Effects of Age and Divided Attention on Memory Components Derived for the Category Exemplar Generation Task

ABSTRACT

Age differences in memory performances on a conceptually driven task, the category exemplar generation (CEG) test, were investigated. Thirty-six younger adults and 36 healthy older adults studied word lists in full and divided attention conditions. Recall was tested with category names. The process-dissociation procedure was used to derive estimates of controlled and automatic memory. Old-old adults (70–84 years) exhibited poorer conscious recollection than both younger (18–24) and young-old adults (59–69). In contrast, no age differences were found in estimates of automatic memory. For the younger and older adults, the divided encoding manipulation reduced both the consciously controlled and automatic estimates of memory. The results suggest that the few prior findings of age deficits in priming on the CEG may have been an artifact of contamination from conscious retrieval processes. They also indicate that the opportunity for greater semantic processing enhances the conceptual priming of both younger and older adults.     

A computational approach to modeling population differences

Four experiments were conducted to determine whether the Hyperspace Analogue to Language (HAL) model of semantic memory could differentiate between two different populations. An analysis of the differences in densities (or average distances between word neighbors in semantic space) in HAL matrices—generated from text corpora derived from younger and older adults—confirmed that HAL was able to distinguish between the two age groups. This difference was again detected when structured interview data were used to build the corpora. A third experiment, designed to test the specificity of HAL in detecting differences between groups, did not detect any difference in the densities of the memory representations when older adults generated both the test corpora. The final experiment, conducted on the language of adults with Alzheimer’s and normal adults, again demonstrated that HAL could discriminate between the two populations. These results suggest that HAL is capable of modeling, on the basis of changes in mean density, some of the differences between populations without modifying the model itself but, rather, by changing the text corpus from which the model creates its representations in semantic space.     

Effects of age and divided attention on memory components derived for the category exemplar generation task

Age differences in memory performances on a conceptually driven task, the category exemplar generation (CEG) test, were investigated. Thirty-six younger adults and 36 healthy older adults studied word lists in full and divided attention conditions. Recall was tested with category names. The process-dissociation procedure was used to derive estimates of controlled and automatic memory. Old-old adults (70-84 years) exhibited poorer conscious recollection than both younger (18-24) and young-old adults (59-69). In contrast, no age differences were found in estimates of automatic memory. For the younger and older adults, the divided encoding manipulation reduced both the consciously controlled and automatic estimates of memory. The results suggest that the few prior findings of age deficits in priming on the CEG may have been an artifact of contamination from conscious retrieval processes. They also indicate that the opportunity for greater semantic processing enhances the conceptual priming of both younger and older adults.     

Adult age differences in attention to semantic context

In three experiments age differences in attention to semantic context were examined. The performance of younger adults (ages 18-29 years) and older adults (ages 60-79 years) on a semantic priming task indicated that both age groups could use information regarding the probability that a prime and target would be related to flexibly anticipate the target category given the prime word (Experiment 1). The timing by which target expectancies were reflected in reaction time performance was delayed for older adults as compared to younger adults, but only when the target was expected to be semantically unrelated to the prime word (Experiment 2). When the target and prime were expected to be semantically related, the time course of priming effects was similar for younger and older adults (Experiment 3). Together the findings indicate that older adults are able to use semantic context and the probability of stimulus relatedness to anticipate target information. Although aging may be associated with a delay in the timing by which controlled expectancies are expressed, these findings argue against an age-related decline in the ability to represent contextual information.     

Effects of depth-of-processing and ageing on word-stem and word-fragment implicit memory tasks: Test of the lexical-processing hypothesis

The joint effects of depth-of-processing and age on repetition priming in implicit memory tests of word-fragment completion (WFC) and word-stem completion (WSC) were investigated. The experiment consisted of three study tasks (perceptual, lexical, and semantic) and four memory conditions: implicit (WSC and WFC) and explicit (WS cued recall and WF cued recall). In the WSC condition, semantic and lexical study processing produced equal priming, both superior to the perceptual study processing, whereas the WFC test showed equal priming for these three study conditions. This finding provides clear evidence, consistent with the lexical-processing hypothesis, that depth-of-processing in WSC priming reflects a lexical rather than a semantic process. It also provides support for the view that WSC and WFC involve different processes. However, there was no evidence of an age effect on either of these two implicit tasks. The data also revealed an overall significant effect of age and depth-of-processing, and an interaction between these variables on explicit cued recall tasks, indicating that older adults benefited less than younger ones from a deep encoding condition.     

Age-related differences in inference revision processing

In comparison to younger adults, older adults demonstrate deficiencies in cognitive and linguistic abilities. Such cognitive factors that decline with age include working memory capacity and inhibitory abilities. The purpose of the present investigation was to measure differences in time course processing of inference revision abilities, as well as working memory, as they exist relative to adult age differences. Fifteen neurologically intact older adults and 15 younger adults participated in this study. A cross-modal lexical priming paradigm was chosen as the measure of the inference revision task; the listening span task of Tompkins, Bloise, Timko, and Baumgaertner (1994) was selected as the measure of working memory. Both groups demonstrated normal priming effects. No age-related differences were found on the working memory measure. Age-related differences did emerge on inferencing abilities. A significant correlation emerged between the older group's performance on comprehending inference revisions and their working memory capacity. Generally, inhibitory abilities and working memory capacity appeared to adversely affect older participant's performance.     

Priming effects in prospective memory

Abstract

The objective of this study was to examine whether an increased activation of knowledge structures facilitates memory for future actions. Priming effects were manipulated by giving subjects a category fluency task for half of the target categories used in the subsequent prospective memory task. In this task, younger and older adults performed an action whenever an instance of a given semantic category occurred in the context of a free association task. The degree of retrieval support was varied by using typical and atypical category instances as targets. Although reliable priming effects were observed for both age groups, the magnitude of priming interacted with the degree of retrieval support. Older adults showed priming effects for typical targets only, whereas the opposite pattern of results was obtained for younger adults. These findings indicate that, in addition to retrieval-related factors, the operations performed at the time of planning also contribute to optimal prospective remembering.     

Level of processing and age affect involuntary conceptual priming of weak but not strong associates

Memory for weak and strong semantic associates was compared in intentional associate-cued-recall and incidental free-association tests. This design yielded four conditions (weak/intentional, strong/intentional, weak/incidental, and strong/ incidental) on which younger and older adults were compared. Level of processing (LOP) and age effects occurred for the weak/intentional, strong/intentional, and weak/incidental conditions, but not for the strong/incidental condition. Because participants could not distinguish weak from strong associates during the memory tests, these results suggest that free-association priming was involuntary and was not contaminated by voluntary retrieval strategies. Instead, they suggest that encoding deficits related to shallower LOP and older age reduce involuntary free-association priming mainly for associates without cohesive preexperimental representations.     

Searching for the Trace: The Influence of Age, Lexical Activation and Working Memory on Sentence Processing

To investigate the stability of trace reactivation in healthy older adults, 22 older volunteers with no significant neurological history participated in a cross-modal priming task. Whilst both object relative center embedded (ORC) and object relative right branching (ORR) sentences were employed, working memory load was reduced by limiting the number of words separating the antecedent from the gap for both sentence types. Analysis of the results did not reveal any significant trace reactivation for the ORC or ORR sentences. The results did reveal, however, a positive correlation between age and semantic priming at the pre-gap position and a negative correlation between age and semantic priming at the gap position for ORC sentences. In contrast, there was no correlation between age and priming effects for the ORR sentences. These results indicated that trace reactivation may be sensitive to a variety of age related factors, including lexical activation and working memory. The implications of these results for sentence processing in the older population are discussed.     

Adult Age Differences in Attention to Semantic Context

ABSTRACT

In three experiments age differences in attention to semantic context were examined. The performance of younger adults (ages 18–29 years) and older adults (ages 60–79 years) on a semantic priming task indicated that both age groups could use information regarding the probability that a prime and target would be related to flexibly anticipate the target category given the prime word (Experiment 1). The timing by which target expectancies were reflected in reaction time performance was delayed for older adults as compared to younger adults, but only when the target was expected to be semantically unrelated to the prime word (Experiment 2). When the target and prime were expected to be semantically related, the time course of priming effects was similar for younger and older adults (Experiment 3). Together the findings indicate that older adults are able to use semantic context and the probability of stimulus relatedness to anticipate target information. Although aging may be associated with a delay in the timing by which controlled expectancies are expressed, these findings argue against an age-related decline in the ability to represent contextual information.     

Examining the Response Competition Hypothesis of Age Effects in Implicit Memory

ABSTRACT

Age reductions in priming have been explained by differences in processing demands across implicit memory tests. According to one hypothesis, older adults show reduced priming relative to younger adults on implicit tests that require production of a response because these tests typically allow for response competition. In contrast, older adults do not show reductions in priming on identification tests that contain little response competition. The following experiments tested the specific role of response competition in mediating age effects in implicit memory. In Experiment 1, younger and older adults studied a list of words and were then given an implicit test of word stem completion. They studied a second list of words and were given an implicit test of general knowledge. Each implicit test contained items with unique solutions (the low response competition condition) and items with multiple solutions (the high response competition condition). In Experiment 2, younger and older adults were given explicit versions of the word stem completion and the general knowledge tests. Results showed an effect of age on explicit memory (Experiment 2), but no effect of age or response competition on priming (Experiment 1). Results are inconsistent with the theory that response competition leads to age effects on production tests of implicit memory.     

Age vs Alzheimer's: a computational model of changes in representation

Previous research has demonstrated that the language of older adults leads to denser representations in a high dimensional model of memory than does the language of younger adults (Conley & Burgess, in press), and thus that density in the model (HAL or the hyperspace analogue to language) may constitute a useful metric in comparing memory for younger and older adults. This paper extends the previous research by examining the role of density in semantic representations that emerged from the language generated by adults with Alzheimer' s and comparing the results with age-matched normal controls. We found that, just as older adults have denser representations in semantic space than do younger adults, adults with Alzheimer's have still denser representations than normal older adults. These results support the hypothesis that greater density, normally associated in the model with good semantic depth, may in fact reach a "saturation point" and affect retrieval in older adults and especially adults with Alzheimer's.     

Professional expertise does not eliminate age differences in imagery-based memory performance during adulthood.

Using a testing-the-limits paradigm, the authors investigated the modulation (attenuation) of negative adult age differences in imagery-based memory performance as a function of professional expertise. Six older graphic designers, 6 normal older adults, 6 younger graphic design students, and 6 normal younger students participated in a 19-session program with a cued-recall variant of the Method of Loci. Older graphic designers attained higher levels of mnemonic performance than normal older adults but were not able to reach younger adults' level of performance; a perfect separation of age groups was achieved. Spatial visualization was a good predictor of mnemonic performance. Results suggest that negative adult age differences in imagery-based memory are attenuated but not eliminated by the advantages associated with criterion-relevant ability (talent) and experience.     

Further evidence that negative priming in the Stroop color-word task is equivalent in older and younger adults

In 2 experiments, possible adult age differences in negative priming were explored using several variants of the Stroop color-word task. Negative priming was at least as high in the older adults as in the younger adults in every variant. Negative priming varied as a function of condition, but the age equivalence was unaffected. This result was true even when the possibility of general slowing was taken into account. Across conditions, interference and negative priming were positively correlated. The results do not permit a clear choice between the 2 major theoretical explanations of negative priming, inhibition and memory retrieval; they do show that negative priming can be systematically manipulated within an experimental paradigm.     

A speed-accuracy analysis of word recognition in young and older adults

To measure age differences in the rate of semantic priming, studies vary the prime-target interval in lexical decision (LD) tasks. This provides no time limit on the target response. Thus, older adults' greater response times (RTs) could offer them more accumulated priming at the response compared with younger, faster adults. This study used a response deadline procedure in an LD task to equalize processing time across age groups. Although RTs did not significantly differ across age groups, older adults showed larger semantic priming effects than young adults. Semantic priming was also found with response accuracy (d'), but did not differ across age.     

Process dissociation procedure reveals age differences in unconscious influences on memory for possible and impossible objects

Abstract

Forty-eight younger and 48 older adults performed inclusion and exclusion tasks for line drawings of possible and impossible objects that were encoded semantically or globally. Participants' performance was transformed into estimates of conscious and unconscious influences on memory via the Process Dissociation Procedure (PDP). Five major findings were obtained. First, developmental differences were observed in the relative strength of conscious and unconscious influences on memory such that conscious influences were stronger for younger than older adults, whereas unconscious influences were stronger for older than younger adults. Second, unconscious influences on memory were demonstrated for possible and impossible objects. Third, unconscious influences on memory were obtained for objects that were encoded in both a global and a semantic fashion. Fourth, age-related differences in conscious and unconscious influences on memory were unaffected by object type. Fifth, estimates of conscious and unconscious influences on memory were unrelated to scores on psychometric measures of visual-spatial ability: Primary Mental Ability-Space (PMA-Space) and Benton Facial Recognition Task (BFRT). Collectively, these findings have implications for our understanding of the relative strength of conscious and unconscious memory processes in younger and older adults as well as the different types of unconscious memory processes that are recruited by the PDP in comparison to the traditional priming methodology.     

Adult age differences in the implicit and explicit components of top-down attentional guidance during visual search

Two experiments investigated adult age differences in the explicit (knowledge-based) and implicit (repetition priming) components of top-down attentional guidance during discrimination of a target singleton. Experiment 1 demonstrated an additional contribution of explicit top-down attention, relative to the implicit effect of repetition priming, which was similar in magnitude for younger and older adults. Experiment 2 examined repetition priming of target activation and distractor inhibition independently. The additional contribution of explicit top-down attention, relative to the repetition priming of distractor inhibition, was greater for older adults than for younger adults. The results suggest that some forms of top-down attentional control are preserved as a function of adult age and may operate in a compensatory manner.     

Age and active navigation effects on episodic memory: A virtual reality study

We investigated the navigation‐related age effects on learning, proactive interference semantic clustering, recognition hits, and false recognitions in a naturalistic situation using a virtual apartment‐based task. We also examined the neuropsychological correlates (executive functioning [EF] and episodic memory) of navigation‐related age effects on memory. Younger and older adults either actively navigated or passively followed the computer‐guided tour of an apartment. The results indicated that active navigation increased recognition hits compared with passive navigation, but it did not influence other memory measures (learning, proactive interference, and semantic clustering) to a similar extent in either age group. Furthermore, active navigation helped to reduce false recognitions in younger adults but increased those made by older adults. This differential effect of active navigation for younger and older adults was accounted for by EF score. Like for the subject‐performed task effects, the effects from the navigation manipulation were well accounted for by item‐specific/relational processing distinction, and they were also consistent with a source monitoring deficit in older adults.     

Age-related differences in lexical access, spreading activation, and simple pronunciation

An experiment was conducted to address age-related differences in lexical access, spreading activation, and pronunciation. Both young and older adults participated in a delayed pronunciation task to trace the time course of lexical access and a semantic priming task to trace the time course of spreading activation. In the delayed pronunciation task, subjects were presented a word and then, after varying delays, were presented a cue to pronounce the word aloud. Older adults benefited considerably more from the preexposure to the word than did the younger adults, suggesting an age-related difference in lexical access time. In the semantic priming pronunciation task, semantic relatedness (related vs. neutral), strength of the relationship (high vs. low), and prime-target stimulus onset asynchrony (200 ms, 350 ms, 500 ms, 650 ms, and 800 ms) were factorially crossed with age to investigate age-related differences in the buildup of semantic activation across time. The results from this task indicated that the activation pattern of the older adults closely mimicked that of the younger adults. Finally, the results of both tasks indicated that older adults were slower at both their onset to pronounce and their actual production durations (i.e., from onset to offset) in the pronunciation task. The results were interpreted as suggesting that input and output processes are slowed with age, but that the basic retrieval mechanism of spreading activation is spared by age.     

Semantic versus phonological false recognition in aging and Alzheimer's disease

Patients with Alzheimer's disease (AD) have been found to exhibit lower levels of false recognition of semantic associates compared with healthy older adults. Because these patients may show impaired performance of episodic and semantic memory tasks, this finding could be explained by deficits in episodic memory, semantic memory, or both. The authors adapted a paradigm for comparison of semantic versus phonological false recognition. They found that: (a) patients with AD exhibited lower levels of corrected false recognition of semantic, phonological, and hybrid (mixed semantic and phonological) lists than older adults, and (b) patients with AD showed very similar levels of false recognition for all list types. These results suggest that only episodic memory deficits are necessary to explain the lower level of false recognition of semantic associates observed in patients with AD when compared to older adults. Additionally, (c) older adults showed greater levels of semantic, phonological, and hybrid false recognition than younger adults, extending previous false recognition research of semantically related words and categorized colored photographs to phonologically related words.