The role of the hippocampus in memory for the temporal order of a sequence of odors.

Memory for the temporal order of a sequence of odors was assessed in rats. A sequence of 5 odors mixed in sand was presented in digging cups, 1 at a time, to each rat in a sequence that varied on each trial. A reward was buried in each cup. After the 5th odor, 2 of the previous 5 odors were presented simultaneously; to receive a reward, the rat had to choose the odor that occurred earliest in the sequence. Temporal separations of 1, 2, or 3 represented the number of odors that occurred between the 2 odors in the sequence. Once a preoperative criterion was reached, each rat received a hippocampal (HIP) or cortical control lesion and was retested on the task. On postoperative trials, the HIP group was impaired relative to controls. However, the HEP group could discriminate between the odors. The data suggest that the hippocampus is involved in separating sensory events in time so that 1 event can be remembered separately from another event. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The memory recall paradigm: Straightening out the historical record.

Traces the inadvertent distortion of historical detail committed by various authors in the dissemination of memory recall results from A. D. de Groot's (1946 [1965]) work with chess masters. The misrepresentation of these details not only has not been corrected but seems to be spreading. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oscillator-based memory for serial order.

A computational model of human memory for serial order is described (OSCillator-based Associative Recall [OSCAR]). In the model, successive list items become associated to successive states of a dynamic learning-context signal. Retrieval involves reinstatement of the learning context, successive states of which cue successive recalls. The model provides an integrated account of both item memory and order memory and allows the hierarchical representation of temporal order information. The model accounts for a wide range of serial order memory data, including differential item and order memory, transposition gradients, item similarity effects, the effects of item lag and separation in judgments of relative and absolute recency, probed serial recall data, distinctiveness effects, grouping effects at various temporal resolutions, longer term memory for serial order, list length effects, and the effects of vocabulary size on serial recall. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Item and order information in spatial memory.

14 male Holtzman albino rats were taught to perform order and item discriminations in an 8-arm radial maze. In Exp I, 2 groups of Ss learned different order discriminations with reward contingent on repeating or avoiding the most recently visited of 2 locations. Each trial began with a random order of 8 forced choices and ended with a choice between the 1st and 7th arms. Rate of learning depended on the compatibility of reward contingencies and preexperimental response biases. In Exp II, each trial began with a list of 7 forced choices and ended in a choice between either the 1st or 6th arm and the arm not presented; accuracy of performing these item discriminations depended on both serial position and the response tendencies acquired in Exp I. In Exp III, a 1-hr postlist delay impaired the order discrimination more than the item discrimination, and the effects of intertrial interval depended on previously acquired response biases. Results are discussed in terms of a 2-stage model that segregates a single memory process from decision/response processes. Item and order discriminations do not appear to be based on separate sources of information and do not appear to require fundamentally different memory processes. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Position and order information in recognition memory.

In three experiments we examined short-term recognition memory for order information. In each, a target string of letters was followed by a test string to which the subject responded "same" or "different." The test string either was identical to the target, or it included a transposition of a single pair of letters. Results were consistent in showing that the closer two transposed letters were to another in the target string, the poorer was the recognition of transposition. A probed recall procedure introduced in Experiment 3 required subjects to identify the serial position in the target string held by the probe letter. This procedure showed that memory for a letter's serial position was distributed over a number of serial positions and that the overlap of such positional uncertainty functions for individual pairs of adjacent items predicted recognition memory for transposition. Uncertainty about position of occurrence appears to determine order information, at least in part, and constitutes a neglected aspect of current theories of serial-position phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memories: True and false.

Supports K. S. Pope's (see record 83-37387) questioning of claims made by proponents of the false memory syndrome. The author suggests that the literature reviewed by Pope further indicates that the facility which with false memories may be produced is related to the distance between real experience and the imposed distortion. The relative malleability of memory is an important theoretical and practical issue, as is the use of memory retrieval in psychotherapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thought suppression in patients with bipolar disorder.

Suppression of negative thoughts has been observed under experimental conditions among patients with major depressive disorder (MDD) but has never been examined among patients with bipolar disorder (BD). Patients with BD (n = 36), patients with MDD (n = 20), and healthy controls (n = 20) completed a task that required unscrambling 6-word strings into 5-word sentences, leaving out 1 word. The extra word allowed the sentences to be completed in a negative, neutral, or “hyperpositive” (manic/goal-oriented) way. Participants completed the sentences under conditions of cognitive load (rehearsing a 6-digit number), reward (a bell tone), load and reward, or neither load nor reward. We hypothesized that patients with BD would engage in more active suppression of negative and hyperpositive thoughts than would controls, as revealed by their unscrambling more word strings into negative or hyperpositive sentences. Under conditions of load or reward and in the absence of either load or reward, patients with BD unscrambled more negative sentences than did controls. Under conditions of reward, patients with BD unscrambled more negative sentences than did patients with MDD. Patients with BD also reported more use of negative thought suppression than did controls. These group differences in negative biases were no longer significant when current mood states were controlled. Finally, the groups did not differ in the proportion of hyperpositive sentence completions in any condition. Thought suppression may provide a critical locus for psychological interventions in BD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term memory for serial order: the Start-End Model

Three solutions to the problem of serial order can be identified: chaining, ordinal and positional theories. Error patterns in serial recall from short-term memory fail to support chaining theories, yet provide unequivocal evidence for positional theories. In a new model of short-term memory, the Start-End Model (SEM), the positions of items in a sequence are coded relative to the start and end of that sequence. Simulations confirm SEM's ability to capture the main phenomena in serial recall, such as the effects of primacy, recency, list length, grouping, modality, redundant suffices, proactive interference, retention interval, and phonological similarity. Moreover, SEM is the first model to capture the complete pattern of errors, including transpositions, repetitions, omissions, intrusions, confusions, and, in particular, positional errors between groups and between trials. Unlike other positional models however, SEM predicts that positional errors will maintain relative rather than absolute position, in agreement with recent experiments (Henson, 1977).     

Scheduling processes in working memory: instructions control the order of memory search and mental arithmetic

Humans must often use working memory to execute processes one at a time because of its limited capacity. Two experiments tested where limits in access to working memory occur. Subjects searched a short-term memory set for one stimulus digit and performed mental arithmetic with another stimulus digit. In one experiment, they were told to carry out the mental arithmetic before the memory search and to make the arithmetic response first. In the other, they were instructed to perform the tasks in the opposite order. The overt responses were executed in the prescribed order. Moreover, the covert working memory processes were executed in the prescribed order, as revealed by a critical path network analysis of reaction times. Results are explained in terms of a double-bottleneck model in which central processes and responses are constrained to be carried out for one task at a time.     

von Restorff revisited: Isolation, generation, and memory for order.

The effects of isolation and generation on memory for order were investigated in 4 experiments. Exp 1 and 2 examined the effect of isolation on order retention. Previous investigations in this area have yielded equivocal results. Experiments 1 and 2 revealed that isolation enhances memory for order: Isolated items were repositioned more accurately than comparable items in control lists. Experiments 3 and 4 investigated the effect of generation on order retention. These experiments revealed that generation can enhance, disrupt, or have no effect on memory for order, depending on the relative number of generated items appearing within a list. Implications of these results for general theoretical accounts of isolation effects in memory are discussed. A simplified feature model (J. S. Nairne, see record 1990-27505-001) is shown to provide a general account of isolation effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Test sequence priming in recognition memory.

The authors examined priming within the test sequence in 3 recognition memory experiments. A probe primed its successor whenever both probes shared a feature with the same studied item (interjacent priming), indicating that the study item like the probe is central to the decision. Interjacent priming occurred even when the 2 probes did not themselves share any features: A lure that shared a single feature with a study item primed a lure that shared a different feature with the same study item. The experiments distinguished interjacent priming from other types of facilitation. Interjacent priming indicates that a study item that is like the probe is more relevant to the decision than other study items, contrary to global memory models. It also shows that negative decisions depend on contradiction, not insufficient familiarity, because lures, as well as targets, benefited. The data are discussed in terms of a recall check within a dual-process theory, but the authors prefer a single-process resonance model with separate decision mechanisms for yes and no responses (D. J. K. Mewhort & E. E. Johns, 2005). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The moderating effects of stimulus valence and arousal on memory suppression.

This study examined the separate and combined effects of stimulus valence and arousal on retrieval inhibition. Participants performed Anderson and Green's (2001) memory suppression task with stimuli varying across dimensions of valence and arousal. Memory was tested through free and cued recall as well as speeded recognition. Results showed that both stimulus valence and arousal influenced the extent to which participants successfully inhibited retrieval, but not in the ways anticipated. Specifically, the strongest inhibition effects were for highly arousing, pleasant words. In addition, unpleasant stimuli that were suppressed were better recalled during both cued and free-recall tasks than pleasant stimuli that were suppressed. Across all tests of memory performance, there were no significant differences between the experimental conditions for highly arousing, unpleasant words. The implications of these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intralist distractors and recall direction: Constraints on models of memory for serial order.

The serial-order version of the theory of distributed associative memory (TODAM; S. Lewandowsky and B. B. Murdock [see PA, Vol 76:14457]) predicts that disuption of forward serial recall should leave backward recall largely unaffected. This article reports 4 experiments in which the effects of an intralist distractor task were compared for forward and backward serial recall. Regardless of whether Ss could anticipate recall direction at study, the distractor task was found to disrupt forward but not backward recall. Although the existence of that dissociation had been predicted by TODAM, the theory was unable to provide a quantitative account of the data. Instead the authors provide a retrieval-based account within the framework of temporal distinctiveness theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhancing effects of similarity on long-term memory for order.

Four incidental learning experiments examined the effects of stimulus similarity on long-term memory for order. Although most current theories of order retention easily handle, and often predict, a disruption in order retention under conditions of high intralist similarity, the opposite result, an enhancing effect of similarity, presents a significant interpretive puzzle. All 4 of the present experiments demonstrate conditions in which phonological or categorical similarity significantly improves both absolute and relative long-term memory for sequential order. Tentative interpretations of these results are provided, on the basis of list discrimination arguments and the operation of study–phase reminding processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of item and order memory following parietal cortex lesions in the rat.

Rats with parietal cortex lesions were tested for both item and order memory for a list of spatial events in a probe recognition procedure. Rats with parietal cortex lesions were impaired for all events within the item memory task but had good memory for the early events within the order memory task. These data suggest a dissociation of function between item and order memory for parietal cortex damaged animals. In conjunction with previous findings with rats with medial prefrontal cortex lesions, these data suggest that item and order memory can be coded and represented independently. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Representation of order information: An analysis of grouping effects in short-term memory.

Exps I–IV tested the independence model, 2 hierarchical models, and the dependence model of matrix relationships with a probed recall procedure in which 91 undergraduates were presented with a grouped sequence of items and were then required to recall the position and group of 1 of the items. This technique provided information about how well Ss correctly recalled both the group and position, the group only, the position only, and neither the group nor the position of an item. Findings reveal that when the items in a group were letters, digits, or musical notes, the data conformed to a hierarchical structure. When the nonalphanumeric characters were used, a matrix structure emerged. Exps V–VII required 50 undergraduates to judge the dissimilarity of 2 sequences of grouped items, the 2nd of which (the variation) was a reordering of the 1st (the original). The variation was made by reordering the groups in the original, reordering positions within groups, or reordering both groups and positions. Results show that when the members of a group were able to be encoded as single verbal units, the data supported a hierarchical system. When this was not possible, a matrix system fitted the data best. It is concluded that there is no general code for representing the order of grouped sequences and that the results are more compatible with a theory that postulates a number of specific subsystems in short-term memory, each with its own format for preserving order, than one that assumes a generalized order code. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Skill learning in the elderly: Diminished implicit and explicit memory for a motor sequence.

Studied explicit and implicit memory for a cognitive-motor sequence in elderly and young adults. Implicit memory was examined in a serial reaction time (RT) paradigm in which sequences of hand postures repeated cyclically, then shifted to random sequences. Two control groups received random sequences throughout. Movement times (MTs) across the 1st 4 blocks did not improve more in the elderly-repeated than in the elderly-random group. In contrast, the young-repeated group showed greater improvement in MT across these blocks than the young-random group. MT was less affected in the elderly than in the young by shifts between repeated and random sequences, indicating impaired implicit memory. Explicit memory, which was assessed by free recall and cued recall, also was impaired in the elderly. Diminished implicit memory in the elderly could not be explained solely by the possible intrusion of conscious recollection strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immediate spatial order memory and item memory in sixth-grade children as a function of reader ability.

16 good and 16 poor 6th-grade readers served as Ss. Exp I tested immediate order memory for strings of 4 and 6 consonants that were either redundant (R) or nonredundant (NR) based on positional frequencies of letters in printed English. Both reader groups were better in retrieving order for R strings; poor readers were inferior to good readers on both R and NR 6-letter strings. Exp II tested for immediate order memory and immediate item memory for strings of 8 digits and strings of 8 consonants. Good readers were better than poor readers on all tasks. However, order memory appeared to be more strongly related to reading ability than was item memory. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in short-term memory for serial order: Data and a model.

Age-related deficits in short-term memory have been widely reported, but reduced overall scores could reflect increased order errors, increased omissions, or increased intrusions. Different explanations for reduced short-term memory with aging lead to different predictions. In this study, young (n?=?68; M age?=?20 years) and older (n?=?99; M age?=?65 years) adults were presented with lists of letters and were asked to recall each list immediately in the correct order. Age differences in error patterns were similar for auditory and visual presentation. For example, older adults made more errors of every type, and a greater proportion of the older adults' errors were omissions. An additional condition, in which older adults were encouraged to guess, ruled out an age increase in response threshold as a full explanation for the results. The data were modeled by an oscillator-based computational model of memory for serial order. A good fit to the aging data was achieved by simultaneously altering two parameters that were interpreted as corresponding to frontal decline and response slowing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What you get out of memory depends on the question you ask.

Following study, participants received 2 tests. The 1st was a recognition test; the 2nd was designed to tap recollection. The objective was to examine performance on Test 1 conditional on Test 2 performance. In Experiment 1, contrary to process dissociation assumptions, exclusion errors better predicted subsequent recollection than did inclusion errors. In Experiments 2 and 3, with alternate questions posed on Test 2, words having high estimates of recollection with one question had high estimates of familiarity with the other question. Results supported the following: (a) the 2-test procedure has considerable potential for elucidating the relationship between recollection and familiarity; (b) there is substantial evidence for dependency between such processes when estimates are obtained using the process dissociation and remember-know procedures; and (c) order of information access appears to depend on the question posed to the memory system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)