Conditions for establishing stimuli which inhibit conditioned fear reactions are demonstrated in 3 experiments. Dogs, trained in a shuttle box to avoid shock on a Sidman avoidance schedule, received Pavlovian fear conditioning involving the presentation of tones and shock in various temporal relations. Subsequently, these tones were presented while S performed the avoidance response. Stimuli preceding shock in conditioning increased rate of avoidance; Pavlovian conditioned and discriminative inhibitors depressed it. Furthermore, a stimulus whose presentation was "contrasted" with that of shock depressed the avoidance rate. These findings imply that inhibitory as well as excitatory Pavlovian processes are involved in fear conditioning. Implications for pseudoconditioning control procedures and reinforcement of avoidance behavior are discussed.
Excitatory Pavlovian conditioning of a discrete conditioned stimulus is attenuated by prior exposure to the unconditioned stimulus. The unconditioned stimulus preexposure phenomenon is observed in a variety of Pavlovian conditioning procedures as diverse as eyelid conditioning, the conditioned emotional response, and conditioned taste aversion learning. This article discusses the variables that affect the unconditioned stimulus preexposure phenomenon and uses this information in evaluating both associative and nonassociative accounts of the phenomenon. At least one associative account, based on context blocking, and at least one nonassociative account, based on central habituation of the emotional response to the unconditioned stimulus, remain viable.
Groups of pigeons were trained to depress a treadle in the presence of a compound stimulus consisting of a tone and a red house light (a) to avoid electric shock or (b) to obtain grain. Responding in the absence of the compound stimulus postponed its next occurrence. After performance had stabilized, the degree to which the compound and each element controlled treadle pressing was determined. In the appetitive test, many responses were made in the presence of the compound and the light alone, but very few were made to the tone alone. In the avoidance test, very few responses occurred in the presence of the light alone, an intermediate number to the tone alone, and most in the presence of the compound.
Effects of Pavlovian conditioning procedures in which CS follows US were demonstrated in dogs. In Experiment 1, tone onset occurred 1 sec. before (cessation-conditioning group) or 1 sec. after (backward-conditioning group) shock termination; presentation of CSs during Sidman avoidance responding in the shuttle box resulted in decreased rates. In Experiment 2, tone following shock termination by 15 sec. produced similar effects, while CS which followed shock termination by 1 sec., but was not reliably followed by a long ITI, was ineffective. Thus, although these procedures produce inhibition of fear, this result is not due to a backward associational process, but to the fact that, when CS follows US and the ITI is long, the CS signals safety.
In the present experiments, the outcome specificityof learning was explored in an appetitive Pavlovian backward conditioning procedure with rats. The rats initially were administered Pavlovian backward training with two qualitatively different unconditioned stimulus conditioned-stimulus (US-CS) pairs of stimuli (e.g., pellet ® noise or sucrose ® light), and then the effects of this training were assessed in Pavlovian-to-instrumental transfer (Experiment 1) and retardation-of-learning (Experiment 2) tests. In the transfer test, it was shown that during the last 10-sec interval, the CSs selectively reduced the rate of the instrumental responses with which they shared a US, relative to the instrumental responses with which they did not share a US. The opposite result was obtained when the USs (in the absence of the CSs) were presented noncontingently. In the retardation test, conditioned magazine approach, responding to the CSs was acquired more slowly when the stimulus-outcome combinations in the backward and the forward conditioning phases were the same, as compared with when they were reversed. These results are collectively in accord with the view that Pavlovian backward conditioning can result in the formation of outcome-specific inhibitory associations. Alternative views of backward conditioning are also examined.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.