Associative interference with taste aversions after contextual discrimination learning

In two experiments, rats were first given discriminative training with two distinctive contexts, such that a flavor was paired with lithium chloride (LiCl) in one context, alternating with presentations of the flavor alone in another context. Contextual control of the fluid ingestion was observed in that rats reduced the fluid intake in the LiCl-paired context but drank the solution in the context never paired with lithium. Having learned this discrimination, the rats were now given a second flavor in their home cage before being injected with LiCl and transferred to the previously lithium-paired context. In Experiment 1, the acquisition of an aversion to the novel flavor was blocked when this flavor and the contextual cues are conditioned as a compound. In Experiment 2, the blocking effect and the conditional control over fluid consumption were abolished when the associative strength of the LiCl-paired context had been extinguished by exposing the animals to water in the contexts after discriminative training. These results are interpreted as evidence that context dependency of conditioned taste aversions is mediated by a summative effect of the context–LiCl and flavor–LiCl associations.     

The influence of context and UCS intensity on the UCS preexposure effect in a flavor aversion paradigm

Three studies were conducted to evaluate the influence of environmental context and UCS preexposure intensity on the acquisition of a flavor aversion. In the first study, rats were exposed to two UCS-alone presentations at one of three dose levels of LiCl. The rats were given the two UCS preexposures in one of two contexts (familiar or novel). Following the UCS-alone treatment, all of the subjects received two pairings of sucrose and LiCl (1.25 meq) in the familiar context. Animals receiving UCS preexposures in the same context as used during conditioning consumed significantly more sucrose than did saline control animals. In contrast, the influence of prior UCS preexposure was not evident when UCS preexposure was experienced in a context different from that experienced during conditioning. In Experiment 2, all animal received UCS preexposure and conditioning in the novel room. Animals received either two or four preexposures at 0, 1.25, or 3.75 meq dose of LiCl. Two UCS preexposures at 3.75 meq dose produced a stronger UCS preexposure effect than did the 1.25 meq dose. Animals in Experiment 3 received two exposures to either 0-, 1.25-, or 3.75-meq LiCl in one of two contexts, followed by conditioning with the 1.25-meq LiCl dose in the same context as preexposure. Greater UCS interference occurred in animals preexposed to LiCl in the novel rather than familiar environment, with no specific dose effects in either context. These observations are discussed in terms of context blocking and generalization decrement models of the UCS preexposure effect.     

Taste aversion after ingestion of lithium chloride: An associative analysis

In five experiments with rats we examined the aversion established by consumption of a solution of lithium chloride (LiCl). Experiment 1 showed that consumption of LiCl established an aversion to saline (NaCl). Experiment 2 showed that the size of the aversion was reduced in rats given pre-exposure to saline (a latent inhibition effect). Experiment 3 showed that experience of a sucrose-saline compound prior to consumption of LiCl generated an aversion to sucrose (a sensory preconditioning effect). Experiments 4 and 5 examined the effects produced by consumption of a sucrose-LiCl compound and demonstrated reciprocal overshadowing between the two tastes. These results confirm that consumption of LiCl establishes an aversion to the taste of this substance. Their implications for the use of orally consumed LiCl as a technique for the control of predatory behaviour are discussed.     

Context specificity of latent inhibition in taste aversion learning

In three experiments rats were given injections of LiCl after consuming distinctively flavoured water. The rats developed an aversion to the flavour and in all experiments the magnitude of the aversion was found to be reduced in subjects that had received pre-exposure to the flavour without aversive consequences. Experiment 1 demonstrated this pre-exposure effect to be a case of latent inhibition. The remaining experiments investigated the effects of pre-exposing the flavour in a context different from that used for conditioning. It was found (Experiment 2) diat latent inhibition transferred perfectly when the context change consisted of a move from one home cage to another. Context specificity of latent inhibition was found (Experiment 3) only when the subjects were given daily sessions in die experimental contexts, these being cages different from the home cage.     

The US-preexposure effect in lithium-induced flavor-aversion conditioning is a consequence of blocking by injection cues

In 2 experiments, rats received flavor-aversion conditioning in which the unconditioned stimulus (US) was an orally consumed solution of lithium chloride (LiCl). The resulting aversion was not attenuated by giving preexposure to injections of LiCl, although such preexposure did attenuate aversions established using injected LiCl as the US (Experiment 1). This outcome suggests that blocking by injection-related cues is responsible for the US-preexposure effect observed in this situation. Experiment 2 confirmed this interpretation by showing that presenting such cues (by giving an injection of saline) at the time that the LiCl was drunk resulted in an attenuation of conditioning in animals preexposed to injections of LiCl. The US-preexposure effect obtained in these experiments can be explained solely in terms of blocking by injection cues, although other mechanisms may contribute to the effect seen in other flavor-aversion paradigms.     

Signalling and incentive processes in instrumental reinforcer devaluation

We have previously reported that conditioning an aversion to the reinforcer using an isotonic lithium chloride (LiCl) solution following instrumental training reduces performance in a subsequent extinction test only if animals are re-exposed to the reinforcer prior to the test. Rescorla (1992), in contrast, reported an immediate devaluation effect using a hypertonic LiCl solution that did not depend upon re-exposure. In two experiments we examined the effect of using a hypertonic LiCl solution to condition the aversion to the reinforcer on subsequent instrumental performance in extinction, with and without re-exposure. In Experiment 1 thirsty rats were trained to press a lever for a sucrose solution before being injected with 0.6 M LiCl either immediately or after a delay. Half of the immediate and delay groups were then re-exposed to the sucrose in the absence of the lever, with the remainder being exposed to water. Contrary to the previously reported effects of isotonic LiCl, a hypertonic solution induced a reinforcer devaluation effect in all the immediately poisoned animals, which did not depend upon re-exposure to the reinforcer. In Experiment 2 the possibility that this devaluation effect was induced by the discomfort associated with the hypertonicity of the solution was assessed by replicating Experiment 1 but, in addition, using two immediately poisoned groups given the LiCl injection under anaesthesia. In the absence of anaesthesia, the devaluation effect observed without re-exposure to the reinforcer in Experiment 1 was replicated. When the injection was given under anaesthesia, however, a reinforcer devaluation effect was observed only in animals that were re-exposed to the reinforcer prior to the extinction test. These results were interpreted as evidence that a reinforcer devaluation effect induced by pairing the reinforcer with illness depends upon a process of incentive learning, whereas a devaluation effect mediated by learning a signalling relationship between the reinforcer and somatic discomfort does not.     

Processing category terms in context: instantiation and the structure of semantic categories

The present study sought to determine if semantic categories processed in context are encoded as particular exemplars. In Experiment 1 we replicated previous results on an extended and modified set of stimuli by showing that when subjects read sentences containing a category term in a context designed to bias encoding toward an atypical exemplar, the atypical exemplar serves as a better retrieval cue than a typical exemplar. In Experiment 2 we tested whether these cued-recall results were due to processes operating at encoding or retrieval. The pattern of semantic interference obtained in a modified Stroop paradigm clearly contradicted the position that readers routinely encode general terms as examples, or "instantiations." In particular, there was significant color-naming interference when typical exemplars served as targets even when preceded by sentences designed to bias encoding toward an atypical exemplar. No significant color-naming interference was generated to atypical exemplars. Experiment 3 ruled out the possibility that differences between the cued-recall and Stroop results in the first two experiments were due to encoding strategy differences. It was concluded that assigning a referent to a category term is not a routine activity in sentence encoding and that processing category terms entails activation of summary representations.     

Examination of factors which might disrupt a learned association between pentobarbital and LiCl

Injections of a sedative dose of pentobarbital (Pent) were followed 30 min later by injections of a toxic dose of lithium chloride (LiCl). As a result of these Pent →LiCl pairings, injections of Pent after consumption of saccharin solution failed to produce the usual saccharin aversion. This loss of the capacity of Pent to produce a flavor aversion is called Avfail. Experiment 1 showed that the Avfail effect was obtained with saccharin even though the rats consumed a novel vinegar solution prior to the Pent→LiCl pairings in Phase 1. This was surprising since the novel flavor was associated with the LiCl and ought to have overshadowed the association of Pent with LiCl. Experiment 2 showed that one set of Pent→LiCl pairings can produce two Avfail effects in sequence: the first with a novel flavor and the second with a flavor previously paired with LiCl sickness. It also showed that insertion of Pent injections and handling cues between the Pent→LiCl and the Flavor→Pent phases did not reduce the magnitude of Avfail. Experiment 3 showed that the Avfail effect was not disrupted by the insertion of 54 saline injections between the Pent→LiCl and Flavor→Pent pairings, nor by interposing 26 saline injections between each pair of Flavor→Pent trials. This seemed to exclude an important role for injection cues. Experiment 3 also showed that 4 exposures to Pent and 50 exposures to saline between the Pent→LiCl trials and the Flavor→Pent trials and 26 exposures to saline injections between each pair of Flavor→Pent trials did not reduce the magnitude of Avfail. The same exposure to Pent and saline injections did reduce the magnitude of the saccharin aversion shown by the LiCl→Pent group. These data are viewed as consistent with Lett's (Drug-drug associations: Evidence for the conditioning of a compensatory response. Paper presented at a meeting of the Eastern Psychological Association, New York, 1981) suggestion that Avfail represents a learned antisickness response.     

Superlatent inhibition and spontaneous recovery: differential effects of pre- and postconditioning CS-alone presentations after long delays in different contexts

In two pairs of three-stage conditioned taste aversion experiments, we examined the effects of delay interval (1 or 21 days) between the second and third stages, and of context in which the animals spent the delay (same as or different from the context of the other stages) on latent inhibition (LI) and spontaneous recovery following extinction. In the LI experiments (Experiments 1A and 1B), the first stage comprised nonreinforced presentations to saccharin or to water. In the second stage, rats were conditioned by saccharin paired with LiCl. In the extinction experiments (Experiments 2A and 2B), the order of the stages was reversed. For all experiments, Stage 3, the test stage, consisted of three presentations of saccharin alone. There was a super-LI effect in the saccharin-preexposed group that spent the 21-day delay in the different context (Experiment 1A). When the delay was spent in the same context, there was no difference in the amount of LI between the short- and long-delay groups (Experiment 1B). Conversely, there was a spontaneous recovery effect in the long-delay/same-context group (Experiment 2B), but not in the long-delay/different-context group (Experiment 2A). The pattern of results, incompatible with current explanations of delay-induced changes in memory performance, was interpreted in terms of an interaction between the delay conditions (same or different delay context), which modulate the extinction of previously acquired context-CS-nothing associations (during CS-alone presentations), and primacy effects.     

Investigating the role of response in spatial context learning

Recent research has shown that simple motor actions, such as pointing or grasping, can modulate the way we perceive and attend to our visual environment. Here we examine the role of action in spatial context learning. Previous studies using keyboard responses have revealed that people are faster locating a target on repeated visual search displays ("contextual cueing"). However, this learning appears to depend on the task and response requirements. In Experiment 1, participants searched for a T-target among L-distractors and responded either by pressing a key or by touching the screen. Comparable contextual cueing was found in both response modes. Moreover, learning transferred between keyboard and touch screen responses. Experiment 2 showed that learning occurred even for repeated displays that required no response, and this learning was as strong as learning for displays that required a response. Learning on no-response trials cannot be accounted for by oculomotor responses, as learning was observed when eye movements were discouraged (Experiment 3). We suggest that spatial context learning is abstracted from motor actions.     

Investigating the role of response in spatial context learning

Recent research has shown that simple motor actions, such as pointing or grasping, can modulate the way we perceive and attend to our visual environment. Here we examine the role of action in spatial context learning. Previous studies using keyboard responses have revealed that people are faster locating a target on repeated visual search displays (“contextual cueing”). However, this learning appears to depend on the task and response requirements. In Experiment 1, participants searched for a T-target among L-distractors and responded either by pressing a key or by touching the screen. Comparable contextual cueing was found in both response modes. Moreover, learning transferred between keyboard and touch screen responses. Experiment 2 showed that learning occurred even for repeated displays that required no response, and this learning was as strong as learning for displays that required a response. Learning on no-response trials cannot be accounted for by oculomotor responses, as learning was observed when eye movements were discouraged (Experiment 3). We suggest that spatial context learning is abstracted from motor actions.     

Implicitly activated memories are associated to general context cues

Words having more densely entangled associative structures are more likely to be recalled in the presence of related extralist cues. A context-modified PIER2 model predicts that the implicit activation of such structures during study connects them to the context of the learning episode. In two experiments, we evaluated this assumption by varying the associative density of the study words and the accessibility of context information. In Experiment 1, we varied context accessibility by manipulating context awareness and by delaying testing and filling the delay with different types of interfering tasks. In Experiment 2, we varied accessibility by manipulating test delay and type of interference in a factorial design. The effects of associative density were reduced by using implicit testing that never refers to context, by performing interpolated interference tasks, and finally, by extending the length of the delay. Information that is implicitly activated during an episodic experience is associated to the context of that experience.     

Conditioned taste aversion is enhanced when the unconditioned stimulus is presented in a different context

Using a conditioned taste aversion procedure with rats as the subjects, two experiments examined the effect of presenting a conditioned stimulus (CS saccharin solution) in one context followed by an unconditioned stimulus (US LiCl) in a different context. Experiment 1 showed that animals which received the above-mentioned procedure (Group D) showed a more marked conditioned aversion to the CS than animals which were given both the CS and the US in the same context (Group S). Experiment 2 found that in both Group D and Group S, aversion to the CS increased when the subjects were exposed to the conditioned context after the conditioning. These findings supported the argument that the strength of the CS-US association acquired during conditioning is compared with that of the context-US to determine the magnitude of aversion revealed to the CS.     

拖延刺激对注意偏向的影响及过程

研究是考察拖延个体对拖延相关信息的注意偏向及特点。实验1采用情绪Stroop范式,要求被试忽略刺激的语义,仅判断刺激的颜色。实验2采用修改后的点探测范式,以拖延词和中性词为线索,并操作线索和目标之间的时间间隔,被试的任务是判断目标刺激的位置。结果发现:高拖延的被试难以抵制拖延词的注意,在情绪Stroop任务中对拖延词的反应时间更长; 当拖延词和目标刺激的位置一致时,在短的线索—目标时间间隔(SOA)内,被试对目标刺激的反应时间更长,但当时间间隔长时,一致条件下的反应时更短。该研究表明,高拖延行为个体在有限的时间内难以抵制拖延信息的注意,对拖延刺激存在注意偏向。     

Estimating the valence of single stimuli: a new variant of the Affective Simon Task

In this article, a modified variant of the Affective Simon Task (AST; De Houwer & Eelen, 1998) is presented as a measure of implicit evaluations of single stimuli. In the AST, the words "good" or "bad" have to be given as responses depending on the color of the stimuli. The AST was combined with an evaluation task to increase the salience of the valence of the presented stimuli. Experiment 1 investigated evaluations of schematic faces showing emotional expressions. In Experiment 2 we measured the valence of artificial stimuli that acquired valence in a game context during the experiment. Both experiments confirm the validity of the modified AST. The results also revealed a dissociation between explicit and implicit evaluations.     

Associative effects of US preexposure: modulation of conditioned responding by an excitatory training context

In two experiments we examined factors that contribute to retarded emergence of conditioned responding to a conditioned stimulus (CS) trained in a context in which unsignaled unconditioned stimuli (USs) had previously been administered. In both experiments water-deprived rats were used in a conditioned lick suppression task to measure the conditioned response elicitation potential of the CS and the training context. From Experiment 1 we determined that nonreinforced exposure to the excitatory context after US preexposure and prior to CS-US pairings in that context eliminated the conditioned response deficit observed on a subsequent test of the CS. The recovery from the US preexposure deficit was nearly as great in animals that received nonreinforced exposure to the excitatory training context after the CS-US pairings but prior to the ultimate test of the CS. From Experiment 2 we determined that the recovery induced by contextual deflation after CS training was specific to deflation of the context in which the CS was trained as opposed to another excitatory context. In total, these experiments suggest that context-US associations partially mask the expression of a learned CS-US association. These results are discussed in terms of recent models of conditioned response generation.     

Ease of processing constrains the activation flow in the conceptual-lexical system during speech planning

In 3 picture-word interference experiments, speakers named a target object in the presence of an unrelated not-to-be-named context object. Distractor words, which were phonologically related or unrelated to the context object's name, were used to determine whether the context object had become phonologically activated. All objects had high frequency names, and the ease of processing of these objects was manipulated by a visual degradation technique. In Experiment 1, both objects were nondegraded; in Experiment 2, both objects were degraded; and in Experiment 3, either the target object or the context object was degraded. Distractor words, which were phonologically related to the context objects, interfered with the naming response when both objects were nondegraded, indicating that the context objects had become phonologically coactivated. The effect vanished when both objects were degraded, when only the context object was degraded, and when only the target object was degraded. These data demonstrate that the amount of available processing resources constrains the forward cascading of activation in the conceptual-lexical system. Context objects are likely to become phonologically coactivated if they are easily retrieved and if prioritized target processing leaves sufficient resources.     

Potentiation of odor by taste in rats: tests of some nonassociative factors

The contribution of nonassociative neophobia and sensitization to the potentiation of odor by taste in rats was tested in three experiments. In Experiment 1, neophobia for almond odor (O), saccharin taste (T), and odor-taste compound (OT) cues was tested before and after noncontingent lithium chloride poisoning and compared with conditioned aversions produced by OT-LiCl temporal pairing. The OT compound potentiated unconditioned neophobia, but there was no evidence of poison-enhanced neophobia, disinhibition of neophobia, or sensitization by noncontingent LiCl; temporal pairing produced aversions for the compound and its elements. In Experiment 2, generalization to a novel odor was tested after O-LiCl or compound OT-LiCl pairing. The potentiated odor aversion did not generalize to the novel odor; it was specific to the odor paired with taste and LiCl. In Experiment 3, potentiation of the odor component by a discriminant or nondiscriminant taste component was tested. Potentiation was evident only when a novel discriminant taste was in compound with odor prior to LiCl poisoning. These studies support an associative "indexing" hypothesis of the potentiation effect in rats.     

Instrumental Outcome Devaluation Is Attenuated by the Anti-emetic Ondansetron

In three experiments we assessed the effect of an anti-emetic, the selective S-HT antagonist ondansetron, on (1) the conditioning of a taste aversion using lithium chloride (LiCl); (2) the expression of that aversion; and (3) instrumental outcome-devaluation effects. In Experiment 1 it was found that ondansetron reduced the aversion induced by LiCl when administered prior to the LiCl injection and also attenuated the expression of that aversion when administered prior to test sessions. In Experiments 2 and 3, thirsty rats were trained, in a single session, to lever press and chain pull for sucrose and saline solutions concurrently before being injected with LiCl. They were then re-exposed to both solutions, one after injection of vehicle and the other after injection of ondansetron. In a choice extinction test on the levers and chains, animals performed more of the action whose training outcome was re-exposed under ondansetron than the other action, whether the test was conducted after an injection of vehicle or after one of ondansetron.     

Taboo words: The effect of emotion on memory for peripheral information

In three experiments, we examined memory for peripheral information that occurred in the same context as emotion-inducing information. In the first two experiments, participants studied either a sentence (Experiment 1) or a pair of words (Experiments 2A—2C) containing a neutral peripheral word, as well as a neutral, negative-valence, or taboo word, to induce an emotional response. At retrieval, the participants were asked to recall the neutral peripheral word from a sentence fragment or emotion-inducing word cue. In Experiment 3, we presented word pairs at encoding and tested memory with associative recognition. In all three experiments, memory for peripheral words was enhanced when it was encoded in the presence of emotionally arousing taboo words but not when it was encoded in the presence of words that were only negative in valence. These data are consistent with priority-binding theory (MacKay et al., 2004) and inconsistent with the attention-narrowing hypothesis (Easterbrook, 1959), as well as with object-based binding theory (Mather, 2007).