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). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An inhibitory within-compound association attenuates overshadowing.

According to the comparator hypothesis (Miller & Matzel, 1988), cue competition depends on the association between a target stimulus (X) and a competing cue (e.g., an overshadowing cue [A]). Thus, it was expected that overshadowing would be reduced by establishing an inhibitory-like relationship between X and A before compound conditioning. In three lever press suppression experiments with rats, this expectation was supported. Experiment 1 showed that establishing an inhibitory X-A relationship reduced overshadowing. In Experiment 2, degrading the inhibitory-like relationship before conditioning allowed reinforced AX compound trials to result in overshadowing. Experiment 3 replicated the results of Experiment 2 when the inhibitory relationship was degraded after compound conditioning. The results support the view that within-compound associations are necessary not only for retrospective revaluation, but also for conventional cue competition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrasting predictions of extended comparator hypothesis and acquisition-focused models of learning concerning retrospective revaluation.

Three conditioned suppression experiments with rats investigated contrasting predictions made by the extended comparator hypothesis and acquisition-focused models of learning, specifically, modified SOP and the revised Rescorla–Wagner model, concerning retrospective revaluation. Two target cues (X and Y) were partially reinforced using a stimulus relative validity design (i.e., AX–Outcome; BX–No outcome; CY–Outcome; DY–No outcome), and subsequently one of the companion cues for each target was extinguished in compound (BC–No outcome). In Experiment 1, which used spaced trials for relative validity training, greater suppression was observed to target cue Y for which the excitatory companion cue had been extinguished in relation to target cue X for which the nonexcitatory companion cue had been extinguished. Experiment 2 replicated these results in a sensory preconditioning preparation. Experiment 3 massed the trials during relative validity training, and the opposite pattern of data was observed. The results are consistent with the predictions of the extended comparator hypothesis. Furthermore, this set of experiments is unique in being able to differentiate between these models without invoking higher-order comparator processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Massed extinction trials produce better short-term but worse long-term loss of context conditioned fear responses than spaced trials.

A series of experiments studied the effects of the interval between extinction trials on the loss of context conditioned freezing responses. Rats were shocked in one context (A) but not in another (B) and subjected to extinction trials in context A. In Experiment 1, massed trials produced more rapid loss than spaced trials. A shift from spaced to massed trials maintained this loss, but the shift from massed to spaced trials restored lost responses. Experiments 2-5 examined this effect of massed trials on responding across spaced trials. They provided evidence that (a) a single trial was as effective as multiple daily massed trials, (b) learning occurred on the first of the massed trials but not on later ones, and (c) the first trial reduced the amount learned across subsequent massed trials. Finally, alternating extinction trials in A and B produced more response loss across spaced trials than blocks of trials in A and B. The results were discussed in terms of the role accorded to self-generated priming in the models developed by A. R. Wagner (1978, 1981). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The temporal dynamics of a visual discrimination: The role of stimulus comparison and opponent processes.

The influence of trial spacing on simple conditioning is well established: When successive reinforced conditioned stimulus, CS+, trials are separated by a short interval (massed training), conditioned responding emerges less rapidly than when such trials are separated by longer intervals (spaced training). This study examined the influence of trial spacing on the acquisition of an appetitive visual discrimination in rats. Experiments 1 and 2 established that massed training facilitates the acquisition of such discriminations. The results of subsequent experiments demonstrated that this trial-spacing effect reflects the proximity of nonreinforced, CS-, trials to preceding (Experiment 3) and signaled (Experiment 4) presentations of the reinforcer. Experiment 5 showed that the facilitation of discrimination learning with massed training reflected an effect on learning rather than performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rehearsal strategies can enlarge or diminish the spacing effect: Pure versus mixed lists and encoding strategy.

Using 5 experiments, the authors explored the dependency of spacing effects on rehearsal patterns. Encouraging rehearsal borrowing produced opposing effects on mixed lists (containing both spaced and massed repetitions) and pure lists (containing only one or the other), magnifying spacing effects on mixed lists but diminishing spacing effects on pure lists. Rehearsing with borrowing produced large spacing effects on mixed lists but not on pure lists for both free recall (Experiment 1) and recognition (Experiment 2). In contrast, rehearsing only the currently visible item produced spacing effects on both mixed lists and pure lists in free recall (Experiment 3) and recognition (Experiment 4). Experiment 5 demonstrated these effects using a fully within-subjects design. Rehearse-aloud protocols showed that rehearsal borrowing redistributed study from massed to spaced items on mixed lists, especially during massed presentations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overshadowing between landmarks on the touchscreen and in arena with pigeons.

The role of generalization decrement in spatial overshadowing was evaluated using a landmark-based spatial search task in both a touchscreen preparation (Experiment 1a) and in an Automated Remote Environmental Navigation Apparatus (ARENA, Experiment 1b). A landmark appeared as a colored circle among a row of eight (touchscreen) or six (ARENA) potential locations. On overshadowing trials, Landmark X was located two positions away from a hidden goal, while another landmark, A, was in the position between X and the goal. On control trials, Landmark Y was positioned two locations away from the goal but without a closer landmark. All subjects were then tested with separate trials of A, X, Y, and BY. Testing revealed poor spatial control by X relative to A and Y, thereby replicating the spatial overshadowing effect. Spatial control by Y was similar when tested in compound with novel landmark (BY) and on trials of Y alone. Thus, overshadowing in a small-scale environment does not appear to be due to a process of generalization decrement between training and testing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Overshadowing and the outcome-alone exposure effect counteract each other.

Three conditioned lever-press suppression experiments with rats investigated the interaction between overshadowing and outcome-alone exposure effects. Experiment 1 found in first-order conditioning that combined overshadowing and outcome-preexposure treatments attenuate the response deficit produced by either treatment alone. Experiments 2 and 3 investigated the interaction between overshadowing and outcome pre- and postexposure effects in sensory preconditioning, varying retention intervals to engage recency and primacy effects with respect to treatment order. Contrary to when a solitary cue is conditioned, responding to a cue conditioned in compound appeared positively correlated with the context's associative status. These findings suggested that some of the basic laws of learning applicable to cues conditioned alone do not similarly apply to a component of a compound cue. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Proactive interference between cues trained with a common outcome in first-order Pavlovian conditioning.

The nature of interference between cues (X, A) trained apart with a common outcome (O; an unconditioned stimulus) was explored by assessing proactive interference in first-order Pavlovian conditioning (i.e., A-O, X-O, resulting in attenuated responding to X). Three lick-suppression studies were conducted with water-deprived rats. Posttraining extinction of the interfering cue (A) attenuated proactive interference (Experiment 1), which mirrors the observation that extinction of the competing cue can reduce competition between cues trained together (e.g., recovery from overshadowing). Proactive interference was also attenuated with manipulations known to attenuate interference between outcomes trained apart (e.g., counterconditioning), namely reminder cues (Experiment 2) and renewal (Experiment 3). The findings suggest that similar processes underlie interference between cues trained apart, between cues trained together, and between outcomes trained apart. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detrimental Influence of Contextual Change on Spacing Effects in Free Recall.

Two experiments were conducted to determine the mechanism underlying the spacing effect in free-recall tasks. Participants were required to study a list containing once-presented words as well as massed and spaced repetitions. In both experiments, presentation background at repetition was manipulated. The results of Experiment 1 demonstrated that free recall was higher for massed items repeated in a different context than for massed items repeated in the same context, whereas free recall for spaced items was higher when repeated in the same context. Furthermore, a spacing effect was shown for words repeated in the same context, whereas an attenuated spacing effect was revealed for words repeated in a different context. These findings were replicated in Experiment 2 under a different presentation background manipulation. Both experiments seem to be most consistent with a model that combines the contextual variability and the study-phase retrieval mechanism to account for the spacing effect in free-recall tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overexpectation and trial massing.

Three experiments were conducted to examine the interaction of overexpectation treatment and trial massing using a Pavlovian fear conditioning procedure with rats. In first-order conditioning, Experiment 1 found the overexpectation effect (i.e., decreased conditioned responding to a cue after compound training when the elements were previously reinforced), the trial spacing effect (i.e., decreased responding to a cue when reinforced trials are massed), and a counteraction between overexpectation treatment and trial massing (i.e., an alleviation of the decrement in responding seen with overexpectation treatment or trial massing alone when the two treatments are conjointly administered). Experiment 2 replicated Experiment 1 with the critical treatments embedded within a sensory preconditioning preparation. The overexpectation effect, the trial spacing effect, and the mutual counteraction of overexpectation treatment and trial massing all proved significant. In Experiment 3, either the nontarget conditioned stimulus of overexpectation treatment or the excitatory context resulting from trial massing was extinguished. Results are best explained by the extended comparator hypothesis (J. C. Denniston, H. I. Savastano, & R. R. Miller, 2001). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cues trained apart compete for behavioral control in rats: Convergence with the associative interference literature.

Contemporary theories of associative learning require cues be trained in compound for cue competition (interference) to occur. That is, Cues A and X should compete for behavioral control only if training consists of AX-outcome (O) trials and not if each cue is separately paired with O (i.e., X–O and A–O). Research with humans challenges this view by showing that A–O trials interpolated between training and testing of a X–O association impair responding to X (i.e., retroactive interference). In six conditioned suppression studies with rats, the authors demonstrate that two cues trained apart can each interfere with the potential of the other to predict the outcome. The authors conclude that this type of interference (a) reflects a failure to retrieve the target association due to priming at test of the interfering association and (b) is attenuated if the outcome is of high biological significance. These findings parallel previous reports in verbal learning research and suggest that a similar associative structure underlies some types of associations in nonverbal subjects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Counterconditioning of an overshadowed cue attenuates overshadowing.

In 3 Pavlovian conditioned lick-suppression experiments, rats received overshadowing treatment with a footshock unconditioned stimulus such that Conditioned Stimulus (CS) A overshadowed CS X. Subjects that subsequently received CS X paired with an established signal for saccharin (CS B) exhibited less overshadowing of the X–footshock association than subjects that did not receive the X–B pairings (Experiment 1). Experiment 2 replicated this effect and controlled for some additional alternative accounts of the phenomenon. In Experiment 3, this recovery from overshadowing produced by counterconditioning CS X was attenuated if CS B was massively extinguished prior to counterconditioning. These results are more compatible with models of cue competition that emphasize differences in the expression of associations than those that emphasize differences in associative acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characteristics of associative learning in younger and older adults: Evidence from an episodic priming paradigm.

Two experiments investigated age differences in the encoding of associative information during a speeded naming task. In both experiments, semantically unrelated prime-target word pairs were presented 4 times, in either massed or spaced fashion, during the learning phase. An immediate or delayed test trial was presented following the fourth presentation. In Experiment 1, participants named both the primes and the targets. Younger and older adults showed similar benefits when naming targets that were part of a consistent prime-target pairing compared with targets presented with different primes at each presentation. In Experiment 2, participants named only the target word. Younger adults showed a benefit for consistently paired words, whereas older adults showed no benefit for consistently paired words. The results of the test trials showed a greater benefit for massed repeated words than for spaced repeated words at the immediate test and a reversed pattern at the delayed test. This spacing by test delay interaction was evident in response latency in Experiment 1 and in cued recall performance in Experiment 2. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trial spacing and trial distribution effects in Pavlovian conditioning: Contributions of a comparator mechanism.

Two experiments, involving a total of 144 rats, investigated a potential basis for trial spacing and trial distribution effects. In Exp 1, a CS (e.g., CS A) was trained with either massed (e.g., A?→?A?→?A) or spaced (e.g., A A A) trials. When trials were massed, brief exposure to the training context (a condition typical of massed training) impaired responding, whereas more extensive exposure to the context during or after training reduced this apparent massed trials deficit. In Exp 2, different CSs were trained in either a massed (e.g., A?→?A?→?A?→?B?→?B?→?B?→?C?→?C?→?C) or a distributed (e.g., A?→?B?→?C?→?A?→?B?→?C, etc.) manner. Trials massed in this sense resulted in impaired responding to the CS, and this impairment was attenuated by posttraining extinction of the context cues. Thus, trial distribution and apparent trial spacing effects were, at least in part, reversible deficits in performance rather than failures of learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of paraphrased repetitions on the spacing effect.

In two experiments, we examined the "spacing" effect in students' memory for paragraphs and brief lectures. In the first experiment, students who read massed verbatim repetitions of paragraphs recalled less of the content than did students who read verbatim repetitions spaced across time. In addition, students who read paraphrased versions of the paragraphs in massed repetitions recalled as much as did students who read the paragraphs in the spaced conditions. For Experiment 2, we used a brief lecture as the to-be-learned material and replicated the results of Experiment 1. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Outcome Additivity and Outcome Maximality Influence Cue Competition in Human Causal Learning.

Recent research suggests that outcome additivity pretraining modulates blocking in human causal learning. However, the existing evidence confounds outcome additivity and outcome maximality. Here the authors present evidence for the influence of presenting information about outcome maximality (Experiment 1) and outcome additivity (Experiment 2) on subsequent forward blocking. The results of Experiment 3 confirm that, with outcome maximality controlled, outcome additivity affects backward blocking but not release from overshadowing. Finally, the results of Experiment 4 demonstrate that information about outcome additivity has a similar effect on forward blocking if presented after the blocking training instead of before. The results are compatible with the idea that blocking results from inferential processes at the time of testing and not from a failure to acquire associative strength during training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Potentiation and overshadowing in Pavlovian fear conditioning.

The present experiments addressed a fundamental discrepancy in the Pavlovian conditioning literature concerning responding to a target cue following compound reinforced training with another cue of higher salience. Experiment 1 identified one determinant of whether the target cue will be overshadowed or potentiated by the more salient cue, namely contiguity between compound CS termination and US presentation. Overshadowing and potentiation were observed with delay and trace procedures, respectively. Experiments 2 and 3 contrasted elemental and configural explanations of potentiation. Both experiments supported a configural account. Experiments 3 and 4, by manipulating prior learning experiences to bias subjects to encode the same compound elementally or configurally, demonstrated decreased potentiation and overshadowing, respectively. Overall, these experiments demonstrate potentiation with nontaste stimuli and identify one variable that determines whether overshadowing or potentiation will occur. Moreover, they show that prior experiences can determine how a compound is encoded and are compatible with the idea of flexible encoding as a principle of information processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)