Retrieval during learning facilitates subsequent memory encoding.

In multiple-list learning, retrieval during learning has been suggested to improve recall of the single lists by enhancing list discrimination and, at test, reducing interference. Using electrophysiological, oscillatory measures of brain activity, we examined to what extent retrieval during learning facilitates list encoding. Subjects studied 5 lists of items in anticipation of a final cumulative recall test and did either a retrieval or a no-retrieval task between study of the lists. Retrieval was from episodic memory (recall of the previous list), semantic memory (generation of exemplars from an unrelated category), or short-term memory (2-back task). Behaviorally, all 3 forms of retrieval enhanced recall of both previously and subsequently studied lists. Physiologically, the results showed an increase of alpha power (8–14 Hz) from List 1 to List 5 encoding when no retrieval activities were interpolated but no such increase when any of the 3 retrieval activities occurred. Brain–behavior correlations showed that alpha-power dynamics from List 1 to List 5 encoding predicted subsequent recall performance. The results suggest that, without intermittent retrieval, encoding becomes ineffective across lists. In contrast, with intermittent retrieval, there is a reset of the encoding process for each single list that makes encoding of later lists as effective as encoding of early lists. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Intact and impaired conceptual memory processes in amnesia.

To examine the status of conceptual memory processes in amnesia, a conceptual memory task with implicit or explicit task instructions was given to amnesic and control groups. After studying a list of category exemplars, participants saw category labels and were asked to generate as many exemplars as possible (an implicit memory task) or to generate exemplars that had been in the prior study list (an explicit memory task). After incidental deep or shallow encoding of exemplars, amnesic patients showed normal implicit memory performance (priming), a normal levels-of-processing effect on priming, and impaired explicit memory performance. After intentional encoding of exemplars, amnesic patients showed impaired implicit and explicit memory performance. Results suggest that although amnesic patients can show impairments on implicit and explicit conceptual memory tasks, their deficit does not generalize to all conceptual memory tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of category length and strength on familiarity in recognition.

In most recognition models a decision is based on a global measure often termed familiarity. However, a response criterion is free to vary across lists varying in length and strength, making familiarity changes immeasurable. We presented a single list with a mixture of exemplars from many categories, so that the criterion would be unlikely to vary with length or strength of the category of the test item. False alarms rose with category length but not category strength, suggesting that familiarity does not change much with changes in strength of other items but grows when additional items are studied. The results were well fit by an extension of the search of associative memory (SAM) model presented by R. M. Shiffrin, R. Ratcliff, and S. E. Clark (see record 1990-13917-001). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of bilingualism, aging, and semantic relatedness on memory under divided attention.

We examined how encoding and retrieval processes were affected by manipulations of attention, and whether the degree of semantic relatedness between words in the memory and distracting task modulated these effects. We also considered age and bilingual status as mediating factors. Monolingual and bilingual younger and older adults studied a list of words from a single semantic category presented auditorily, and later free recalled them aloud. During either study or retrieval, participants concurrently performed a distracting task requiring size decisions to words from either the same or a different semantic category as the words in the memory task. The greatest disruptions of memory from divided attention (DA) were for encoding rather than retrieval. The effect of semantic relatedness was significant only for DA at encoding. Older age and bilingualism were associated with lower recall scores in all conditions, but these factors did not influence the magnitude of memory interference. The results suggest that encoding is more sensitive to semantic similarity in a distracting task than is retrieval. The role of attention at encoding and retrieval is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differentiation and response bias in episodic memory: Evidence from reaction time distributions.

In differentiation models, the processes of encoding and retrieval produce an increase in the distribution of memory strength for targets and a decrease in the distribution of memory strength for foils as the amount of encoding increases. This produces an increase in the hit rate and decrease in the false-alarm rate for a strongly encoded compared with a weakly encoded list, consistent with empirical data. Other models assume that the foil distribution is unaffected by encoding manipulations or the foil distribution increases as a function of target strength. They account for the empirical data by adopting a stricter criterion for strongly encoded lists relative to weakly encoded lists. The differentiation and criterion shift explanations have been difficult to discriminate with accuracy measures alone. In this article, reaction time distributions and accuracy measures are collected in a list-strength paradigm and in a response bias paradigm in which the proportion of test items that are targets is manipulated. Diffusion model analyses showed that encoding strength is primarily accounted for by changes in the rate of accumulation of evidence (i.e., drift rate) for both targets and foils and manipulating the proportion of targets is primarily accounted for by changes in response bias (i.e., starting point). The diffusion model analyses is interpreted in terms of predictions of the differentiation models in which subjective memory strength is mapped directly onto drift rate and criterion placement is mapped onto starting point. Criterion shift models require at least 2 types of shifts to account for these findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A context noise model of episodic word recognition.

Item noise models of recognition assert that interference at retrieval is generated by the words from the study list. Context noise models of recognition assert that interference at retrieval is generated by the contexts in which the test word has appeared. The authors introduce the bind cue decide model of episodic memory, a Bayesian context noise model, and demonstrate how it can account for data from the item noise and dual-processing approaches to recognition memory. From the item noise perspective, list strength and list length effects, the mirror effect for word frequency and concreteness, and the effects of the similarity of other words in a list are considered. From the dual-processing perspective, process dissociation data on the effects of length. temporal separation of lists, strength, and diagnosticity of context are examined. The authors conclude that the context noise approach to recognition is a viable alternative to existing approaches. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dimensions of everyday memory in age-associated memory impairment.

A battery of tests that uses computer and laser disk technology to simulate learning and memory tasks of everyday life, such as recalling names after introduction and remembering items on a grocery list, is described. The performance of 110 persons suffering Age-Associated Memory Impairment was factor analyzed and yielded everyday memory dimensions of verbal memory, visual memory, psychomotor speed, attention, and vigilance. These computerized performance dimensions are associated with relevant standard clinical measures of memory performance, such as the Benton Visual Retention Test and the Wechsler Memory Scale Paired-Associated Learning and Logical Memory subtests. The clinical and research utility of the computerized measures and the new diagnostic category of Age-Associated Memory Impairment are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Judgments of frequency and recognition memory in a multiple-trace memory model.

The multiple-trace simulation model, {minerva} 2, was applied to a number of phenomena found in experiments on relative and absolute judgments of frequency, and forced-choice and yes–no recognition memory. How the basic model deals with effects of repetition, forgetting, list length, orientation task, selective retrieval, and similarity and how a slightly modified version accounts for effects of contextual variability on frequency judgments were shown. Two new experiments on similarity and recognition memory were presented, together with appropriate simulations; attempts to modify the model to deal with additional phenomena were also described. Questions related to the representation of frequency are addressed, and the model is evaluated and compared with related models of frequency judgments and recognition memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short term memory for numerousness in schizophrenic young adults

The short term memory of schizophrenics for random dot patterns was examined by a delayed comparison procedure. In experiment 1, the 10 schizophrenics and 10 normals compared a fixed dot pattern (standard) with a variable dot pattern (compairson) appearing 2 or 8 seconds later and decided whether the comparison stimulus had "more" or "less" dots than the standard. Memory strength, indexed by the d' value of signal-detection theory, showed neither group difference nor decay over time. In experiment 2, the interstimulus interval was filled with an unjudged dot pattern (storage interference), and the standard stimulus followed the variable comparison stimulus (encoding difficulty). The memory strength of 17 schizophrenics and 17 normals was severely impaired, and their memory strength weakened over time, but again, no group differences were found. In both experiments, the two groups showed a strong bias (beta) in underestimating the first (to-be-remembered) stimulus. It was concluded that schizophrenics' short term perceptual memory for nonverbal stimuli remains good.     

On the nature of the decision axis in signal-detection-based models of recognition memory.

Most models of recognition memory involve a signal-detection component in which a criterion is placed along a decision axis. Older models generally assume a familiarity-decision axis, but newer models often assume a likelihood ratio axis instead because it allows for a more natural account of the ubiquitous mirror effect. In 3 experiments reported here, item strength was differentially manipulated to see whether a mirror effect would occur. Within a list, the items from 1 category were strengthened by repetition, but the items from another category were not. On the subsequent recognition test, the hit rate was higher for the strong category, but the false-alarm rates for the weak and strong categories were the same (i.e., no mirror effect was observed). This result suggests that the decision axis represents a familiarity scale and that participants adopt a single decision criterion that they maintain throughout the recognition test. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of intentionality and strategy on memory for frequency.

Several studies have examined whether Ss who learn a list of words incidentally remember frequency as well as those who learn the words intentionally. Conflicting results have been found. This discrepancy is examined in the present 3 experiments with a total of 105 undergraduates. Results of Exps I and II indicate that intentional-learning Ss exhibited an advantage in memory for frequency only if the instructions emphasized the importance of good performance on the memory task. Results of Exp III show that intentionality influenced memory for frequency within a list of items and that a strategy that involved semantic processing led to improved frequency estimation. It is concluded that these results are inconsistent with formulations of the claim that frequency information is encoded automatically and demonstrate that instructions play a crucial mediating role in memory for frequency. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event-related potentials of verbal encoding into episodic memory: dissociation between the effects of subsequent memory performance and distinctiveness

Episodic memory encoding and distinctiveness detection were examined using event-related potentials (ERP) in a single-trial word list learning paradigm with free recall following distraction. To manipulate distinctiveness, encoding of high- and very low-frequency words was contrasted. Amplitudes of the N400 and late positive component (LPC) were larger for low- than for high-frequency words, and ERPs were more positive for subsequently recalled than not recalled words. This subsequent memory effect was dissociated from the correlates of distinctiveness by polarity for the N400 and by time course for the LPC and dissociable into two effects. The data suggest that the first subsequent memory effect, which occurred for both word categories, is more directly related to episodic memory formation, whereas the second effect, which occurred for high-frequency words only, is related to processes influencing episodic encoding success indirectly.     

Testing global memory models using ROC curves.

Global memory models are evaluated by using data from recognition memory experiments. For recognition, each of the models gives a value of familiarity as the output from matching a test item against memory. The experiments provide ROC (receiver operating characteristic) curves that give information about the standard deviations of familiarity values for old and new test items in the models. The experimental results are consistent with normal distributions of familiarity (a prediction of the models). However, the results also show that the new-item familiarity standard deviation is about 0.8 that of the old-item familiarity standard deviation and independent of the strength of the old items (under the assumption of normality). The models are inconsistent with these results because they predict either nearly equal old and new standard deviations or increasing values of old standard deviation with strength. Thus, the data provide the basis for revision of current models or development of new models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integration of the ecological and error models of overconfidence using a multiple-trace memory model.

A memory processes account of the calibration of probability judgments was examined. A multiple-trace memory model, Minerva-Decision Making (MDM; M. R. P. Dougherty, C. F. Gettys, & E. E. Ogden, 1999), used to integrate the ecological (Brunswikian) and the error (Thurstonian) models of overconfidence, is described. The model predicts that overconfidence should decrease both as a function of experience and as a function of encoding quality. Both increased experience and improved encoding quality result in lower variance in the output of the model, which in turn leads to improved calibration. Three experiments confirmed these predictions. Implications of MDM's account of overconfidence are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling intrusions and correct recall in episodic memory: Adult age differences in encoding of list context.

A model for correct recall and intrusions in cued recall of word lists is introduced. Intrusions are false responses that were correct in an earlier list. The model assumes 3 exclusive states for memory traces after encoding: with a list tag (i.e., with information about list origin), without list tags, and missing. Across lists, a trace can lose its list tag or its content. For retrieval, an optimal strategy of response selection was assumed. Younger and older laboratory-trained mnemonists participated in 2 experiments in which recall of permutations of a single word list across a single set of cues was held constant with individually adjusted presentation times. With correct recall equated to younger adults, older adults were more susceptible to intrusions. Age differences were restricted to model parameters estimating the probability of generation of list tags. Alternative accounts of age differences in context memory are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term memory in autism spectrum disorder.

Three experiments examined verbal short-term memory in comparison and autism spectrum disorder (ASD) participants. Experiment 1 involved forward and backward digit recall. Experiment 2 used a standard immediate serial recall task where, contrary to the digit-span task, items (words) were not repeated from list to list. Hence, this task called more heavily on item memory. Experiment 3 tested short-term order memory with an order recognition test: Each word list was repeated with or without the position of 2 adjacent items swapped. The ASD group showed poorer performance in all 3 experiments. Experiments 1 and 2 showed that group differences were due to memory for the order of the items, not to memory for the items themselves. Confirming these findings, the results of Experiment 3 showed that the ASD group had more difficulty detecting a change in the temporal sequence of the items. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Familiarity breeds differentiation: a subjective-likelihood approach to the effects of experience in recognition memory

With repeated exposure, people become better at identifying presented items and better at rejecting items that have not been presented. This differentiation effect is captured in a model consisting of item detectors that learn estimates of conditional probabilities of item features. The model is used to account for a number of findings in the recognition memory literature, including (a) the basic differentiation effect (strength-mirror effect), (b) the fact that adding items to a list reduces recognition accuracy (list-length effect) but extra study of some items does not reduce recognition accuracy for other items (null list-strength effect), (c) nonlinear effects of strengthening items on false recognition of similar distractors, (d) a number of different kinds of mirror effects, (e) appropriate z-ROC curves, and (f) one type of deviation from optimality exhibited in recognition experiments.     

The relation of ERP components to complex memory processing

The relation between various ERP components generated during encoding of a word and its subsequent recall were investigated using a "rote" serial-order and an "elaborative" category memory task. Words (flashed separately) were time-locked to EEG recordings from 21 cortical sites. ERP components from the five subjects having the highest recall scores were compared to the five lowest scoring subjects. Results based on the P200 peak amplitude data as well as the N400 and late positive component peak amplitude and latency data suggest that anterior and posterior distributional differences are elicited during encoding of words for rote and elaborative memory tasks. Furthermore, strong individual differences in these patterns were found as a function of task. A tentative argument was made that the obtained anterior and posterior differences may index different word feature selection and encoding processes, which are differentially utilized by high and low recallers.     

Differential effects of aging and Alzheimer's disease on conceptual implicit and explicit memory.

The effects of aging and Alzheimer's disease (AD) on conceptual explicit and implicit memory were examined. Three groups of participants patients with AD; age-matched, older control participants; and younger control participants made deep (semantic) or shallow (nonsemantic) judgments about low-dominant category exemplars. Explicit memory was measured by category cued recall and implicit memory was measured by priming on a category-exemplar generation task. Younger participants had enhanced cued recall and priming following deep, relative to shallow, encoding; this indicated that both memory measures were conceptually driven. Aging reduced explicit, but not implicit, test performance, and it did not reduce conceptually driven processes for either test. In contrast, AD reduced explicit and implicit test performance, and it impaired conceptually driven memory processes for both tests. (PsycINFO Database Record (c) 2010 APA, all rights reserved)