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CSs and USs: What's the difference?
Abstract
Differences in processing representations of conditioned and unconditioned stimuli (CSs and USs) may result from either their temporal order in training (i.e., CSs precede USs) or the greater biological significance of USs. The CS- and US-preexposure effects were used to probe this question. These effects are similar except that context extinction between preexposure and training more readily attenuates the US- than the CS-preexposure effect. In Experiments 1, 2, and 5, context extinction following preexposure to the stimulus that later served as Event 1 in Event 1-->Event 2 pairings alleviated the response deficit due to Event 1 preexposure if Event 1 was biologically significant. In Experiments 3 and 4, context extinction alleviated the response deficit due to Event 2 preexposure if Event 2 was biologically significant. Thus, biological significance and not temporal order determines how a representation will be processed.
... Although enhanced subsequent responding is often seen, like cue-alone presentations, impaired subsequent responding is sometimes reported, and when it is, the effect is often explained in terms of degraded contingency. Thus, we see here [another] seeming symmetry between the processing of CSs and USs (Gunther et al., 1997). ...
Taking a test of previously studied material has been shown to improve long-term subsequent test performance in a large variety of well controlled experiments with both human and nonhuman subjects. This phenomenon is called the testing effect. The promise that this benefit has for the field of education has biased research efforts to focus on applied instances of the testing effect relative to efforts to provide detailed accounts of the effect. Moreover, the phenomenon and its theoretical implications have gone largely unacknowledged in the basic associative learning literature, which historically and currently focuses primarily on the role of information processing at the time of acquisition while ignoring the role of processing at the time of testing. Learning is still widely considered to be something that happens during initial training, prior to testing, and tests are viewed as merely assessments of learning. However, the additional processing that occurs during testing has been shown to be relevant for future performance. The present review offers an introduction to the historical development, application, and modern issues regarding the role of testing as a learning opportunity (i.e., the testing effect). We conclude that the testing effect is seen to be sufficiently robust across tasks and parameters to serve as a compelling challenge for theories of learning to address. Our hope is that this review will inspire new research, particularly with nonhuman subjects, aimed at identifying the basic underlying mechanisms which are engaged during retrieval processes and will fuel new thinking about the learning-performance distinction. (PsycInfo Database Record (c) 2022 APA, all rights reserved).
... However, the inherent relation of the CS and the US is not the only factor determining rate or vigor of learning. Biologically significant or more intense CSs and USs also lead to faster and more robust learning (Gunther et al., 1997), and a pre-existing relation between the CS and US is not a requirement for learning. ...
In this chapter, we first introduce classical conditioning from a historical perspective. We then characterize what is learned during classical conditioning, and do so while noting some practical and functional implications of classical conditioning. In the second part, we provide a succinct overview of phenomena such as cue competition and interference, which have received attention in the laboratory. We also describe major theoretical ideas that have been proposed to account for these phenomena. While there is a long was to go in achieving a better understanding of classical conditioning, research conducted in the last century has certainly paved the way for a better understanding of learning in humans and other animals.
... In addition, the pre sen ta tion of an unconditioned stimulus, US (e.g., food), is able to produce, additionally, an unconditioned response (UR) or physiological reflex (e.g., salivation by hungry dogs presented with food). In the conditioning procedure, one must pres ent a neutral stimulus immediately before the US (Gunther, Miller, and Matute, 1997). The repeated pairings of these two stimuli have the consequence of creating/strengthening an association between the mental repre sen ta tions of both of these cues. ...
In the last decades, cognitive Psychology has provided researchers with a powerful background and the rigor of experimental methods to better understand why so many people believe in pseudoscience, paranormal phenomena and superstitions. According to recent evidence, those irrational beliefs could be the unintended result of how the mind evolved to use heuristics and reach conclusions based on scarce and incomplete data. Thus, we present visual illusions as a parallel to the type of fast and frugal cognitive bias that underlies pseudoscientific belief. In particular, we focus on the causal illusion, which consists of people believing that there is a causal link between two events that coincide just by chance. The extant psychological theories that can account for this causal illusion are described, as well as the factors that are able to modulate the bias. We also discuss that causal illusions are adaptive under some circumstances, although they often lead to utterly wrong beliefs. Finally, we mention several debiasing strategies that have been proved effective in fighting the causal illusion and preventing some of its consequences, such as pseudoscientific belief.
... What is less clear, however, is whether outcomes that have been shown to be unpredictable in the past will be learnt about more slowly than previously predictable outcomes. Gunther, Miller and Matute (1997) noted the similarity in factors that affect 'CS pre-exposure' effects and 'US pre-exposure' effects. They highlighted the possibility that, just as cue associability has been shown to influence subsequent learning, so too might parallel 'outcome associability' influence learning. ...
... In this and previous work (e.g., Denniston, Miller, & Matute, 1996;Gunther, Miller, & Matute, 1997;Obcding et al., 1999), we have attempted to provide the beginnings of a principled account of biological significance by systematically exploring the various ways this variable interacts with other better known variables (e.g., associative value) to determine responding. Until now, biological significance has played a vague and inconsistent role in many theories of Pavlovian and instrumental learning (e.g., Hull, 1943;Pavlov, 1927;Thomdike, 1911). ...
In 3 Pavlovian conditioned lick-suppression experiments, rats received overshadowing treatment with a footshock unconditioned stimulus such that Conditioned Stimulus (CS) A overshadowed CS X. Subjects that subsequently received CS X paired with an established signal far saccharin (CS B) exhibited less overshadowing of the X-footshock association than subjects that did not receive the X-B pairings (Experiment I). Experiment 2 replicated this effect and controlled for some additional alternative accounts of the phenomenon. In Experiment 3, this recovery from overshadowing produced by counterconditioning CS X was attenuated if CS B was massively extinguished prior to counterconditioning. These results are more compatible with models of cue competition that emphasize differences in the expression of associations than those that emphasize differences in associative acquisition.
... A context-dependent reduction in responding during EBCC has been demonstrated in rabbits that showed a drop in conditioned responding of 50% when given pairings in a different context where the visual, tactile, and olfactory characteristics had been altered from the original training context (109). The reduction in responding as a result of a context shift during rabbit EBCC has been reported in other learning paradigms including fear conditioning (110,111), taste aversion learning (112), and conditioned suppression (113). Consistent with this context shift effect, our context experiments show that if exposure to the contexts is equated (111), CRM can be significantly reduced, but not eliminated, by a shift in the context from training to testing. ...
Not everyone exposed to trauma suffers flashbacks, bad dreams, numbing, fear, anxiety, sleeplessness, hyper-vigilance, hyperarousal, or an inability to cope, but those who do may suffer from post traumatic stress disorder (PTSD). PTSD is a major physical and mental health problem for military personnel and civilians exposed to trauma. There is still debate about the incidence and prevalence of PTSD especially among the military, but for those who are diagnosed, behavioral therapy and drug treatment strategies have proven to be less than effective. A number of these treatment strategies are based on rodent fear conditioning research and are capable of treating only some of the symptoms because the extinction of fear does not deal with the various forms of hyper-vigilance and hyperarousal experienced by people with PTSD. To help address this problem, we have developed a preclinical eyeblink classical conditioning model of PTSD in which conditioning and hyperarousal can both be extinguished. We review this model and discuss findings showing that unpaired stimulus presentations can be effective in reducing levels of conditioning and hyperarousal even when unconditioned stimulus intensity is reduced to the point where it is barely capable of eliciting a response. These procedures have direct implications for the treatment of PTSD and could be implemented in a virtual reality environment.
In recent years, several studies of human predictive learning demonstrated better learning about outcomes that have previously been experienced as consistently predictable compared to outcomes previously experienced as less predictable, namely the outcome predictability effect. As this effect may have wide-reaching implications for current theories of associative learning, the present study aimed to examine the generality of the effect with a human goal-tracking paradigm, employing three different designs to manipulate the predictability of outcomes in an initial training phase. In contrast to the previous studies, learning in a subsequent phase, when every outcome was equally predictable by novel cues, was not reliably affected by the outcomes’ predictability in the first phase. This lack of an outcome predictability effect provides insights into the parameters of the effect and its underlying mechanisms.
Much empirical work and theoretical discussion in the associative learning literature has focussed on when and how a cue changes in its associability. A series of new findings in human learning preparations (collectively referred to as the “outcome predictability” effect) appear to show that outcomes vary in their capacity to enter into novel associations as a product of their associative history. This effect is reminiscent of how cues change in associability as a consequence of their reinforcement history. We review the new findings within a broader associative literature that has previously investigated how conditioning can modify the effectiveness of outcome events to motivate new learning. A variety of explanations arising from this review are then critically considered. The article concludes by identifying novel questions brought into focus by the outcome predictability effect.
Two experiments with rats were conducted to analyse those mechanisms involved in non-nutritive flavor preference learning (e.g. Fedorchak, 1997). The first experiment involved a between-subject design intended to investigate the development of a conditioned taste preference to a non-preferred taste (citric acid). Specifically, water-deprived rats had access to a compound of citric acid and a non-caloric liked taste (saccharin) diluted in tap water (Capaldi, Hunter y Lyn, 1997). A preference for the citric acid was developed as compared to a group that experienced citric acid and saccharine uncorrelated. Experiment 2 was designed to evaluate the possible role of associative mechanisms on this kind of learning. Thus, after the conditioning of a preference to the citric acid by pairing it with saccharine, it was given a revaluation treatment by pairing the saccharine with an i.p. administration of LiCl. The results of this experiment revealed that the conditioned preference to the citric acid was reduced after the revaluation treatment. These results point to the relevance of associative mechanisms on taste-taste learning.
Review of the literature indicates that, according to theories of selective attention, learning about a stimulus depends on attending to that stimulus; this is represented in 2-stage models by saying that Ss switch in analyzers as well as learning stimulus-response associations. It is argued that this assumption, however, is equally well represented in a formal model by the incorporation of a stimulus-specific learning-rate parameter, a, into the equations describing changes in the associative strength of stimuli. Previous theories of selective attention have also assumed that (a) Ss learn to attend to and ignore relevant and irrelevant stimuli (i.e., that a may increase or decrease depending on the correlation of a stimulus with reinforcement); and (b) there is an inverse relationship between the probabilities of attending to different stimuli (i.e., that an increase in a to one stimulus is accompanied by a decrease in a to others). The first assumption has been used to explain the phenomena of acquired distinctiveness and dimensional transfer, the second to explain those of overshadowing and blocking. It is argued that although the first assumption is justified by the data, the second is not: Overshadowing and blocking are better explained by the choice of an appropriate rule for changing a, such that a decreases to stimuli that signal no change from the probability of reinforcement predicted by other stimuli. (65 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
The effect of a retention interval on latent inhibition was studied in three experiments by using rats and the conditioned
taste-aversion procedure. In Experiment 1, we demonstrated an apparent loss of latent inhibition (i.e., a strengthening of
the aversion) in preexposed subjects that experienced a retention interval of 12 days between conditioning and the test. In
Experiment 2, we found no effect of this retention interval on the habituation of neophobia produced by the phase of exposure
to the flavor. In Experiment 3, we showed that interposing a retention interval between preexposure and conditioning produced
effects exactly comparable to those seen in Experiment 1. The implications of these results for rival theories of latent inhibition,
as an acquisition deficit or as a case of interference at retrieval, are discussed.
Conditioned lick suppression in rats was used to explore the role of timing in trace conditioning. In Experiment 1, two groups
of rats were exposed to pairings of a CS (CS1) with a US, under conditions in which the interstimulus interval (ISI) that
separated CS1 offset and US onset was either 0 or 5 sec. Two additional groups were also exposed to the same CS1→US pairings
with either a 0 or a 5-sec ISI, and then received “backward” second-order conditioning in which CS1 was immediately followed
by a novel CS2 (i.e., CS1→CS2). A trace conditioning deficit was observed in that the CS1 conditioned with the 5-sec gap supported
less excitatory responding than the CS1 conditioned with the 0-sec gap. However, CS2 elicited more conditioned responding
in the group trained with the 5-sec CS1-US gap than in the group trained with the 0-sec CS1-US gap. Thus, the CS1-US interval
had inverse effects on first- and second-order conditioned responding. Experiment 2 was conducted as a sensory preconditioning
analogue to Experiment 1. In Experiment 2, rats received the CS1?CS2 pairings prior to the CS1→US pairings (in which CS1 was
again conditioned with either a 0 or a 5-sec ISI). Experiment 2 showed a dissociation between first- and second-order conditioned
responding similar to that observed in Experiment 1. These outcomes are not compatible with the view that differences in responding
to CSs conditioned with different ISIs are mediated exclusively by differences in associative value. The results are discussed
in the framework of the temporal coding hypothesis, according to which temporal relationships between events are encoded in
elementary associations.
Treatments that attenuate latent inhibition (LI) were examined using conditioned suppression in rats. In Experiment 1, retarded
conditioned responding was produced by nonreinforced exposure to the CS prior to the CS-US pairings used to assess retardation
(i.e., conventional LI). In Experiment la, retarded conditioned responding was induced by preexposure to pairings of the CS
and a weak US prior to retardation-test pairings of the CS with a strong US (i.e., Hall-Pearce [1979] LI). Both types of LI
were attenuated by extensive exposure to the training context (i.e., context extinction) following the CS-US pairings of the
retardation test. Experiment 2 examined the specificity of the attenuated LI effect observed in Experiment 1. After preexposure
to two different CSs in two different contexts, each CS was paired with a US in its respective preexposure context. One of
the two contexts was then extinguished. This attenuated LI to a greater degree for the CS that had been trained in the extinguished
context. Experiment 3 differentiated the roles in LI of CS-context associations and context-US associations. Following preexposure
to the CS in the training context, LI was reduced by further exposure to the CS outside the training context. This observation
was interpreted as implicating the CS-context association as a factor in LI. Thus, the results of these experiments suggest
that LI is a performance deficit mediated by unusually strong CS-context associations. Implications for Wagner’s (1981) SOP
model and Miller and Matzel’s (1988) comparator hypothesis are discussed.
A conditioned emotional response procedure was used to study the interactive effects of stimulus preexposure and retention
interval in rats. In Experiment 1, the subjects were conditioned by presenting a light CS paired with mild footshock as the
US. Half of the subjects were given nonreinforced preexposure to the CS, and the others were not. Separate preexposed and
nonpreexposed groups were then tested 1,7, or 21 days after conditioning. Suppression of ongoing activity was used to assess
the degree of conditioned fear. Latent inhibition was found at the 1-day retention interval; the preexposed subjects displayed
less conditioned fear than did the nonpreexposed subjects. In contrast, equally strong conditioned fear was expressed by the
preexposed and the nonpreexposed groups tested after the 7- and the 21-day retention intervals. These results indicate a release
from latent inhibition similar to that obtained with conditioned taste aversions (Kraemer & Roberts, 1984). The results of
Experiment 2 suggest that retention-interval-induced increases in sensitization, pseudoconditioning, or neophobia cannot account
for the release from latent inhibition effect obtained in Experiment 1. The implications of these findings for a retrievaloriented
view of latent inhibition are discussed.
This chapter describes the potential explanatory power of a specific response rule and its implications for models of acquisition. This response rule is called the “comparator hypothesis.” It was originally inspired by Rescorla's contingency theory. Rescorla noted that if the number and frequency of conditioned stimulus–unconditioned stimulus (CS–US) pairings are held constant, unsignaled presentations of the US during training attenuate conditioned responding. This observation complemented the long recognized fact that the delivery of nonreinforced presentations of the CS during training also attenuates conditioned responding. The symmetry of the two findings prompted Rescorla to propose that during training, subjects inferred both the probability of the US in the presence of the CS and the probability of the US in the absence of the CS and they then established a CS–US association based upon a comparison of these quantities. The comparator hypothesis is a qualitative response rule, which, in principle, can complement any model of acquisition.
Many researchers have noted the similarities between causal judgment in humans and Pavlovian conditioning in animals. One recently noted discrepancy between these two forms of learning is the absence of backward blocking in animals, in contrast with its occurrence in human causality judgment. Here we report two experiments that investigated the role of biological significance in backward blocking as a potential explanation of this discrepancy. With rats as subjects, we used sensory preconditioning and second-order conditioning procedures, which allowed the to-be-blocked cue to retain low biological significance during training for some animals, but not for others. Backward blocking was observed only when the tar get cue was of low biological significance during training. These results suggest that the apparent discrepancy between human causal judgment and animal Pavlovian conditioning arises not because of a species difference, but because human causality studies ordinarily use stimuli of low biological significance, whereas animal Pavlovian studies ordinarily use stimuli of high biological significance, which are apparently protected against cue competition.
The hypothesis that latent inhibition could be reduced by extinguishing the experimental context, that is, exposing the rats to the context between exposure to the conditional stimulus (CS) and conditioning, was tested. All experiments used the conditioned emotional response procedure. In Experiment 1, extinction was not effective when the animals were exposed to the clicker 40 times off the baseline of responding for food and when the clicker CS was partially reinforced with shocks during the test phase. In Experiments 2 and 3, latent inhibition could be reduced by extinction if the animals were exposed to the CS 24 or 16 times on-baseline, and if continuous reinforcement was used during the test. In Ex- periments 4, 5, and 6, we attempted to determine which variable was responsible for the discrepant results. In Experiment 4, extinction was effective with 20 or 40 on-baseline exposures to the CS, using continuous reinforcement during the test. In Experiment 5, extinction was not effective with exposure on- or off- baseline, using 24 exposures and partial reinforcement. Finally, in Experiment 6, extinction reduced latent inhibition using continuous, but not partial, rein- forcement with 40 exposures off-baseline. From these results, we concluded that Wagner's model of habituation was not sufficient to account for latent inhibition and that a hybrid model, using both associative and cognitive representational processes, was necessary.
Conducted 3 experiments using a conditioned suppression procedure in male Sprague-Dawley rats. Exp I and II (N = 56) found that exposure to a more severe shock either before or after conditioning elevated the CR established by a moderate shock. Exp III (n = 32) found 2nd-order conditioning immune to such modification. These findings parallel earlier results with habituation of the UCS in the absence of the CS. They encourage the view that organisms form memories of the UCS independently of associative connections with the CS. (PsycINFO Database Record (c) 2012 APA, all rights reserved)