioned hunger.

One theory holds that appetitive drives such as hunger and thirst are not conditionable because of their slow onset. However, recent evidence has shown only transitory conditioning of appetitive drives even with rapid onset. Such experiments may have failed because: (a) Exteroceptive conditioned stimuli (CSs) used in past experiments may be less easily accociated with the internal hunger drive than are interoceptive taste cues. Experiments 1-3 provided some support for this hypothesis. (b) The dependent measures used in past experiments may not be valid. Experiments 4 and 5 suggested that changes in the rate of bar pressing on an operant extinction curve following probe CSs for hunger may be a more sensitive and valid index of conditioned appetitive drive. However, the elusive and transitory nature of these results demands a reexamination of the basic difference between appetitive and aversive drives, which lies in the mode of their onset and control and which, given adaptive considerations, can account for their widely different conditionability.     

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.     

The effect of rearing environments on the contrafreeloading phenomenon in rats

Eight naive rats were reared in enriched or impoverished environments for 39 days after weaning and then lived in operant chambers, in which they could obtain food pellets freely or by lever pressing, for 25 or 30 days. The animals raised in an impoverished environment acquired the bar-press response quickly when placed in the operant chambers and maintained a preference for obtaining food via bar pressing. Animals raised in an enriched environment did not learn to lever press, as demonstrated by low levels of responding and the lack of bar pressing when free food was subsequently removed. It was concluded that restricting animals' postweaning environments facilitated learning in a choice situation, probably because of increased activity levels. The results are interpreted in relation to previous studies on rearing environments and on contrafreeloading.