Age-related associative deficits and the isolation effect

ABSTRACT

If all but one of the items in a list are similar (e.g., all black except one red), memory for the different item is enhanced (the isolation effect). Older adults generally show similar or smaller isolation effects compared to young adults, which has been attributed to age-related deficits in associative memory whereby older adults are less able to associate an isolated stimulus to its isolating feature. Experiment 1 examined the isolation effect for isolation based on spatial position, modality and color; in Experiment 2, the criterion for isolation was the associative relation between stimuli. The results consistently showed no differences between young and older participants in the magnitude of the isolation effect. Whilst age deficits in associative memory may act to reduce the isolation effect in older adults, age deficits in self-initiated processing and inhibitory functionality may counteract this reduction by enhancing the isolation effect in older adults.     

The influence of age on memory for distinctive events

We examined whether memory for distinctive events is influenced by aging. To do so, we used a semantic isolation paradigm in which people show superior memory for a word when it is presented in a list of items from a different semantic category (e.g., the word table is presented in a list of all bird exemplars) as compared with when the same word (table) is presented in a list of unrelated words. Results showed that both younger and older adults demonstrated an isolation effect in memory, although older adults showed a numerically smaller isolation effect than did younger adults. Results suggest that in contrast with previous findings (Cimbalo & Brink, 1982), older adults can take advantage of this type of distinctiveness to aid memory performance.     

What causes the isolation effect?

Events that are incongruent with their prevailing context are usually very well remembered. This fact often is described as the distinctiveness effect in memory, an effect that has served as explanation not only of memory phenomena but also of various other phenomena, including social judgment. The core laboratory paradigm for studying distinctiveness in memory research has long been the isolation paradigm. This paradigm, sometimes attributed to H. von Restorff, yields better memory for an item categorically isolated from surrounding items than for the surrounding items and a proper control item. The authors offer an interpretation of the isolation effect based on the analysis of the processing of similarities and differences among the items. Two experiments provide evidence for this interpretation. The results are discussed in the context of current theories of distinctiveness effects in memory. An appeal is made for a different conceptualization of distinctiveness effects, one that treats distinctiveness as a discriminative process in memory that requires processing of both similarities and differences among items.     

Ageing and secondary-distinctiveness-based effects: The orthographic distinctiveness effect is more robust than the bizarreness effect

Differences related to ageing were investigated in two cases of secondary-distinctiveness-based effects: the bizarreness effect and the orthographic distinctiveness effect. A secondary distinctiveness effect means that items that are unusual compared to one's general knowledge stored in permanent memory are better remembered than common items. Experiment 1 confirmed that ageing diminishes the facilitative effects of bizarreness in a mixed list design with equal numbers of bizarre and common images. We suggest that the impaired bizarreness effect in older adults (above age 70) may be due to reduced attentional resources, since no bizarreness effect was observed for younger adults in the divided attention condition. Experiment 2 studied the orthographic distinctiveness effect in ageing for the first time. Contrary to our expectations, an orthographic distinctiveness effect was observed for all participants including older adults and younger adults in a divided attention condition. Because reduced attentional resources due to normal ageing or to experimental manipulation did not impact the facilitative effects of orthographic distinctiveness, our findings suggest that the orthographic distinctiveness effect may be mediated by more automatic processing.     

Aging and memory for words and action events: effects of item repetition and list length

We were concerned with the effects of item repetition, list length, and class of item on free recall in elderly as compared with young adults. In Experiment 1, samples of young and elderly adults recalled a list of 27 words and a list of 27 action events (minitasks performed by the subjects). Some items were presented once and some twice. Although the younger subjects showed better recall on both types of lists, the older sample benefited from item repetition as much as did the younger sample. This finding was replicated in Experiment 2. A second finding in Experiment 2 was a significant aging effect in the recall of long but not of short lists of both words and action events. The absence of an Age X Repetition Effect interaction was ascribed to the strength nature of the repetition manipulation. The age effects in the recall of the long lists were attributed to possible deficits in retrieval proficiency.     

Ageing and secondary-distinctiveness-based effects: The orthographic distinctiveness effect is more robust than the bizarreness effect

Differences related to ageing were investigated in two cases of secondary-distinctiveness-based effects: the bizarreness effect and the orthographic distinctiveness effect. A secondary distinctiveness effect means that items that are unusual compared to one's general knowledge stored in permanent memory are better remembered than common items. Experiment 1 confirmed that ageing diminishes the facilitative effects of bizarreness in a mixed list design with equal numbers of bizarre and common images. We suggest that the impaired bizarreness effect in older adults (above age 70) may be due to reduced attentional resources, since no bizarreness effect was observed for younger adults in the divided attention condition. Experiment 2 studied the orthographic distinctiveness effect in ageing for the first time. Contrary to our expectations, an orthographic distinctiveness effect was observed for all participants including older adults and younger adults in a divided attention condition. Because reduced attentional resources due to normal ageing or to experimental manipulation did not impact the facilitative effects of orthographic distinctiveness, our findings suggest that the orthographic distinctiveness effect may be mediated by more automatic processing.     

Evidence for time-based models of free recall

Is memory temporally organized? According to temporal distinctiveness models of memory, temporally isolated items should be better remembered than temporally crowded items in free recall tasks. Here, we tested this class of model by varying the temporal isolation of items either predictably (Experiment 1) or unpredictably (Experiment 2) in a free recall task. In both experiments, item recall probability increased as a function of the temporal gaps both before and after the item. The results are taken as support for temporal distinctiveness models of memory, in which items are represented and recalled in terms of their positions along a temporal dimension.     

Aging and the Ranschburg effect: no evidence of reduced response suppression in old age

Two experiments tested 1 aspect of L. Hasher and R. T. Zacks's (1988) reduced inhibition hypothesis, namely, that old age impairs the ability to suppress information in working memory that is no longer relevant. In Experiment 1, young and older adults were asked to recall lists of letters in the correct order. Half of the lists contained repeated items while half were control lists. Recall of nonadjacent repeated items was worse than that of control items. This Ramschburg effect was larger (i.e., greater response suppression) in older than in young adults. In Experiment 2, young and older adults were required either to recall the list or to report if there was a repeated item. Repetition detection was high and similar in the 2 age groups. When age differences in overall performance were taken into account, there was evidence of increased repetition inhibition with age in both experiments. Thus, contrary to the general reduced inhibition hypothesis, the specific process of response suppression during serial recall is not reduced by aging.     

Revisiting von Restorff’s early isolation effect

An item that is conceptually or physically different from other items in a series is often remembered well. This isolation effect has been found independent of the position of the isolated item in the list, suggesting that special attention to or processing of the isolated item is not a necessary precondition of the effect. Three experiments are reported that challenge this conclusion. In Experiment 1a, we compared memory for conceptually isolated items to memory for the same items in unrelated and homogeneous lists. Under moderately distracting conditions, isolation effects were observed with midlist but not with early isolates. In fact, early isolation impaired memory for the conceptually distinct items relative to the same items in homogeneous lists. Experiment 1b replicated this memory impairment for early conceptual isolates and extended it to nondistracting conditions. In Experiment 2, we focused on early isolation, manipulating the type of isolation and whether or not participants performed judgments of learning (JOLs). An early isolation effect was observed for numbers isolated in lists of words (and vice versa), but not for conceptual isolates. Performing the JOL task reduced the size of the early isolation effect. These results suggest that number/word stimulus contrasts are coded automatically and support an isolation effect independent of list position. However, conceptual contrasts require relational processing and will only support an early isolation effect when such processing occurs. The results of Experiments 1a, 1b, and 2 suggest that attentional resources during list presentation and a favorable retrieval environment combine to support good memory for distinctive events.     

Long-term effects of testing on the recall of nontested materials

The isolation paradigm is a staple in the study of distinctiveness and memory. Isolated items are better remembered than non-isolated controls, and the standard interpretation of this effect is that subjective experience of salience recruits extraordinary processing to the isolated item. This interpretation is at odds with data showing an isolation effect when the isolate is not perceived as salient (e.g., von Restorff, 1933). All available research on the early isolation effect has tested memory after a relatively short retention interval. Perhaps the effect of salience on memory in the isolation paradigm would be revealed following longer retention intervals. The experiment reported here examines the effect of isolation following a 48-hour retention interval when the isolate evokes an experience of salience compared to when the isolate does not evoke that reaction. The isolation effect was substantial after the 48-hour delay but equally so for early and late isolation. Salience appears to have nothing to do with the memory processes even at the longer retention intervals.     

A hybrid-similarity exemplar model for predicting distinctiveness effects in perceptual old-new recognition

In 2 sets of experiments, the authors investigated the basis for old-item distinctiveness effects in perceptual recognition, whereby distinctive old items are recognized with higher probability than are typical old items. In Experiment 1, distinctive old items were defined as those lying in isolated regions of a continuous-dimension similarity space. In this case, any beneficial effects of distinctiveness were absent or small, regardless of the structure of the test list used to assess recognition memory. In Experiment 2, distinctive items were defined as those objects containing certain discrete, individuating features. In this case, large old-item distinctive effects were observed, with the nature of the effects being modulated by the structure of the test lists. A hybrid-similarity exemplar model, combining elements of continuous-dimension distance and discrete-feature matching, was used to account for these distinctiveness effects in the recognition data.     

The effects of emotional content and aging on false memories

After studying a list of words related to a nonpresented lure word, people often falsely recall or recognize the nonpresented lure. Older adults are particularly susceptible to these forms of false memories. The age-related false memory enhancement likely occurs because older adults do not encode, or later retrieve, items in enough detail to allow them to discriminate between presented words and other associated but nonpresented items. Pesta, Murphy, and Sanders (2001) suggested that the emotional salience of the lures may provide distinctiveness, so that individuals would be less likely to endorse an emotional lure as a studied item than to endorse a neutral lure. In the present investigation, young and older adults were less likely to falsely recall or recognize emotional, as compared with neutral, lures. Both age groups appeared capable of using the distinctiveness of the emotional lures to reduce, although not to eliminate, false recall and recognition.     

Episodic priming and memory for temporal source: event-related potentials reveal age-related differences in prefrontal functioning.

Event-related potentials (ERPs) were recorded from young (M = 25) and older (M = 71) adults during a recognition memory paradigm that assessed episodic priming. Participants studied two temporally distinct lists of sentences (each with two unassociated nouns). At test, in response to the nouns, participants made old-new, followed by remember (context)-know (familiarity) and source (i.e., list) judgments. Both young and older adults showed equivalent episodic priming effects. However, compared to the young adults, the older adults showed a greater source performance decrement than item memory performance decrement. Both age groups showed equivalent posterior-maximal old-new ERP effects. However, only the young produced a frontal-maximal, late onset old-new effect that differed as a function of subsequent list attribution. Because source memory is thought to be mediated by prefrontal cortex, we conclude that age-related memory differences may be due to a deficit in a prefrontal cortical system that underlies source memory and are not likely to be due to an age-related decline in episodic priming.     

Prioritization within visual working memory reflects a flexible focus of attention

When motivated, people can keep nonrecent items in a list active during the presentation of new items, facilitating fast and accurate recall of the earlier items. It has been proposed that this occurs by flexibly orienting attention to a single prioritized list item, thus increasing the amount of attention-based maintenance directed toward this item at the expense of other items. This is manipulated experimentally by associating a single distinct feature with a higher reward value, such as a single red item in a list of black items. These findings may be more parsimoniously explained under a distinctiveness of encoding framework rather than a flexible attention allocation framework. The retrieval advantage for the prioritized list position may be because the incongruent feature stands out in the list perceptually and causes it to become better encoded. Across three visual working memory experiments, we contrast a flexible attention theory against a distinctiveness of encoding theory by manipulating the reward value associated with the incongruent feature. Findings from all three experiments show strong support in favor of the flexible attention theory and no support for the distinctiveness of encoding theory. We also evaluate and find no evidence that strategy use, motivation, or tiredness/fatigue associated with reward value can adequately explain flexible prioritization of attention. Flexible attentional prioritization effects may be best understood under the context of an online attentional refreshing mechanism.

     

False recognition in younger and older adults: Exploring the characteristics of illusory memories

Roediger and McDermott (1995) demonstrated that when subjects hear a list of associates to a “theme word” that has itself not been presented, they frequently claim to recollect having heard the nonpresented theme word on the study list. In Experiment 1, we found that asking subjects to explain theirremember responses, by writing down exactly what they remembered about the item’s presentation at study, did not significantly diminish the rate ofremember false alarms to nonpresented theme words. We also found that older adults were relatively more susceptible than younger adults to this false-recognition effect. Subjects’ explanations suggested that both veridical and illusory memories were predominantly composed of associative information as opposed to sensory and contextual detail. In Experiment 2, we obtained quantitative evidence for this conclusion, using a paradigm in which subjects were asked focused questions about the contents of their recollective experience. Lastly, we found that both younger and older adults recalled more sensory and contextual detail in conjunction with studied items than with nonpresented theme words, although these differences were less pronounced in older adults.     

Emotional Salience and the Isolation Effect

When a homogeneous list contains a few items that are different from the rest of the items in the list, these isolated items show enhanced recall compared to the same items in a list where these items are not isolated. This phenomenon, known as the isolation effect, has been explained on the basis of isolated items eliciting salience. In this experiment, negative pictures and neutral pictures were isolated at the early and late part of the list. The salience explanation would predict that participants would pay more attention to these isolated items resulting in higher judgments of learning (JOL) ratings compared to the same items in the control list. Negative pictures showed the isolation effect for both early and late isolation; however, for early isolation, JOL was similar between the isolated and non-isolated pictures indicating that the emotional isolation effect does not require emotional salience.     

Aging,imagery, and the bizarreness effect

ABSTRACT

This study examined the bizarre imagery effect in young and older adults, under incidental and intentional conditions. Intentionality was manipulated across experiments, with participants receiving an incidental free recall test in Experiment 1 and an intentional test in Experiment 2. This study also examined the relation between working memory resources and the bizarreness effect. In Experiment 1 young and older adults were presented with common and bizarre sentences; they later received an incidental recall test. There were no age differences in sensitivity to the bizarreness effect in Experiment 1 when ANOVAs were used to analyze the data. However, when the bizarreness effect was examined in terms of effect size, there was evidence that younger adults produced larger bizarreness effect sizes than younger adults. Experiment 2 further explored age differences in sensitivity to the bizarreness effect by presenting young and older adults with bizarre and common sentences under intentional learning conditions. Experiment 2 failed to yield age differences as a function of item type (bizarre vs. common). In addition, Experiment 2 failed to yield significant evidence that the bizarreness effect is modulated by working memory resources. The results of this study are most consistent with the distinctiveness account of the bizarreness effect.     

Aging, imagery, and the bizarreness effect

ABSTRACT This study examined the bizarre imagery effect in young and older adults, under incidental and intentional conditions. Intentionality was manipulated across experiments, with participants receiving an incidental free recall test in Experiment 1 and an intentional test in Experiment 2. This study also examined the relation between working memory resources and the bizarreness effect. In Experiment 1 young and older adults were presented with common and bizarre sentences; they later received an incidental recall test. There were no age differences in sensitivity to the bizarreness effect in Experiment 1 when ANOVAs were used to analyze the data. However, when the bizarreness effect was examined in terms of effect size, there was evidence that younger adults produced larger bizarreness effect sizes than younger adults. Experiment 2 further explored age differences in sensitivity to the bizarreness effect by presenting young and older adults with bizarre and common sentences under intentional learning conditions. Experiment 2 failed to yield age differences as a function of item type (bizarre vs. common). In addition, Experiment 2 failed to yield significant evidence that the bizarreness effect is modulated by working memory resources. The results of this study are most consistent with the distinctiveness account of the bizarreness effect.     

Word frequency influences on the list length effect and associative memory in young and older adults

Many studies show that age deficits in memory are smaller for information supported by pre-experimental experience. Many studies also find dissociations in memory tasks between words that occur with high and low frequencies in language, but the literature is mixed regarding the extent of word frequency effects in normal ageing. We examined whether age deficits in episodic memory could be influenced by manipulations of word frequency. In Experiment 1, young and older adults studied short and long lists of high- and low-frequency words for free recall. The list length effect (the drop in proportion recalled for longer lists) was larger in young compared to older adults and for high- compared to low-frequency words. In Experiment 2, young and older adults completed item and associative recognition memory tests with high- and low-frequency words. Age deficits were greater for associative memory than for item memory, demonstrating an age-related associative deficit. High-frequency words led to better associative memory performance whilst low-frequency words resulted in better item memory performance. In neither experiment was there any evidence for age deficits to be smaller for high- relative to low-frequency words, suggesting that word frequency effects on memory operate independently from effects due to cognitive ageing.