Mediated conditioning versus retrospective revaluation in humans: The influence of physical and functional similarity of cues

Two experiments assessed whether similarity between the two elements of a compound would influence the degree of mediated extinction versus recovery from overshadowing in human causal judgements. In both Experiments 1 and 2, we assessed the influence of extinguishing one element of a two-element compound on judgements about the other element. In Experiment 1 we manipulated the physical similarity of the two elements of the compound; in Experiment 2, we used equivalence and distinctiveness pretraining in order to vary their functional similarity. We found that these procedures influenced mediated extinction and recovery from overshadowing as a function of both physical and acquired similarity and distinctiveness, respectively. The implications of these results for previously reported differences between humans and nonprimate animals are discussed.     

Mediated conditioning and retrospective revaluation with LiCl then flavour pairings

It is becoming accepted that the associative strength of a cue can change in its absence, despite this being difficult to explain using existing theories of Pavlovian conditioning. To investigate the influence of timing on learning about the representation of an absent cue, lithium chloride (LiCl) or a flavour previously paired with LiCl was presented in a distinctive context that had previously been paired with a neutral target flavour. The former treatment produced an aversion to the target flavour whether the LiCl was presented 10 min before, or immediately after, exposure to the context. However, presenting the flavour associate of LiCl created an aversion to the target flavour only if it had been presented 10 min after LiCl during initial training. This pattern of results cannot be explained in the terms of a simple timing account, and it is proposed that an explanation will require different associative rules operating in simultaneous and successive training schedules.     

A comparison between elemental and compound training of cues in retrospective revaluation

Associative learning theories assume that cue interaction and, specifically, retrospective revaluation occur only when the target cue is previously trained in compound with the to-be-revalued cue. However, there are recent demonstrations of retrospective revaluation in the absence of compound training (e.g., Matute & Pine?o, 1998a, 1998b). Nevertheless, it seems reasonable to assume that cue interaction should be stronger when the cues are trained together than when they are trained apart. In two experiments with humans, we directly compared compound and elemental training of cues. The results showed that retrospective revaluation in the elemental condition can be as strong as and, sometimes, stronger than that in the compound condition. This suggests that within-compound associations are not necessary for retrospective revaluation to occur and that these effects can possibly be best understood in the framework of general interference theory.     

The effects of postconditioning revaluation of CS1 and UCS following pavlovian second-order electrodermal conditioning in humans

An experiment is described which uses various inferential post-conditioning revaluation techniques in order to clarify the associative substructure underlying Pavlovian electrodermal conditioning in human subjects. This study established a second-order skin conductance response (SCR) by pairing a CS₁ with an aversive 115 dB tone (UCS), and then pairing a different stimulus (CS₂) with CS₁. The second-order SCR survived post-conditioning extinction of the response to CS₁, but was abolished when (i) a post-conditioning habituation procedure resulted in a favourable revaluation of the tone UCS, or (ii) when subjects were given instructions which informed them that there would be no more UCS presentations. These results suggest that in the second-order electrodermal conditioning paradigm described, CR₂ is not mediated by S-R links--as it appears to be in second-order aversive conditioning in nonhuman animals--but is affected by manipulations which modify the subject's cognitions concerning the UCS.     

UCS revaluation and conditioning models of acquired fears

Recent developments in the study of Pavlovian conditioning in humans have suggested that the strength of a conditioned response (CR) is affected not only by associative processes that link the conditioned stimulus (CS) with the unconditioned stimulus (UCS), but also by processes which lead the individual to revalue the UCS itself. These latter processes can frequently lead to dramatic changes in CR strength independently of any experience with the CS-UCS contingency. This paper discusses a number of ways in which UCS revaluation can be effected in human subjects, and discusses their implications for conditioning models of acquired fears.     

Retrospective revaluation in humans: Learning or memory?

The phenomenon of retrospective revaluation has posed considerable problems for many associative learning theories as it involves a change in the associative strength of a cue on trials on which that cue is absent. The present series of experiments pursues this idea of changes in associative strength between evoked representations of cues, in an effort to establish, de novo, an excitatory connection between two cues simultaneously activated in memory. Given the finding of Dwyer, Mackintosh, and Boakes (1998) that simultaneous activation of absent cues in the memory of rats resulted in learning comparable to that seen inretrospective revaluation, we expected that if retrospective revaluation was found in humans, then excitatory learning due to simultaneous activation would also be seen. This was not the case. The implications of our results are discussed in terms of Dickinson and Burke's (1996) modified SOP model and a version of McLaren's (1993) APECS network. We conclude that many of the effects attributed to learning in retrospective revaluation studies are better thought of as due to changes in the retrievability of items in memory.     

Aging and retrospective revaluation of causal learning

In a 2-stage causal learning task, young and older participants first learned which foods presented in compound were followed by an allergic reaction (e.g., STEAK-BEANS→ REACTION) and then the causal efficacy of 1 food from these compounds was revalued (e.g., BEANS→ NO REACTION). In Experiment 1, unrelated food pairs were used, and although there were no age differences in compound- or single-cue-outcome learning, older adults did not retrospectively revalue the causal efficacy of the absent target cues (e.g., STEAK). However, they had weaker within-compound associations for the unrelated foods, and this may have prevented them from retrieving the representations of these cues. In Experiment 2, older adults still showed no retrospective revaluation of absent cues even though compound food cues with pre-existing associations were used (e.g., STEAK-POTATO), and they received additional learning trials. Finally, in Experiment 3, older adults revalued the causal efficacy of the target cues when small, unobtrusive icons of these cues were present during single-cue revaluation. These findings suggest that age-related deficits in causal learning for absent cues are due to ineffective associative binding and reactivation processes.     

Negative anticipatory contrast and preference conditioning: flavor cues support preference conditioning, and environmental cues support contrast.

In 2 experiments, access to a 0.15% saccharin solution was followed on alternating days by access to a 32% sucrose solution and the same saccharin solution. In Experiment 1, rats increased both intake of and preference for a flavored saccharin solution that predicted sucrose, but neither effect was found using a predictive odor cue alone. Experiment 2 replicated the predictive flavor results but showed suppression of saccharin intake when environmental cues predicted sucrose. When both flavor and environment predicted sucrose, saccharin intake did not change, but preference for the predictive flavor increased. Discriminative taste cues appear to facilitate the development of preference conditioning, but environmental cues favor negative anticipatory contrast effects. Also, preference conditioning and contrast may develop concurrently and compete for expression.     

Stimulus and temporal cues in classical conditioning

In 2 experiments, separate groups of rats were given stimulus conditioning, temporal conditioning, untreated control and (in Experiment 2) learned irrelevance control procedures, followed by a compound with both stimulus and temporal cues. Stimulus conditioning consisted of a random 15-s duration conditioned stimulus (CS) followed by food; temporal conditioning consisted of food-food intervals of fixed 90 s (Experiment 1) or fixed 75 + random 15 s (Experiment 2). The stimulus group abruptly increased responding after CS onset, and the temporal group gradually increased responding over the food-food interval. When the food-food interval was fixed 90 s, the temporal cue exerted stronger control in the compound, whereas when the food-food interval was fixed 75 + random 15 s, the stimulus cue exerted stronger control. The strength of conditioning, temporal gradients of responding, and cue competition effects appear to reflect simultaneous timing of multiple intervals.     

Perceptual learning enhances retrospective revaluation of conditioned flavor preferences in rats

Forward and backward blocking of taste preference learning was compared in rats. In the forward condition, thirsty rats were exposed to a flavor (A) in sucrose solution (+) or in water (-), after which they were exposed to A in compound with another flavor (B) in sucrose solution (i.e., AB+). In the backward condition, these phases were reversed. Consumption of B alone was assessed when rats were food deprived. In the forward condition, rats given A+ consumed less B than rats given A-, providing evidence of forward blocking, whereas in the backward condition, rats given A+ drank more of B than those given A-. Subsequent experiments found that alternating but not blocked preexposure to A and B, when given prior to training, produced blocking of B whether A+ was given before or after AB+, suggesting that prior failures to observe backward blocking reflect failures of discrimination.     

Within-compound associations in retrospective revaluation and in direct learning: A challenge for comparator theory

In three human causal learning experiments we investigated the role of within-compound associations in learning about absent cues versus learning about present cues. Different theoretical approaches agree that within-compound associations are essential for learning about absent cues-that is, for retrospective revaluation. They differ, however, with regard to the role of within-compound associations for learning about present cues-that is, for direct learning. A memory test was used to assess within-compound associations. Experiment 1 used a blocking/release from overshadowing design, Experiment 2 used a conditioned inhibition design, and Experiment 3 used a higher-order cue selection design. In all experiments, first-order retrospective revaluation was significantly correlated with within-compound associations, but no significant correlations were found for the direct learning conditions. In addition to this, second-order retrospective revaluation in Experiment 3 was positively correlated to joint knowledge of first-order and second-order within-compound associations. Furthermore, cue selection effects were stronger for direct learning conditions than for retrospective learning conditions. These results are at variance with the comparator hypothesis but are in agreement with a modified associative theory and with the suggestion that retrospective revaluation might be due to rehearsal processes.     

Re-examination of the role of within-compound associations in the retrospective revaluation of causal judgements

We investigated blocking and retrospective revaluation of causal judgements using a scenario in which food cues acted as potential causes of an allergic reaction as the outcome. In the blocking contingency,the treatment cues were either paired or unpaired with the outcome prior to a second stage in which sequential compounds of treatment and target cues were paired with the outcome. The order of this compound and treatment training was reversed in retrospective revaluation contingencies. When the interstimulus interval between the treatment and target cues was unfilled on compound trials (Experiments 1 and 3), both blocking and retrospective revaluation were observed in that the target cue trained in compound with the paired treatment cue attracted lower causal ratings than the target cue trained in compound with the unpaired treatment cue. By contrast, performing a mental arithmetic task using numerals presented during the interstimulus interval had no effect on the magnitude of blocking but rendered retrospective revaluation unreliable (Experiments 2 and 3). These results provide further support for accounts of revaluation based upon within-compound associations.     

Causal beliefs and conditioned responses: retrospective revaluation induced by experience and by instruction

The author tested causal beliefs and conditioned responses in a task involving retrospective revaluation of the causal status of a target cue with respect to electric shock. Successful revaluation was observed on both self-report shock expectancy and skin conductance, whether the training trials were directly experienced, described, or partly experienced and partly described. The results contradict models that link anticipatory conditioned responses to a separate or earlier process from that underlying explicit causal knowledge. They suggest instead that a single learning process gives rise to propositional knowledge that (a) drives anticipatory responding, (b) forms the basis for self-reported causal beliefs, and (c) can be combined with other knowledge, provided either by experience or symbolically, to generate inferences such as retrospective revaluation.     

The control dilemma in eating behavior: influence of temptation cues in restrained versus unrestrained eaters

The present research explored the effects of pre-exposure to temptation primes and dieting primes on food intake, goal accessibility and explicit automatic evaluations of food-enjoyment and dieting goals among restrained and unrestrained eaters. Participants (n= 166) were randomly assigned to three conditions: food-cue, dieting, or control, in which they were exposed to incidental presentation of gourmet, fashion or geographic magazines, respectively. Words related to the goals of dieting and/or food- enjoyment were presented in a computer decision task following the incidental presentation of gourmet, dieting, and geographic magazine photographs. The computer task and the presentation of food were counterbalanced. Participants' food intake was assessed in a taste-rating task. Restrained eaters ate more than did unrestrained eaters across the three conditions. Restrained eaters who were exposed to food cues ate more than did restrained eaters in the control condition and they evaluated the goal of dieting more negatively compared to restrained eaters in the other two conditions. These findings were inconsistent with 'Counteractive Self-Control Theory' but consistent with previous studies on the effects of food-cue exposure in restrained eaters.     

The basic laws of conditioning differ for elemental cues and cues trained in compound

The cue-duration effect (i.e., longer cues result in less conditioned responding than shorter cues) was examined as a function of whether cues were trained alone or in compound. Compound (AX) or elemental (X) cues of either long or short duration were paired with the unconditioned stimulus. In testing with X alone, the cue-duration effect was observed with elementally trained cues, but not with compound cues. Instead, stronger responding resulted from training with long compound cues relative to short compound cues (i.e., a reversed cue-duration effect). Moreover, an overshadowing effect (i.e., decreased responding due to compound conditioning) was observed when conditioning was conducted with a short cue, but compound conditioning resulted in enhanced responding when it was conducted with a long cue (i.e., reversed overshadowing). These findings are consistent with other recent demonstrations that some laws of learning that apply to elementally trained cues do not similarly apply to cues trained in compound.     

Birds of a feather and birds flocking together: physical versus behavioral cues may lead to trait- versus goal-based group perception

Entitativity perception refers to the perception of a collection of individuals as a group. The authors propose 2 perceptual-inferential bases of entitativity perception. First, perceivers would expect a collection of individuals with similar physical traits to possess common psychological traits. Second, perceivers watching a group of individuals engage in concerted behavior would infer that these individuals have common goals. Thus, both similarity in physical traits (e.g., same skin color) and concerted collective behavior (e.g., same movement) would evoke perception of group entitativity. Results from 5 experiments show that same group movement invariably leads to common goal inferences, increased perceived cohesiveness, and increased perceived entitativity. Moreover, same skin color evokes inferences of group traits and increases perceived homogeneity and perceived entitativity but only when skin color is diagnostic of group membership.     

Inference-based retrospective revaluation in human causal judgments requires knowledge of within-compound relationships

In an allergist causal-judgment task, food compounds were followed by an allergic reaction (e.g., AB+), and then 1 cue (A) was revalued. Experiment 1, in which participants who were instructed that whatever was true about one element of a causal compound was also true of the other, showed a reverse of the standard retrospective revaluation effect. That is, ratings of B were higher when A was causal (A+) than when A was safe (A-). This effect was taken to reflect inferential reasoning, not an associative mechanism. In Experiment 2, within-compound associations were found to be necessary to produce this inference-based revaluation. Therefore, evidence that within-compound associations are necessary for retrospective revaluation is consistent with the inferential account of causal judgments.