Frank A. Logan

Aggressive Behaviors of Paired Rodents in an Avoidance Context

Although the number of rodents of different species and sexes was somewhat small, the consistency of the results enables a reasonably confident description of the effect of pairing rodents in an avoidance context. Considering first the situation in which both rodents were required to make the same manipulatory response to avoid or escape from electric shock: I. Naive rodents paired in this situation do not learn to avoid the shock by responding after the onset of a warning signal and before the shock. In the same situation, the rodents avoid 75-90 percent of the shocks if trained singly. This deficit is not the result of failing to notice the warning signal nor detecting its significance; the incidence of crouching, squealing and anticipatory foot-stomping indicate that the warning signal had acquired secondary aversive properties. 2. The presence of two rodents in the same avoidance situation does not materially affect their escape behavior when viewed at the molar level of the latency of escape responses. At a more molecular level, however, the escape response was almost invariably executed by the rat judged to be submissive when paired outside the avoidance context. When the shock was not quickly terminated, the dominant rat made distinct threat and aggressive responses such as foot-stomping and aborted attack until the submissive rat turned the wheel. 3. After the termination of the shock, the rodents engaged in various forms of interaction of an aggressive nature, including sparring, muzzling, over-and-under, and actual fighting. The most dramatic form observed was mounting with pelvic thrusting by the dominant rodent, even if it was a sexually naive female in the presence of another non-receptive female. 4. Essentially the same pattern of behavior was observed if either or both of the rodents had been pretrained singly in the apparatus either to escape or to avoid the shock. In the case of laboratory rats, which were observed to remain in close proximity to each other, the disappearance of avoidance behavior was more gradual than in their wild counterparts. In the case of the Florida packrats, which were observed to remain very far apart in the apparatus, avoidance behavior gradually reappeared. 5. The pairing of rodents in an avoidance situation had a dramatic effect upon their subsequent behavior when introduced into the situation singly. Even if they had previously learned the avoidance response individually, very little avoidance behavior was observed after a few sessions paired with another rodent. 6. All of the above observations are specific to the situation in which the same manipulatory response is required of both rodents. If a shuttle avoidance situation is employed,in which the necessity for confrontation in making the response is obviated, then avoidance behavior by both rodents continues when paired essentially at the same level as when run singly.

Incentive Theory and Changes in Reward1

Publisher Summary This chapter focuses on incentive theory and changes in reward. Changes in incentive motivation are essential aspects of contemporary theories of learning, but little attention has been paid to the rate at which such changes take place. If the incentive motivation is mediated by a response mechanism, then the laws of classical conditioning would suffice to describe incentive change effects. Incentive motivation is only one of the conceptual determinants of instrumental performance, and hence cannot be measured directly. Nevertheless, it is assumed that choice between two alternatives that are otherwise equivalent can be used to index their relative incentive values. The rate at which incentive motivation changes in response to a change in the reward conditions was evaluated empirically in the chapter by using a choice procedure with rats as subjects. The assumption of invariant rates of change in incentive motivation is a tenable one. When the incentive value of the reward received after a response differs from the preexisting incentive motivation for that response, an appropriate change occurs at a rate that is more or less independent of prior experimental history.

Animal Learning and Motivation and Addictive Drugs

Highlights of a systematic analysis of the abstracts of over 1700 publications dealing with addictive drugs (primarily alcohol) in the context of animal learning and motivation are summarized under two main headings. The behavioral effects of drugs vary with the nature of the drug, the dosage, and the behavioral baseline; behavioral tolerance frequently results from continued practice in the drug state. The paradigmatic effects show that drugs can function effectively as conditional stimuli, unconditional stimuli, responses, and reinforcers. As a result, drug habits develop their own motivational support, leading to conditioned tolerance and conditioned addiction. It is contended that principles of animal behavior can provide a basis for a theory of human drug use and abuse, but that voluntary control of addictive behavior requires uniquely human cognitive processes.

Avoidance of a warning signal

Rats were scheduled to receive electric shock every 20 sec, half under the typical nondiscriminated procedure where shock is scheduled from the last response, and half under a fixed-cycle procedure where shock is scheduled regularly by time. For half of each of these groups, a 4 sec CS preceded the shock. In the latter procedure, most avoidance responses occurred before (and hence also avoided) the CS. The difference was attributed to the relative efficiency of avoiding a warning signal.

Sexual free behavior in male rats (Rattus norvegicus).

Male rats (Rattus norvegicus) were given continuous access to estrous female rats for 24 hr each day for 10 days. During the first 12 hr, the rats achieved an average of 10 ejaculations, followed by a 1- to 2-day recovery period with little sexual activity. During the last 7 days, the rats maintained a reasonably stable equilibrium level of 3 ejaculations per day. These occurred predominantly during the dark phase of the diurnal cycle, they frequently occurred in a cluster, and they usually occurred shortly after the introduction of a novel estrous female. Except for quantitative differences, these results are generally consistent with conventional research but systematically extend the generality of the results to the context of the free behavior situation. The availability of sexual activity had no appreciable effect on food and water intake, but it did decrease the amount of running activity.

Item similarity and proactive interference in short-term memory

The present paper addresses the question of the nature of interitem similarity effects in short-term retention. An interference theory prediction is pitted against an opposing expectation based on a cognitive strategy subjects could use in the “release-from-PI” paradigm. The experiment consisted of three conditions that differed in the extent of overlap among items in the short-term retention task. Results supported interference theory, in that increasing the interitem similarity of the to-be-recalled items resulted in a substantial decrease in correct recall.

Differential trace conditioning to temporal compounds

Rats were reinforced for responding following the presentation of a light-tone temporal compound, each component having a .5-sec duration separated by a .5-sec empty interval. For different groups, nonreinforced presentations of the compound in the reverse order and either or both of the components separately were included in each session. Results indicated a progressive increase in difficulty as the number of nonreinforced events increased, with behavior being strongly affected by the first component of the compound. Nevertheless, differential performance under the most demanding conditions demonstrate the rat’s ability to acquire a temporal compound discrimination, which suggests an interpretation based on interacting stimulus traces.

HYBRID THEORY: WHAT IS LEARNED IN CLASSICAL CONDITIONING?

Experimental evidence can be interpreted to imply an S-S associative process in classical (Pavlovian) conditioning and an S-R associative process in higher-order conditioning. The evidence comes from the differential effects of changing the value/significance of the US after conditioning. However, all results can be attributed to S-S associations if anticipatory response-produced feedback is included in the analysis. This analysis also has implications for the relation of the CR to the UR and equipotentiality of associability.

Preference for punishment of the instrumental or the consummatory response

In two discriminable runways, rats were punished (shocked) either prior to receiving water reinforcement (punishment of the instrumental response) or after ingesting the water (punishment of the consummatory response). Both forced-choice and free-choice trials were conducted. Results indicate that rats preferred to have the instrumental response punished. It was also observed that the subjects more frequently failed to traverse the runway in which the consummatory response was punished compared to the runway in which the instrumental response was punished. The results were interpreted as being consistent with predictions derived from net incentive theory.

Operant behavior in transition: FI to FI

Three rats received extensive initial training on an FI 2-min schedule of reinforcement and were then shifted to an FI 30-sec schedule. The length of the postreinforcement pause very rapidly decreased, suggesting that the rats were “surprised” by the changed schedule. The subsequent shift back to the FI 2-min schedule led to a gradual change in performance, with responding appropriate to both intervals occurring.