The role of local context in autoshaping

Three experiments used an autoshaping procedure with pigeons to examine the effects of nonreinforced, nontarget stimuli (ITI-fillers) during the intertrial interval on responding to a reinforced target CS. Experiment 1 replicated a previous demonstration that an ITI-filler that occupied a substantial portion of the ITI attenuated responding to the target CS relative to a group trained with a similar ITI but lacking the ITI-filler. Experiment 2 found that the superiority of responding typically found with a long ITI relative to a short ITI, that is, the trial-spacing effect, can be reversed by imposing a filler stimulus during the ITI in the former condition. Experiment 3, using a within-subject design, found that when one background stimulus condition occupied a majority of the interreinforcement interval, pairings of one target CS with reinforcement that were embedded within this background condition, that is, a long duration local context occurred for this CS, yielded better performance that a second, reinforced, target CS paired with reinforcement in the shorter duration background condition. These results confirmed predictions derived from a local context view of cycle time. Comparator theories of classical conditioning require incorporation of this notion into their conceptualization of effective cycle time in order to explain the present findings.     

The dud-alternative effect in memory for associations: Putting confidence into local context

When participants are asked to provide confidence judgments for each provided alternative in a multiple-choice memory task, such judgments are inflated if the assessed alternatives are accompanied by an implausible (dud) alternative. This finding, termed the dud-alternative effect, has been recently documented in a memory setting with a lineup procedure (Charman, Wells, & Joy, Law & Human Behavior 35:479–500 2011). In the present study, we developed a novel paradigm to investigate the dud-alternative effect in memory. The paradigm utilizes a multiple-choice associative recognition task in which dud alternatives can be rejected on the basis of their unfamiliarity. In two experiments, we demonstrated a reliable dud-alternative effect with our novel procedure. The results demonstrated that the dud-alternative effect in episodic memory is not limited to tasks based on perceptual factors, but is a general phenomenon concerning confidence judgments.     

Differential conditioning of the rabbit's nictitating membrane response to serial compound stimuli

Three experiments were conducted to determine the time course and contents of CS representations through an examination of differential conditioning of the rabbit's nictitating membrane response to two serial compounds. One compound (A-X+) was always paired with the unconditioned stimulus, and the other (B-X-) was always presented alone. All three experiments entailed manipulation of the interstimulus interval between the initial distinctive element of each compound (A and B) and the second, shared element (X). The joint results revealed that (a) conditioned response acquisition to the initial elements depended on the presence of X in the A-X+ compound; (b) differentiation between A and B appeared across interstimulus intervals up to 4,600 ms; and (c) conditional control over responding following A and B appeared at interstimulus intervals of at least 4,600 ms and perhaps up to 12,600 ms. The results are discussed with respect to mechanisms of occasion setting, generalization, and configuration.     

Blocking of conditioned suppression: role of the first compound trial.

Four experiments, all employing the conditioned suppression of licking in thirsty rats, examined the extent to which reinforcement of one component, A, of a compound conditioned stimulus, AB, would "block" conditioning to the other element, B, on the first compound trial. Suppression to B was unaffected by prior reinforcement of A; that is, no evidence of blocking was obtained. If additional reinforced trials were given to the AB compound, further conditioning to B was blocked by prior reinforcement of A. Thus blocking appeared to take at least one trial to develop. These results suggest that blocking is not due to any competition between stimuli for association with reinforcement, but is a consequence of the animals' ignoring the added element once they have learned that it is redundant.     

Blocking acquisition of the rabbit's nictitating membrane response to serial conditioned stimuli

Three experiments demonstrated that prior training with one stimulus (CS1) would block acquisition of the rabbit's nictitating membrane response (NMR) to another stimulus (CS2) which was more contiguous to the US during serial compound training (CS1-CS2-US). Specifically, the CS1-US interval was 800 msec, which produces only a modest rate of CR acquisition, while the CS2-US interval was 400 msec, which is an optimal value for the NMR preparation. Experiment 1 demonstrated blocking when CS1 overlapped CS2, and Experiment 3 demonstrated blocking when CS1 and CS2 were presented in a strictly sequential fashion. Experiment 2 showed that the magnitude of blocking in the serial compound was comparable to that obtained in a simultaneous compound in which both the CS1-US and CS2-US intervals were 800 msec, thus making CS2 less contiguous with the US than in the serial compound. Moreover, the level of responding to CS2 in all serial compound groups (blocking and control) was lower than in the simultaneous compound groups. The present findings provide further evidence that the associative consequences of CS-US contiguity can be highly attenuated by processes of attention or competition for associative strength.     

Examining the role of context variability in memory for items and associations

What properties of a word make it easy or difficult to remember? Word frequency and context variability are separate, closely related word properties that have disparate influences on memorability. The influence of word frequency changes depending on the memory task, with high-frequency words tending to be recalled better and low-frequency words to be recognized better. Conversely, low-context-variability words tend to be remembered better across tasks. One proposed explanation for the low-variability advantage is that low-variability words are easier to associate with the experimental context, given that they are associated with fewer extra-experimental contexts. On the basis of this explanation, it has been suggested that the formation of interitem associations during encoding should interfere with the formation of item-to-context associations, attenuating the low-variability advantage. Across experiments, we tested whether focusing on interitem associations disrupted the low-variability advantage, by manipulating encoding tasks, test expectancy, final test condition, word frequency, and context variability. Focusing on interitem associations did not harm performance for low-variability words. Words low in both frequency and variability were recognized better, but word pairs composed of high-frequency, low-variability words were recognized better in associative recognition. On the basis of the data, we suggest that focusing on interitem associations does not come at the expense of item-to-context associations. Moreover, the data further support the idea that frequency and variability are distinct properties.     

Blocking but not conditioned inhibition results when an added stimulus is reinforced in compound with multiple pretrained stimuli

Conditioned barpress suppression by rats was used to explore the associative status of an initially neutral stimulus that was reinforced in simultaneous compound with two independently pretrained conditioned excitors. In contrast to the Rescorla-Wagner model, which predicts that the target stimulus (X) will be inhibitory following such A+/B+/ABX+ training, the present study found no evidence that X acquired inhibitory associative strength. Rather, the pretrained stimuli merely served to block conditioned excitatory responding to the target stimulus.     

The role of temporal context and expectancy in resource allocation to and perception of rapid serial events

The perception of target events presented in a rapid stream of non-targets is impaired for early target positions, but then gradually improves, a phenomenon known as attentional awakening. This phenomenon has been associated with better resource allocation. It is unclear though whether improved resource allocation and attentional awakening are a consequence of the temporal context, that is, the position of the target event in the stimulus stream, or are due to a simple expectancy or foreperiod effect. Expectancy is an alternative explanation of attentional awakening because it depends on the a posteriori probabilities, which will increase with target position when all target positions are equally likely. To differentiate between the expectancy and the temporal context account the a priori (objective) probability of target position was defined such that the a posteriori probability would be high for early and late, and low for intermediate target positions. EEG was collected and the P3 ERP evoked by target events was derived as an indicator of resource allocation. A robust attentional awakening effect was observed. The relationships between measures of performance and P3 amplitude, and respectively target position, a priori, and a posteriori probability were analyzed. Results showed that in contrast to target position, a posteriori probability had little impact on performance and did not moderate the association between P3 amplitude and performance. Results also indicated that in spite of the evident role of target position on resource allocation and the perception of target events in rapid stimulus streams, target position is likely not the only variable these are affected by. Nevertheless, the findings of the present study suggest that whereas the temporal context of a rapid serial event is a key player for resource allocation to and perception of the event, expectancy seems of very little consequence.     

Auditory–Visual stimuli: Effects on derived relations with compound stimuli

This research explored the effect of teaching conditional discriminations with three procedures on the derivation of 36 stimuli relations (derived relations). The stimuli used consisted of three characteristics musical instruments, along with the corresponding picture. In the first experiment six university students were trained with simple stimuli and tested with compound auditory–visual samples; therefore, a one‐to‐many structure was used. In the second experiment, auditory stimuli were replaced by visual stimuli, for the samples used, for new students. A third experiment was implemented with an extra phase of training with compound stimuli for six new students. The structure of the experiments was: pretests (Xbcd–A; Xacd–B; Xabd–C; Xabc–D), training (A–B; A–C; A–D), and posttests (same as pretests). The difference between these conditions was the kind of stimuli used and a new phase of teaching used in condition 3: (Xbcd–A). The results indicate that training with simple stimuli on discriminations that include stimuli that are easy to discriminate from each other (words and sounds) is a sufficient condition for good posttest performance. However, when comparisons are made difficult (words only), participants show better performance on new tests if they have a learning history with compound stimuli.     

Blocking of inhibitory conditioning within a serial conditioned stimulus-conditioned inhibitor compound: Maintenance of acquired behavior without an unconditioned stimulus

Well-trained classically conditioned stimuli, presented unreinforced, were protected from extinction when they were followed by a signal of the omission of the reinforcer (conditioned inhibitor Konorskian type) in eight cats. An aversive classical conditioning paradigm with shock as the reinforcer was used. Of several behavioral (leg flexion, vocalization) and organismic arousal (heart rate, respiration rate, respiration amplitude) measures of conditioned responses, the respiration amplitude changes were found to be most informative for the continuous assessment of elicited arousal of low and medium intensity. In all subjects conditioned stimuli presented during extinction in serial compound with the conditioned inhibitor elicited larger responses than did conditioned stimuli presented alone during extinction. The mechanism of protection from extinction in a paradigm in which the elicitor of learned behavior occurs prior to the conditioned inhibitor provides the organism with the mechanism for the maintenance of learned behavior in the absence of a reinforcer.     

Incidental formation of episodic associations: The importance of sentential context

The influence of relevant semantic context on the incidental formation of episodic associations between words was probed in two experiments. In Experiment 1, we examined the influence of associations formed incidentally between unrelated words presented either in isolation or embedded in a sentential context on subsequent explicit paired-associate leaning tested by cued recall. The results of Experiment 1 showed that the cued-recall rate of words studied in sentential context was higher than that of words co-occurring in isolated pairs. A subsequent single-items recognition test showed equal item memory for words studied in sentences than for words studied in isolated pairs, suggesting that the sentential context effect in cued recall indeed reflected stronger associations between paired words rather than better memory for single words. In Experiment 2, we ruled out memory for the entire sentence as an alternative explanation for the results of Experiment 1. We suggest two possible mechanisms to account for this advantage: First, pairs embedded in a sentence undergo semantic elaboration that might lead to the incidental formation of an association between them. Second, words embedded in a sentence enjoy the conjoint activation of compatible semantic features, a fact that may also facilitate the formation of an episodic association between them. The implications of these results for computational models using word representations based on co-occurrence data are discussed.     

The eye blink as a time-locked response: implications for serial and second-order conditioning

A series of experiments were conducted to determine what factors control responding to the first element of a two-element serial compound in rabbit eyelid conditioning. An examination of response topography indicated that the eye-blink CR is rigidly timed to occur when the US is expected. This response-system characteristic prevents the occurrence of a CR during the first element of a serial compound or during the second-order CS in second-order conditioning. The comparison of a serial gap procedure with conventional serial and trace conditioning procedures suggested that the associative strength of the first element of a serial CS is not strongly influenced by either a second-order conditioning process or by the variable-reinforcement principle.     

Control of matching by differential outcome expectancies in the absence of differential sample-outcome associations: a serial compound view

In this study, pigeons learned 2 separate one-to-many conditional discriminations in which they matched form samples to line and hue comparisons. Correct choices within each comparison dimension yielded differential (food vs. no-food) outcomes that were not predictable from the samples alone. At asymptote, latency to make a correct choice was shorter when food was the contingent outcome than when no food was the outcome. More important, when the samples from each task were subsequently exchanged, comparison choice varied systematically as a function of the sample and the set of new comparison alternatives that followed them. Together, these results indicate that choices were cued by differential outcome expectancies arising from serial compounds consisting of each sample and the dimensional characteristics of the comparisons.     

The roles of outcome and position associations in animal serial learning

Evidence that outcome associations, position associations, and response patterns each contribute to performance in animal serial learning came from two experiments in which three-trial series of rewarded and not-rewarded trials were examined. Response patterns were disrupted in Experiment 1 by placing animals directly in the goal on selected trials, a procedure that reduced (favoring outcome associations) but did not eliminate (favoring position associations) serial behavior. Series constructed to make outcome associations impossible (Experiment 2) produced serial behavior that indicated salient position associations can serve as phrasing cues to chunk the position information contained in the series.     

Rapid serial naming: relations between different stimuli and neuropsychological factors

We report two studies on rapid serial naming (RSN). Study 1 addressed the relations among RSN tasks comprising different stimuli. Separate components for RSN of alphanumeric and non-alphanumeric stimuli, as well as for tasks in which the stimuli alternated between categories were identified. In Study 2, phonological skills, processing speed, motor dexterity, and verbal fluency were found to explain RSN performance. The studies indicate: (1) that RSN tasks vary in their properties according to the stimuli used and according to the way the tasks are arranged, and (2) that RSN tasks are multi-componented.     

The role of fear-relevant stimuli in visual search: a comparison of phylogenetic and ontogenetic stimuli

It has been argued that phylogenetic fear-relevant stimuli elicit preattentive capture of attention. To distinguish between fear relevance and time of appearance in evolutionary history, the authors compare phylogenetic and ontogenetic fear-relevant and fear-irrelevant stimuli in a visual search task. The authors found no evidence for a special role of phylogenetic fear-relevant stimuli; it seems that fear relevance in general is more important than is the evolutionary age. The pattern of results indicates that attention toward threatening stimuli is mainly affected by a late component that prolongs the disengagement of attention.     

Blocking by fixed and variable stimuli: Effects of stimulus distribution on blocking

An experiment with rats compared the ability of fixed and variable duration cues to produce blocking. Rats in group B (Blocking) were trained that both fixed- (F) and variable- (V) duration cues would be followed by food delivery. In a subsequent training stage F and V continued to be reinforced, but F was accompanied by X, and V by Y. In the test phase responding to X and Y was examined. Control group O (Overshadowing) received identical treatment, except that F and V were nonreinforced in the first training stage. In group B there was evidence for blocking, but only of X, which had been conditioned in compound with the fixed-duration F; there was no evidence for blocking of Y, which had been conditioned in compound with the variable-duration V. It is suggested that this result may occur because fixed cues reach a higher, more stable asymptote of associative strength than do their variable equivalents.