Latent inhibition and learned helplessness in children: Similarities and differences

Four experiments used a common set of procedures to investigate the occurrence and the generalization of learned helplessness (LH) and latent inhibition (LI) in 10- to 11-year-old children. In Experiment 1, preexposure to response-outcome independence impaired performance (i.e., LH) on two subsequent tests: The first was similar to the preexposure situation, the second was not. Moreover, LH occurred whether preexposure involved positive or negative feedback. On the other hand, noncontingent stimulus preexposure did not impair subsequent performance, i.e., LI was not obtained in the first experiment. Experiment 2 replicated the LH findings of Experiment 1: LH occurred following preexposure to response-independent feedback, regardless of whether that feedback was positive or negative, and LH generalized to a situation that was different from the preexposure situation. In addition, the stimulus preexposure procedures of Experiment 2 were embedded in a “masking” task and, under these conditions, LI was obtained. Nevertheless, LI did not generalize to a testing situation that was different from the preexposure situation. Experiment 3 demonstrated that noncontingent stimulus preexposure impairs performance relative to a nonpreexposed control group, that the effect is dependent upon masking, that masking alone produces no performance decrement, and that LI is, indeed, stimulus specific. In Experiment 4, preexposure to response-outcome independence impaired subsequent performance on similar and dissimilar tests whether feedback was consistently positive, consistently negative, or randomly positive and negative over trials. In addition, stimulus preexposure produced LI only under conditions of masking and even then, LI was not evident in novel test situations. The results are discussed in terms of common and different mechanisms underlying the LI and LH phenomena.     

An empirical analysis of the super-latent inhibition effect

In three conditioned taste aversion experiments, we examined the roles of several variables in producing super-latent inhibition (LI). This effect, greater LI after a long interval than after a short interval between the conditioning and the test stages (De la Casa & Lubow, 2000), was shown to increase with the number of stimulus preexposures (0, 2, or 4; Experiment 1) and with the length of the delay interval (1, 7, 14, or 21 days; Experiment 2). Furthermore, super-LI was obtained when the delay interval was introduced between the conditioning and the test stages (Experiments 1 and 2), but not when it was introduced between the preexposure and the conditioning stages (Experiment 3). The results are discussed in relation to interference explanations of LI.     

Delay-induced super-latent inhibition as a function of order of exposure to two flavours prior to compound conditioning

A number of recent conditioned taste aversion (CTA) experiments have demonstrated a super-latent inhibition (LI) effect—namely, a time-induced increase in the effects of stimulus preexposure when the interval between acquisition and test is spent in a context that is different from the other experimental contexts. Two CTA experiments with rats were conducted to examine the role of primacy in producing super-LI. In Experiment 1, one of two flavours was pre-exposed, following which a second flavour was preexposed. After the second preexposure, animals were conditioned by pairing a compound of the two preexposed flavours with LiCl. The test stage was conducted 1 or 21 days after conditioning, with the interval being spent in either the same or different contexts. In the test, animals were confronted with two bottles, each with one of the two preexposed flavours. Super-LI was obtained only for the first preexposed flavour in the 21-day delay group that spent the interval in a different context. Experiment 2 was designed to ensure that the effects in Experiment 1 represented LI, and to control for order of presentation of the flavours and time between preexposure and acquisition. The results replicated those of Experiment 1. The two experiments support the importance of primacy in the general super-LI experiment where CS-alone preexposure precedes CS-US.     

Latent inhibition of US signal value.

Three experiments with rats examined the effects of preexposure to an unconditioned stimulus (US; a single food pellet) on the subsequent ability of that US to effectively signal the delivery of three food pellets during a US-US conditioning procedure. In Experiment 1, latent inhibition (LI) rats showed attenuated conditioning, compared to control (C) rats, when a single food pellet, delivered 10 minutes into a session, was followed by three additional pellets. In preexposure, one pellet had been delivered 10 minutes into each session (in group LI), or placed into the magazine at the beginning of each session (in group C). Experiment 2 showed that this effect was evident when the conditions of preexposure matched those of conditioning for group C, and Experiment 3 showed that the difference between groups LI and C was not a product of context conditioning, or latent inhibition to the noise of the feeder in group LI. Implications of these results for theories of latent inhibition are considered.     

Latent inhibition: A trace conditioning phenomenon?

An informal model of latent inhibition (LI), the trace hypothesis, is described. This hypothesis holds that preexposure (PE) to the to-be-conditioned stimulus alters the salience (associability) of the CS such that only the onset and initial segments, but not the later segments, are capable of supporting conditioning when paired with a US. Thus, LI is effectively a trace conditioning phenomenon. Four experiments used rats and a one-trial fear-conditioning task to test predictions which stem from this hypothesis. Experiment 1 showed conditioning performance decreased as trace intervals increased between 0 and 12 s, thus demonstrating the sensitivity of this task to trace intervals proposed by the trace hypothesis to produce LI. Consistent with the trace hypothesis, LI was found to be an increasing function of the CS duration (Experiment 2), the number of PE trials (Experiment 3), and the US onset during a 15-s CS (Experiment 4). These data are somewhat problematic for several explanations of LI, but, in general, the trace hypothesis extends extant explanations by focusing on changes in salience within a given presentation of the CS.     

Priming and intrusion errors in RSVP streams with two response dimensions

Loach and Marí-Beffa (Vis Cogn, 10:513-526, 2003) observed that a distractor stimulus, presented immediately after a behaviorally relevant target stimulus, negatively primed a related probe stimulus indicating that the distractor had been inhibited. They argued that "post-target inhibition" may be a mechanism for preventing interference from temporally proximal stimuli; interference that could potentially result in a binding/intrusion error. In order to test this hypothesis, the authors carried out two rapid serial visual presentation (RSVP) experiments in which participants had to report either the identity (Experiment 1) or color (Experiment 2) of a target letter surrounded by distractor letters. In Experiment 1, a close relationship between priming and errors was observed. When a distractor stimulus showed evidence of being inhibited the participant was less likely to commit a binding error. The opposite was true when a distractor stimulus showed evidence of being facilitated. The results of Experiment 2 showed limited evidence of the same relationship.     

Latent Inhibition Depends on Inhibitory Attentional Learning to the Preexposed Stimulus: Evidence from Visual Search and Rule-Learning Tasks

Latent inhibition (LI) refers to findings of poorer learning with stimuli preexposed as irrelevant, compared to novel stimuli. In order to investigate the role of attention in traditional LI, two experiments with human subjects were conducted. Experiment 1 used a simplified visual-search design. As in previous studies, but now with a simpler design, there was a LI-like effect, thereby supporting the position that attentional learning to irrelevantly preexposed stimuli is reduced. Experiment 2 introduced conditions that were designed to exclude a potential contribution of novel popout to the visual-search LI-like effect. It was shown that the effect could be observed independently of contributions from novel popout. In addition, when participants were divided into good and poor attentional learners on the basis of visual-search LI scores, traditional rule-learning LI was established in good attentional learners, whereas it was absent in poor attentional learners. Together, these results indicate that visual-search procedures can be used to provide a measure for LI, and, as such, they support attention-based explanations of traditional LI.     

Some determinants of latent inhibition in human predictive learning

The present experiments assessed the effects of different manipulations between cue preexposure and cue-outcome pairings on latent inhibition (LI) in a predictive learning task with human participants. To facilitate LI, preexposure and acquisition with the target cues took place while participants performed a secondary task. Presentation of neither the target cues nor the target outcome was anticipated based on the instructions. Experiment 1 demonstrated the LI effect in the new experimental preparation. Experiment 2 analyzed the impact on LI of different activities that participants performed during the interval between preexposure and acquisition. Experiment 3 assessed LI as a function of changes in the secondary task cues made between preexposure and acquisition, namely presenting novel cues and reversing the cue-outcome contingencies. All of the manipulations in Experiments 2 and 3 resulted in a decrease in LI. The attenuation of LI by these manipulations challenges most current theories of learning and is best accommodated by Conditioned Attention Theory (Lubow, Weiner, & Schnur, 1981).     

Task demands and representation in long-term repetition priming

The effects of task demands on the representation of letter strings in long-term repetition priming (LTRP) were explored in two lexical decision experiments. The stimuli in both experiments were words and nonwords, some presented horizontally and some vertically. The only difference between the two experiments was the response required by the participant. In Experiment 1, the participants pressed one of two buttons, indicating whether or not a given stimulus was a word. In Experiment 2, the participants pressed one of four buttons, indicating both the lexical status and the orientation of a given stimulus. The results were that in Experiment 1, LTRP was not disrupted by a change in stimulus orientation, whereas in Experiment 2 it was, suggesting that the nature of the stimulus representation utilized in LTRP is partially dependent on the demands of the task.     

Human latent inhibition and the density of predictive relationships in the context in which the target stimulus occurs

In two experiments, participants were exposed to a listing of actions performed by a fictitious Mr. X, over three days of his life. For most of his actions an outcome was described, but some were not followed by any outcome. On Day 3, Mr. X performed an action (the target action) that was followed by a novel outcome. For participants in the control condition, the target action that preceded the appearance of this outcome was also novel; for participants in the latent inhibition (LI) condition, Mr. X had performed the target action on repeated occasions during Days 2 and 3, without it producing any outcome. All the participants were tested on their ability to retrieve the action performed by Mr. X prior to the target outcome. In Experiment 1, retrieval of the target action (indicating a less effective target action–outcome association) was poorer in the LI than in the control condition. In Experiment 2, reducing the proportion (the density) of nontarget actions that brought outcomes during initial training was found to reduce the size of the LI effect. These results are predicted by the account of LI put forward previously [Hall, G., & Rodríguez, G. (2010). Associative and nonassociative processes in latent inhibition: An elaboration of the Pearce-Hall model. In R. E. Lubow & I. Weiner (Eds.), Latent inhibition: Data, theories, and applications to schizophrenia (pp. 114–136). Cambridge, England: Cambridge University Press]. A high density of predictive relationships ensures strong activation of the expectancy that some outcome will occur when the target action is first presented; this facilitates the formation of a target action–no-event association during training in the LI condition, thus enhancing the LI effect.     

Influence of endogenous and exogenous orientations of attention on inhibition of return in a cross-modal target-target aiming task

The authors conducted 2 experiments in which participants (N = 16 in each) executed successive unimanual aiming movements to target locations that were indicated by the onset of either an auditory or a visual stimulus. In Experiment 1 (exogenous orientation), inhibition of return (IOR) effects were observed, with reliable reaction time (RT) costs associated with movements returning to the same target and a trend toward larger IOR effects in left than in right space. There was no influence of stimulus modality on the magnitude of IOR. IOR was also observed in Experiment 2 (endogenous orientation), except the influence of stimulus modality reliably mediated those effect. In that case, IOR was evident only when the previous modality was visual and the current modality was auditory. Together, the results of those 2 experiments suggest that in situations in which 2 paired movements constitute the response criteria, IOR is both supramodal and lateralized to contralateral space.     

Retroactive interference as a function of degree of interpolated study without overt retrieval practice

In two experiments, retroactive interference (RI) was examined under conditions designed to minimize retrieval-induced inhibition and output interference. In Experiment 1, the participants first learned a list of 10 person-location pairs, after which they viewed an interpolated list with the same person terms and different locations for one, four, or eight cycles. Learning was via a study-only method, so that the experimental participants did not perform instructed retrieval of the second list before a cued recall test that asked for List 1 locations only. The experimental participants in Experiment 2 received incidental learning instructions and then viewed a list of 20 unrelated words followed by another list presented either one or four times; the first two letters of each List 1 word were provided on the critical recall test. In both experiments, RI occurred and increased with degree of interpolation. The results suggest that RI does not require retrieval-induced inhibition.     

Control of reflexive and voluntary saccades in the gap effect

In two experiments, we examined whether voluntary and reflexive saccades shared a common fixation disengagement mechanism, Participants were required to perform a variety of tasks, each requiring a different level of information processing of the display prior to execution of the saccade. In Experiment 1, participants executed either a prosaccade or an antisaccade upon detecting a stimulus array. In Experiment 2, participants executed a prosaccade to a stimulus array only if the array contained a target item. The target could be a line (easy search) or a digit (difficult search). The critical manipulation in both experiments was the relative timing between the removal of the fixation stimulus and the onset of the stimulus array. In both experiments, it was found that saccadic latencies were shortest when the fixation stimulus was removed before the onset of the stimulus array—a gap effect. It was concluded that reflexive and voluntary saccades share a common fixation disengagement mechanism that is largely independent of higher level cognitive processes.     

Control' of reflexive and voluntary saccades in the gap effect.

In two experiments, we examined whether voluntary and reflexive saccades shared a common fixation disengagement mechanism. Participants were required to perform a variety of tasks, each requiring a different level of information processing of the display prior to execution of the saccade. In Experiment 1, participants executed either a prosaccade or an antisaccade upon detecting a stimulus array. In Experiment 2, participants executed a prosaccade to a stimulus array only if the array contained a target item. The target could be a line (easy search) or a digit (difficult search). The critical manipulation in both experiments was the relative timing between the removal of the fixation stimulus and the onset of the stimulus array. In both experiments, it was found that saccadic latencies were shortest when the fixation stimulus was removed before the onset of the stimulus array--a gap effect. It was concluded that reflexive and voluntary saccades share a common fixation disengagement mechanism that is largely independent of higher level cognitive processes.     

Does ignoring lead to worse evaluations? A new explanation of the stimulus devaluation effect

Affective evaluation of stimuli just seen in visual search tasks has been shown to depend on task-relevant stimulus configuration (Raymond, Fenske, & Tavassoli, 2003): Whereas targets and novel stimuli were evaluated similarly, distractors were devaluated. These results were explained by an inhibition-based account of the influence of selective attention on emotion. In the present experiments, we demonstrated that stimulus devaluation might not be a consequence of attentional inhibition. By simply instructing participants to react to an accepted or rejected stimulus in the visual search task of Experiment 1, we found distractor devaluation in the first case and target devaluation in the second case. We conclude that devaluation of stimuli is mediated by the affective connotation implied by response labels and instructions. This was confirmed in Experiment 2: To-be-ignored stimuli were not devaluated when participants knew that those stimuli would become task-relevant during the experiment.     

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.     

Loss of latent inhibition in conditioned taste aversion following exposure to a novel flavour before test

Killcross, Kiernan, Dwyer, andWestbrook (1998b) observed that latent inhibition(LI) of contextual fear was attenuated if animals received post-conditioning exposure to a novel context similar to the pre-exposure context. Six experiments used a conditioned taste aversion (CTA) procedure to examine this effect. Experiments 1A-1C demonstrated that LI of CTA was attenuated by a similar post-conditioning manipulation, establishing the generality of previous findings. Experiment 2A manipulated the taste elements to which animals were exposed after conditioning, revealing that exposure to a common element X, present at pre-exposure and conditioning, was not responsible for loss of LI. Experiment 2B manipulated test solution and showed that loss of LI depended on the presence of the full pre-exposed cue AX at test. These two results are contrary to predictions derived from the Dickinson-Burke (Dickinson & Burke, 1996) theory of retrospective revaluation or comparator theory (Miller & Matzel, 1988), and they support recent findings suggesting that retrospective effects may occur by several mechanisms. Experiment 3 showed that a novel element B had to be present during post-conditioning exposure for an attenuation of LI to be observed. Implications for the loss of LI following aretention interval between conditioning and test and retrieval-failure theories of LI are discussed.     

Formation of new stimulus equivalence classes by exclusion

This study presents three experiments that aimed to show the formation of stimulus equivalence relations among stimuli that had been previously related only by exclusion. In Experiment 1, participants were trained on baseline conditional discriminations to establish two 3‐member equivalence classes. Then, they were exposed to exclusion trials, without feedback, in which undefined stimuli had to be matched by rejecting the defined baseline stimuli. Finally, participants responded to test trials evaluating the emergence of symmetry and transitivity among the undefined stimuli from the exclusion trials. For half of the participants, the stimuli related by exclusion were introduced as S‐ stimuli in the baseline trials, whereas for the other half they were not. Further, half of the participants were assessed for emergent relations with stimuli from all the classes, whereas the other half was assessed for emergent relations with only the stimuli related by exclusion. In Experiment 2, the S‐ comparisons in the emergent relations test trials with stimuli only related by exclusion were stimuli from a null class. In Experiment 3, the number of exclusion trials was doubled. Across experiments, most participants showed emergence of equivalence relations among the stimuli related by exclusion. Some conditions of stimulus control associated with exclusion learning and the emergence of equivalence relations are discussed.     

Entorhinal but Not Hippocampal or Subicular Lesions Disrupt Latent Inhibition in Rats

Latent inhibition (LI) is the deficit of conditioning resulting from repeated nonreinforced preexposure to a conditioned stimulus before its pairing with an unconditioned stimulus. There are cumulative data showing that large lesions of the hippocampal formation disrupt LI. However, the effects of selective lesions of the different components of the hippocampal formation have never been directly addressed in the same study and conditioning paradigm. The first experiment of the present study aimed at investigating the effects of excitotoxic lesions of the hippocampus, subiculum, or entorhinal cortex on LI in an "off-baseline"-conditioned emotional response procedure. Hippocampus or subiculum lesions had no effect on either LI or conditioning. In contrast, entorhinal cortex lesions disrupted LI without modifying conditioning. In Experiment 2, locomotor activity in a novel environment was assessed in the same rats. Whereas lesions of hippocampus increased locomotor activity, lesions of the subiculum or the entorhinal cortex were devoid of effect. Although both LI and habituation to novel environmental cues are thought to involve interactions between the hippocampal formation and the mesolimbic pathway, these results indicate a functional dissociation between the hippocampus and the entorhinal cortex.     

Latent inhibition: The effects of ITI and CS intensity during preexposure

Two experiments are reported which test the effects of intertrial interval (ITI) and stimulus intensity during nonreinforced preexposure in the latent inhibition paradigm. In Experiment 1, using mice in an escape-avoidance task, latent inhibition was a direct function of the duration of stimulus intertrial interval during preexposure. In Experiment 2, using rats in a CER task, latent inhibition was a direct function of stimulus intensity during preexposure. These findings are discussed in terms of equivalent effects which have been reported in the habituation paradigm.