Latent inhibition experiments with goldfish (Carassius auratus)

Evidence of latent inhibition was sought in a series of experiments with goldfish. In Experiment 1, goldfish were given nonreinforced preexposure to a color that subsequently predicted shock in an activity conditioning situation; their performance did not differ from that of control animals preexposed to a markedly different color. In Experiment 2, a group of goldfish given nonreinforced preexposure to a tone and an unstimulated control group were trained in an appetitive situation, with the tone serving either as a conditioned excitor or as a conditioned inhibitor. Preexposure had no significant effect in the conditioned excitation training, but it reduced the level of responding both to the positive stimulus and to the negative compound in the conditioned inhibition training. In Experiments 3 and 4, classical aversive conditioning was studied in the shuttle box. In Experiment 3, excitatory conditioning to a color was found to be impaired (relative to the performance of nonpreexposed control animals) as much by nonreinforced preexposure to the training color as by nonreinforced preexposure to a markedly different color; substantial variation in amount of preexposure was without significant effect. In the conditioned inhibition training of Experiment 4, animals with nonreinforced preexposure responded less than did unstimulated control animals both to the positive stimulus and to the negative compound. The results for goldfish can be understood on the assumption that the effect of preexposure in these animals is simply to reduce general responsiveness or level of arousal.     

A comparator view of Pavlovian and differential inhibition

In 3 experiments using rats as subjects, the authors varied trial spacing to investigate the conditions under which Pavlovian and differential inhibition are observed. Experiment 1 compared Pavlovian and differential inhibition with spaced training trials. Spaced trials resulted in only the Pavlovian inhibitor passing both summation and retardation tests. Conversely, Experiment 2 compared these 2 types of inhibition with massed training trials. This training resulted in only the differential inhibitor passing both tests for conditioned inhibition. Finally, in Experiment 3 all subjects experienced Pavlovian inhibition training with massed trials. Although this training by itself did not result in behavior indicative of inhibition, subjects that also experienced posttraining extinction of the training context did pass both tests for inhibition. Overall, these results are anticipated by the extended comparator hypothesis (Denniston, Savastano, & Miller, 2001) but are problematic for most contemporary associative learning theories.     

Conditioned Inhibition in a Multiple Category Learning Task

Four experiments investigated inhibition that might arise in a task in which cues are associated with more than one outcome. In each experiment, human subjects played a game called 'Clues and Culprits' in which they were asked to judge the predictive strength of clues that had been associated with culprits in a series of hypothetical crimes. In a two-outcome version of the familiar conditioned inhibition paradigm (A+, AX- ), one clue was paired with one culprit on its own, but it was paired with a second culprit when it was combined with a second clue (A-1, AX-2). According to the delta rule, X should acquire inhibition for the first culprit; it should also acquire more inhibition than a differential cue merely associated with a second culprit (e.g. A-1, X-2). Inhibition was found with both procedures. However, the amount of inhibition did not differ between them, suggesting that mere association with a second outcome was sufficient to inhibit performance based on the first. Other data suggested the presence of cue competition. Also, when a cue associated with one culprit was paired with a second culprit on other trials, there was little evidence of unlearning of the first association.     

The hide-and-seek of retrospective revaluation: recovery from blocking is context dependent in human causal learning

In a typical blocking procedure, pairings of a compound consisting of 2 stimuli, A and X, with the outcome are preceded by pairings of only A with the outcome (i.e., A+ then AX+). This procedure is known to diminish responding to the target cue (X) relative to a control group that does not receive the preceding training with blocking cue A. We report 2 experiments that investigated the effect of extinguishing a blocking cue on responding to the target cue in a human causal learning paradigm (i.e., A+ and AX+ training followed by A- training). The results indicate that extinguishing a blocking cue increases conditioned responding to the target cue. Moreover, this increase appears to be context dependent, such that increased responding to the target is limited to the context in which extinction of the blocking cue took place. We discuss these findings in the light of associative and propositional learning theories.     

Enhancement of Pavlovian conditioned inhibition achieved by posttraining inflation of the training excitor

In two conditioned lick suppression experiments using water-deprived rats, we examined the effects of following Pavlovian conditioned inhibition training (i.e., A–US/AX-NoUS) with pairings of the training excitor (A) and the unconditioned stimulus (US). Experiments 1 and 2 assessed the effects of this posttraining inflation treatment on Pavlovian conditioned inhibition using a summation test and a retardation test, respectively. Both experiments revealed that subjects exposed to inflation treatment demonstrated behavior indicative of enhanced conditioned inhibition compared to subjects that did not receive inflation treatment. The results in conjunction with other recent findings suggest that posttraining associative deflation (i.e., extinction of A) and inflation effects are more symmetrical than has previously been realized.     

Conditioned inhibition produced by extinction-mediated recovery from the relative stimulus validity effect: a test of acquisition and performance models of empirical retrospective revaluation

Empirical retrospective revaluation is a phenomenon of Pavlovian conditioning and human causal judgment in which posttraining changes in the conditioned response (Pavlovian task) or causal rating (causal judgment task) of a cue occurs in the absence of further training with that cue. Two experiments tested the contrasting predictions made by 2 families of models concerning retrospective revaluation effects. In a conditioned lick-suppression task, rats were given relative stimulus validity training, consisting of reinforcing a compound of conditioned stimuli (CSs) A and X and nonreinforcement of a compound of CSs B and X, which resulted in low conditioned responding to CS X. Massive posttraining extinction of CS A not only enhanced excitatory responding to CS X, but caused CS B to pass both summation (Experiment 1) and retardation (Experiment 2) tests for conditioned inhibition. The inhibitory status of CS B is predicted by the performance-focused extended comparator hypothesis (J. C. Denniston, H. I. Savastano, & R. R. Miller, 2001), but not by acquisition-focused models of empirical retrospective revaluation (e.g., A. Dickinson & J. Burke, 1996; L. J. Van Hamme & E. A. Wasserman, 1994).     

Contrasting reduced overshadowing and blocking

Preexposure of a cue without an outcome (X-) prior to compound pairings with the outcome (XZ-->O) can reduce overshadowing of a target cue (Z). Moreover, pairing a cue with an outcome (X-->O) before compound training can enhance its ability to compete with another cue (i.e., blocking). Four experiments were conducted in a conditioned bar-press suppression preparation with rats to determine whether spacing of the X- or X-->O trials would differentially affect reduced overshadowing and blocking. Experiment 1a showed that reduced overshadowing was larger with massed trials than with spaced trials. Experiment 1b found that blocking was larger with spaced trials than with massed trials. Experiments 2a and 2b indicated that these effects of trial spacing were both mediated by the associative status of the context at test. The results are interpreted in the framework of contemporary learning theories.     

Cue interaction in human contingency judgment

Most studies of human contingency judgment have been based on the assumption that frequency information about one predictor is assessed in isolation of information about other predictors. Recent evidence, however, suggests that the judged predictive strength of one cue is influenced by the predictive strengths of other copresent cues. Two experiments demonstrate that stimuli with the same outcome contingencies may nonetheless have different predictive strengths as the result of cue interaction. The first experiment, in which a within-subject design was used, provides a demonstration of blocking. A stimulus presented in compound with a strong predictor was rated as less predictive than another stimulus that was presented in compound with a nonpredictive cue. In the second experiment, cue interactions in conditioned inhibition were examined. A stimulus gained negative predictive strength as the result of compound presentations with a positive predictor when the outcome was not presented. This negative predictor was compared with an otherwise analogous stimulus that was not presented in compound with a positive predictor. These results support the use of animal-conditioning models as accounts of human contingency learning.     

Transfer of negative occasion setting and conditioned inhibition across conditioned and unconditioned stimuli

The transfer of negative occasion setting and conditioned inhibition across conditioned stimuli (CSs) and unconditioned stimuli (USs) was examined in four experiments that used Pavlovian appetitive feature negative discrimination training procedures with rats. After training with simultaneous compounds (A+, XA-), X inhibited conditioned responding (CRs) elicited by other CSs and CRs supported by other appetitive USs that had not been involved in discrimination training. After training with serial compounds (A+, X----A-), X's power to set the occasion for nonresponding transferred across CSs and USs only if those events had also been involved in serial feature negative discrimination training. The results supported the suggestion that the acquisition of negative occasion setting involves the representation of individual events in a higher order memory system, separate from that involved in simple association, and that negative occasion setters act only on events that are represented in that system.     

Context-outcome associations mediate context-switch effects in a human predictive learning task

Four experiments explored the role of contexts in information retrieval after different levels of acquisition training in human predictive learning. Participants were trained where cue (X) was followed by an outcome in context A while a different cue (Y) was followed by the absence of the outcome in context B. When 4 training trials with each cue were conducted, testing the stimuli in the alternative contexts decreased predictive judgments to X and increased predictive judgments to Y. These effects disappeared both when training was increased up to 18 trials (Experiments 1a and 1b), and when the outcome was presented in both contexts A and B (Experiments 2 and 4). When the outcome was presented in both contexts, the nonreinforced cue Y, trained in the presumably excitatory context B, became a conditioned inhibitor (Experiment 3). Additional experience with one of the contexts, but not with both, made the context-switch effect reappear (Experiment 4). These results suggest that irrelevant contexts may enter into direct associations with the outcome before prolonged training leads participants to discard them as predictors.     

Trial spacing is a determinant of cue interaction

Four conditioned lick suppression experiments with rats examined the effect of trial spacing on cue interaction. Experiments 1 and 2 found overshadowing to be eliminated with massed compound stimulus-outcome pairings and the usual trial spacing effect to be reversed with compound acquisition trials. Experiment 3 found that whether acquisition compound-outcome pairings were massed or spaced determined the effect of posttraining extinction treatment. Extinction of the overshadowing cue reduced responding following massed training and increased responding following spaced training. Extinction of the context decreased responding following massed training. Experiment 4 found the conditioning and devaluation results to be associative and stimulus specific. These results are in accord with the extended comparator hypothesis (J. C. Denniston, H. I. Savastano, & R. R. Miller, 2001).     

The effect of an extinction cue on ABA-renewal: Does valence matter?

The present human fear conditioning study examined whether the valence of an extinction cue has a differential effect on attenuating renewal that is induced by removal of the extinction context. Additionally, the study aimed to assess whether such attenuating effect is based on a modulatory or safety-signal role of the cue. In acquisition, extinction, and test stages of the experiment, human participants received pairings of human faces, presented against a particular background color, with the presence or absence of an aversive auditory stimulus. Experimental groups differed in the valence of a cue that was presented during extinction, in whether or not extinction took place against a different background color than present during acquisition and testing, and in whether the extinction cue was present or absent at test. The conditioned response consisted of auditory-stimulus expectancy ratings. It was hypothesized that a positively valued extinction cue yields faster extinction, stronger attenuation of renewal, and better transfer of its inhibitory power to non-extinguished stimuli than a negatively valued cue. All three hypotheses were confirmed, suggesting that the positive, but not the negative, cue had become a safety signal. The results were discussed in the framework of extinction-based exposure treatments.     

Temporal coding in conditioned inhibition: analysis of associative structure of inhibition

Two experiments with rats as subjects were conducted to investigate the associative structure of temporal control of conditioned inhibition through posttraining manipulation of the training excitor-unconditioned stimulus (US) temporal relationship. Experiment 1 found that following simultaneous Pavlovian inhibition training (i.e., A --> US/XA-no US) in which a conditioned stimulus (CS A) was established as a delay excitor, maximal inhibition was observed on a summation test when CS X was compounded with a delay transfer CS. Furthermore, posttraining shifts in the A-US temporal relationship from delay to trace resulted in maximal inhibition of a trace transfer CS. Experiment 2 found complementary results to Experiment 1 with an A-US posttraining shift from serial to simultaneous. These results suggest that temporal control of inhibition is mediated by the training excitor-US temporal relationship.     

Super-learning of Causal Judgements

In three experiments, participants learned which of a variety of foods were capable of causing an allergic reaction in a hypothetical patient during training in which a compound of a treatment and a target food cue was paired with the reaction. In Experiment 1 the causal ratings of the target cue were increased if the treatment cue was pretrained as a preventative cause of the reaction. Experiments 2 and 3 demonstrated that the magnitude of this superlearning is unaffected by the order of compound and treatment cue training. The final study also showed that forward super-learning is not induced solely by simple exposure to the treatment cue prior to compound training but, rather, depends upon training the treatment cue as a preventative cause, whereas retrospective super-learning may be due merely to exposure of the treatment cue. These results are problematic for contingency-based accounts of causal induction but accord with modified and extended associative theories.     

Is the context specificity of latent inhibition a sufficient explanation of learned irrelevance?

In three experiments, rats were pre-exposed either to uncorrelated presentations of a light and sucrose pellets (group CS/US) or to equivalent presentations of the light and pellets in separate sessions (control). In Experiment 1, subsequent conditioning to the light proceeded more slowly in group CS/US than in the control group, whether this conditioning was excitatory, with the light signalling the delivery of pellets, or inhibitory, with the light signalling their absence. Bonardi and Hall (1996) have argued that this learned irrelevance effect may be reducible to latent inhibition, which would be stronger in group CS/US because they are both pre-exposed and conditioned to the CS in the presence of traces of previous USs occurring in the same session. This analysis implies that group CS/US should have conditioned more rapidly to the CS than controls on the first trial of each session in Experiment 1, but this did not happen. It also implies that the learned irrelevance effect should be reversed if conditioning trials are given at a rate of one per day . Experiments 2 and 3 found no support for this prediction. We conclude that learned irrelevance effects cannot always be reduced to latent inhibition.     

Recovery from blocking between outcomes

Contemporary associative learning research largely focuses on cue competition phenomena that occur when 2 cues are paired with a common outcome. Little research has been conducted to investigate similar phenomena occurring when a single cue is trained with 2 outcomes. Three conditioned lick suppression experiments with rats assessed whether treatments known to alleviate blocking between cues would also attenuate blocking between outcomes. In Experiment 1, conditioned responding recovered from blocking between outcomes when a long retention interval was interposed between training and testing. Experiment 2 obtained recovery from blocking between outcomes when the blocking outcome was extinguished after the blocking treatment. In Experiment 3, a recovery from blocking between outcomes occurred when a reminder stimulus was presented in a novel context prior to testing. Collectively, these studies demonstrate that blocking of outcomes, like blocking of cues, appears to be caused by a deficit in the expression of an acquired association.     

Extinction in human learning and memory

In two experiments, participants were given extinction training in a human causal learning task. In both experiments, three critical experimental cues were paired with different outcomes in a first phase of training and were then extinguished in a second phase. Three control cues were given the same treatment in the first phase of training, but were not then presented in the second phase. Participants' ability to correctly identify the outcome with which each cue had been paired in the first phase was lower for extinguished than for control cues. Causal attributions to the extinguished cues were also lower than those to the control cues, a difference that correlated with outcome memory. These data are consistent with the idea that extinction in causal judgement is due, at least in part, to a failure to remember the cue–outcome relationship encoded in the first phase of training.     

Dissociable effects of fear and disgust in proactive and reactive inhibition

Numerous studies have demonstrated that negative emotional distracters impair inhibitory control. Nevertheless, two issues have emerged in prior studies. First, fear and disgust were inappropriately treated as a single category, which is particularly concerning given that they have been recently demonstrated to exert different impacts on inhibitory control. Second, inhibitory control might not be a unitary construct, as it can be further divided into proactive and reactive inhibition. Therefore, the present study aimed to investigate whether fearful and disgusting distracters have differential effects on proactive and reactive inhibition. Twenty-four female participants were instructed to perform a modified stop-signal task superimposed on a fearful, disgusting, or neutral image cue. Results showed that fearful distracters improved reactive inhibition when compared to disgusting and neutral distracters, while disgusting distracters enhanced proactive inhibition when compared to fearful distracters. Further, reactive and proactive inhibition was positively correlated under fearful, disgusting, and neutral contexts. This study is the first to provide evidence that fear and disgust may affect proactive and reactive inhibition differently. These results add to a growing literature linking emotion and inhibitory control, and they expand our understanding of the relationship between emotion and inhibition.     

Backward conditioning: mediation by the context

The information acquired in backward conditioning (i.e., outcome-->cue) was assessed in 3 Pavlovian lick-suppression experiments with water-deprived rats as subjects. Experiment 1 confirmed previous research that few outcome-->cue pairings made the cue into a conditioned excitor and additionally showed that massive posttraining extinction of the training context attenuated a backward-trained cue's excitatory value. Experiment 2 found that many outcome-->cue pairings made the cue into a conditioned inhibitor and that the same context manipulation attenuated this inhibitory value. Experiment 3 confirmed the observations of Experiments 1 and 2 and demonstrated that these effects of context extinction were specific to backward-trained cues conditioned in the extinguished context. These results are interpreted in terms of cue-->context and context-->outcome associations.     

Associative and Normative Accounts of Negative Transfer

Subjects were given a prediction task in which they had to learn that one cue, P (positive), was followed by the outcome, and a compound of P and another cue, N (negative), was not followed by the outcome. Next, N was tested in compound with a transfer cue, T, which had signalled the outcome but had never been compounded with N. Experiment 1 confirmed an important assumption of the Rescorla-Wagner model (Wagner & Rescorla, 1972) that negation of T should depend on the specific P cue compound with N being positively contingent. Experiments 2 and 3 confirmed the model's prediction that no decrement in negative transfer should be observed following postlearning devaluation of P. Unfortunately, the model did not anticipate that a large proportion of devaluation trials relative to learning trials would attenuate negative transfer (Experiment 4), nor did it predict that negative transfer would occur when P was neutral during the learning stage and was only later made positive (Experiment 3). The results can be accommodated by the Rescorla-Wagner model if one assumes that absent cues have their associative strengths altered.