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)     

Recency-to-primacy shift in cue competition.

Three experiments were conducted using a lick-suppression preparation with rats to determine whether temporal and physical context shifts modulate the effectiveness of 2 sequentially trained blocking stimuli. Experiment 1 ascertained that it is possible to obtain blocking by conditioning rats to react to a target cue using 2 different blocking cues, each trained with a single-phase blocking paradigm. Experiment 2 showed that the more recently trained blocking stimulus was more effective (i.e., showed a recency effect) when testing was conducted immediately after training, but a long retention interval attenuated blocking by the most recently trained blocking stimulus and increased blocking by the initially trained blocking stimulus (i.e., a recency-to-primacy shift). This shift from recency to primacy affected in Experiment 2 by varying the retention interval was replicated in Experiment 3 by changing the physical context between training and testing. Taken together, the results indicate that the effectiveness of sequentially trained competing stimuli follows the same recency-to-primacy shift rule that is seen in traditional interference phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory list memory and interference processes in monkeys.

Memory of 2 rhesus monkeys (Macaca mulatta) was tested in a serial probe recognition task with lists of 4 natural or environmental sounds, different retention intervals, and different manipulations of interference. At short retention intervals, increasing the separation of list items reduced the primacy effect and produced a recency effect. Similar results were shown by increasing interference across lists through item repetitions or making the first 2 list items high-interference items. These results indicated that decreasing first-item performance reduced proactive interference on memory of the last list items. At long (20 sec) retention intervals, making the last list items of high interference reduced the recency effect, reduced retroactive interference, and produced a primacy effect. Taken together, interference plays a role in determining the primacy and recency effects of the serial-position function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Drug exposure and the acquisition and retention of a conditioned taste aversion

Two experiments examined the effects of preexposure and postexposure to a drug on the acquisition and retention of a conditioned taste aversion induced by that drug. Experiment 1 demonstrated that although drug preexposure attenuated a subsequent conditioned aversion, repeated taste-drug pairings reversed the initial attenuation effect and resulted in nearly complete avoidance of consumption. Experiment 2, however, demonstrated that drug postexposure did not alter a previously established conditioned aversion, although the postexposure experiences were effective in attenuating a conditioned aversion to a second novel solution. It was suggested that conditioned aversions are mediated by ACTH and that preexposure to a drug results in tolerance to that drug, yielding a smaller ACTH response and thereby a weaker aversion.     

Response bias in visual serial order memory

The recency-to-primacy shift represents a major challenge for all theories that attempt to explain the effects of serial order on memory. At short retention intervals, strong recency and no primacy effects occur, but as the retention interval increases, recency is attenuated and primacy increases. In 2 experiments, 24 participants were presented with sets of 4 unfamiliar faces and were asked to state the serial position of a probe face after 0 or 10 s. The predicted recency-to-primacy shift was obtained with accuracy responses. However, the distribution of responses also showed that there was a change in response bias with retention interval. When this was corrected for, the recency-to-primacy shift was eliminated. Response bias is suggested as the underlying cause of the recency-to-primacy shift in this task.     

A recency-based account of the primacy effect in free recall.

Seven experiments investigated the role of rehearsal in free recall to determine whether accounts of recency effects based on the ratio rule could be extended to provide an account of primacy effects based on the number, distribution, and recency of the rehearsals of the study items. Primacy items were rehearsed more often and further toward the end of the list than middle items, particularly with a slow presentation rate (Experiment 1) and with high-frequency words (Experiment 2). Recency, but not primacy, was reduced by a filled delay (Experiment 3), although significant recency survived a filled retention interval when a fixed-rehearsal strategy was used (Experiment 4). Experimenter-presented schedules of rehearsals resulted in similar serial position curves to those observed with participant generated rehearsals (Experiment 5) and were used to confirm the main findings in Experiments 6 and 7. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The shift from recency to primacy with increasing delay.

Five experiments examined the recency–primacy shift in which memory for early list items improves and memory for later items becomes worse as the delay between study and test increases. Experiment 1 replicated the shift in a recognition task in which the physical form of the study and test items differed, ruling out an explanation that invokes visual memory. Experiment 2 observed the change when only 1 serial position was tested, eliminating an explanation based on changing strategies or proactive interference. Experiment 3 showed a similar change from recency to primacy when the to-be-remembered stimuli were auditory. Experiments 4 and 5 demonstrated that the same recency–primacy trade-off occurs for words in a sentence. Although it is possible to offer piecemeal explanations for each experiment, the dimensional distinctiveness model accounts for the results in each of the 5 experiments in exactly the same way. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned irrelevance exceeds the sum of CS-preexposure and US-preexposure deficits.

Barpress suppression by water-deprived rats was used to examine the retarded emergence of excitatory responding when a tone conditioned stimulus (CS) and a shock unconditioned stimulus (US) were paired following uncorrelated exposure to the CS and US. Experiment 1{a} established parameters whereby the retardation resulting from preconditioning CS-alone presentations (latent inhibition) was eliminated by presenting unpredictable, nontarget neutral stimuli (clicks) after each CS during the preconditioning phase, a treatment thought to maintain attention to the CS. Experiment 1{b} established parameters whereby the retardation resulting from preconditioning US-alone presentations was eliminated by preceding each US with a 2nd nontarget cue (a light) during the preconditioning phase, which presumably reduced acquisition of context–US associations. In Experiment 1{c}, the techniques to attenuate CS-preexposure and US-preexposure effects were imposed on a random schedule of CS and US presentations. Although this procedure reduced subsequent retardation, an appreciable response deficit remained. In Experiment 2 a context shift between CS-alone or US-alone presentations and subsequent CS–US pairings eliminated retardation, but retardation arising from uncorrelated exposures to the CS and US, albeit significantly reduced, transferred between contexts. These results suggest that the deficit resulting from preconditioning, uncorrelated exposures to the CS and US is composed of a CS preexposure effect, a US preexposure effect, and learned irrelevance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial position effects and duration of memory for nonspatial stimuli in rats.

Recognition memory for lists of nonspatial items was tested in rats using a nonmatching-to-sample task. The recency effect at short retention intervals disappeared as the interval increased, but primacy did not develop although responding was still above chance up to 2 hr after 10-s sample times. Neither proactive nor retroactive interference was apparent. Rats transferred the nonmatching-to-sample rule to completely novel stimuli. The study failed to replicate the prominent U-shaped serial position curve found in a similar study by P. Reed, T. Chih-Ta, J. P. Aggleton, and J. N. P. Rawlins (1991), for which E. A. Gaffan and D. Gaffan (1992) had found the data less variable than expected. Evidence of primacy in this procedure remains insubstantial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Combined effect of context change and retention interval on interference in causality judgments.

Four experiments studied the effects of context change and retention interval on retroactive interference in human causal learning. Experiment 1 found evidence of retroactive interference. Experiment 2 found that either a 48-hr retention interval or a change in the context after the interference treatment decreased retroactive interference. An interaction between context change and retention interval effects was also found, eclipsing the context change effect after the 48-hr retention interval. Experiments 3 and 4 found additivity between context change and retention interval effects when participants were reminded of the difference between physical contexts before the test, independently of whether the context change involved a return to the original acquisition context. These results add to the evidence suggesting that spontaneous forgetting is caused by a change in either the physical or the temporal contexts when information is acquired. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

List item memory in rats: Effects of delay and delay task.

The Serial Position Effect (SPE) was studied in rats using 2 manipulations analogous to those that have been shown to decrease the recency effect but leave the primary effect intact in human Ss. In Part 1, delays (5 sec to 60 sec) were imposed between exposure to a sequence of arms presented in 12-arm radial maze and a subsequent test phase. In Part 2, the effect of free access to food in a short (10-sec) delay was examined. The results from Parts 1 and 2 showed the primacy and recency effects were differentially sensitive to the delay and events within it. In particular the recency effect was found to be more sensitive to disruption from these sources. The present demonstration of a reduction in recency with procedures analgous to those used with humans extends the evidence, suggesting that the SPE obtained in rats and humans is a similar phenomenon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessments of Changes in the Effective Salience of Stimulus Elements as a Result of Stimulus Preexposure.

Rats received exposure to 3 flavor compounds, AX and BX, presented in alternation, and CX, presented on a separate block of trials. The hypothesis that this treatment would leave B effectively more salient than C was tested in 3 ways. Experiment 1 showed that the unconditioned response evoked by B was stronger than that evoked by C. Experiment 2 showed that B was more effective than C when used as a reinforcer in a sensory preconditioning procedure. Experiment 3 showed that B was learned about more readily than C as a conditioned stimulus in flavor aversion conditioning. Alternating preexposure to 2 similar stimuli may protect their distinctive features from the loss of salience normally produced by nonreinforced exposure to a stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spontaneous Recovery From Forward and Backward Blocking.

This article demonstrates and analyzes spontaneous recovery of stimulus control following both forward and backward blocking in a conditioned suppression preparation with rats. Experiment 1 found, in first-order conditioning, robust forward blocking and an attenuation of it following a retention interval. Experiment 2 showed, in sensory preconditioning, recovery of responding following both forward and backward blocking. Also, the results of this experiment indicated that response recovery to the blocked stimulus cannot be explained by an impaired status of the blocking stimulus after a retention interval. Experiment 3, also in sensory preconditioning, suggested that spontaneous recovery following both forward and backward blocking in Experiment 2 was due to impaired associative activation of the blocking stimulus' representation during testing with the blocked stimulus. Although no contemporary model of associative learning can explain these results, a modification of R. R. Miller and L. D. Matzel's (1988) comparator hypothesis is proposed to do so. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dogmatism and belief formation: Output interference in the processing of supporting and contradictory cognitions.

The role of reason generation in dogmatic thinking was examined by means of cognitive response analysis. In Experiment 1, dogmatism was associated with greater confidence in judgments as a result of postjudgment generation of more supporting and less contradictory evidence. Experiment 2 produced similar results for confidence judgments with prejudgment reason generation, except that no difference in supporting evidence was found as a function of dogmatism. Experiment 3 showed that dogmatism was associated with greater output interference in reason generation, leading to greater primacy effects in likelihood judgments. A delay between generation of reasons reduced output interference effects, but only for those low in dogmatism who showed a recency effect. The results were interpreted in terms of cognitive mechanisms in dogmatic thinking after artifactual and motivation explanations had been ruled out. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Primacy versus recency in persuasion as a function of the timing of arguments and measures.

In an after-only design 4 independent variables were manipulated to test Miller and Campbell's theory of primacy vs. recency in persuasion: time between communications (none, 2 days, 1 week, or 2 weeks), time between the 2nd communication and the measures of opinion and retention (none, 2 days, or 1 week), order of communications (pro-con or con-pro), and order of measures (opinion-recall or recall-opinion). There were 2 dependent variables: opinion (measured on a rating scale) and retention (measured through recall). Confirming Miller and Campbell, the longer the time interval between 2 communications the greater the recency effect in both opinion and recall immediately after the 2nd communication; and the longer the time elapsed from the 2nd communication until measurement the less the recency effect. Contrary to Miller and Campbell's prediction, delayed measurement did not tend to produce primacy in the case of the groups in which the 2nd communication followed immediately upon the 1st. The theoretically predicted shape of the recency function over time was only roughly supported. A correlational analysis of the relation between opinion and retention called into question the assumption that opinion is a direct function of retention of message content. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual list memory in capuchin monkeys (Cebus apella).

Memory of 3 capuchin monkeys, Cebus apella, was tested with lists of 4 travel-slide pictures and different retention intervals. They touched different areas of a video monitor to indicate whether a test picture was in a list. At short retention intervals (0 s, 1 s, 2 s), memory was good for the last list items (recency effect). At a 10-s retention interval, memory improved for 1st list items (primacy effect). At long retention intervals (20 s and 30 s), primacy effects were strong and recency effects had dissipated. The pattern of retention-interval changes was similar to rhesus monkeys, humans, and pigeons. The time course of recency dissipation was similar to rhesus monkeys. The capuchin's superior tool-use ability was discussed in relation to whether it reflects a superior general cognitive ability, such as memory. In terms of visual memory, capuchin monkeys were not shown to be superior to rhesus monkeys. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contributions to the functional analysis of single-trial free recall.

An extensive body of research generated by the now outmoded dual store model has produced a set of functional principles of single-trial free recall. One principle, termed the ratio rule, describes the properties of the recency effect, while several others based upon laws of rehearsal have been advanced to account for the primacy effect. These principles, which may eventually establish the foundation for a more comprehensive theory of list memory, were tested in three experiments. The first two experiments showed that when rehearsal is eliminated (Experiment 1) or equated (Experiment 2), reliable primacy and recency effects are obtained. The third experiment demonstrated that the effectiveness of rehearsal during list presentation declines monotonically as a function of serial position. These results contrast with the prevailing functional account of both primacy and recency effects and suggest several new lines of inquiry into the subject. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of item-specific information for the serial position curve in free recall.

The serial position curve in free recall of a list of action phrases differs depending on whether the phrases were memorized by listening/reading (verbal task; VT) or by additionally enacting the denoted actions (subject-performed task; SPT). In VTs there is a clear primacy effect and a short recency effect. In SPTs there is no primacy effect but an extended recency effect. H. D. Zimmer, T. Helstrup, and J. Engelkamp (2000) assumed that SPTs provide excellent item-specific information, which leads to an automatic pop-out of the items presented last. In the present study, the authors assumed that good item-specific encoding generally enhances the recency effect and that it hinders rehearsal processes and thereby reduces the primacy effect. This assumption was confirmed. An item-specific orienting task leads to parallel serial position curves in VTs and SPTs with no primacy effect but a clear recency effect. Moreover, the same serial position effects were shown with nouns as learning material. An item-specific orienting task changes the classical U-shaped serial position curve with verbal material and leads to the disappearance of the primacy and the enhancement of the recency effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preexposure effects in the spatial domain: Dissociation between latent inhibition and perceptual learning.

In 4 experiments, rats were given intermixed or blocked preexposure to an array of landmarks that subsequently defined the location of a hidden goal in a Morris pool task. Previous research has shown that intermixed preexposure to pairs of adjacent landmarks retards learning whereas preexposure to individual landmarks facilitates subsequent learning (J. Prados, V. D. Chamizo, & N. J. Mackintosh, 1999). Accordingly, in Experiment 1, intermixed and blocked preexposure to pairs of adjacent landmarks was found to retard learning. In Experiment 2, however, a scheduling effect was found: Rats given intermixed preexposure to the individual landmarks learned faster than rats given blocked or no preexposure. Experiment 3 showed that intermixed (but not blocked) preexposure to pairs of landmarks resulted in a facilitatory effect when preexposure and test were carried out in different contexts. Experiment 4 replicated within a single experiment the main results observed in Experiments 1 and 3. This pattern of results suggests that intermixed preexposure engages learning processes other than latent inhibition that facilitate subsequent learning of the navigation task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Accidental exposure of veterinary students to rabies

Accidental exposure to rabies occurred in more than 200 veterinary students at Texas A&M University from 1970 to 1977. Few of the animals to which the students were exposed had typical signs of rabies prior to the exposures. An accelerated preexposure rabies prophylaxis program coupled with retention of suspect tissues suitable for fluorescent antibody procedures has reduced the number of postexposure prophylaxis series.