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Biomedical subjects

C L McEvoy

Publications and source records attributed to C L McEvoy.

16 recordsLinked to original sources
PubMed2000

Is APOE--epsilon4 a risk factor for cognitive impairment in normal aging?

OBJECTIVES: To examine the relationship between APOE genotype and cognitive functioning in normal aging, and to determine whether this relationship was moderated by age or the presence of a number of disease conditions, including cardiovascular disease and diabetes. METHODS: The sample was drawn from the Charlotte County Healthy Aging Study, a community-based, cross-sectional study of randomly selected older adults in Charlotte County, FL. A total of 413 older adults (mean age = 72.90 years) were examined in the current study. Participants completed tasks that indexed a variety of dimensions of cognitive functioning, including episodic memory, implicit memory, psychomotor speed, and attention. In addition, participants provided self-reported and objective indices of health status and were genotyped for APOE. RESULTS: Mean-level results indicated that groups with and without the APOE-epsilon4 allele performed similarly on all domains of cognitive functioning. Significant age group differences were observed in episodic memory, psychomotor speed, and attention but not implicit memory. Significant gender differences were present for episodic memory and the Stroop test. Analyses also indicated that participants' age did not exert an impact on the relationship between APOE-epsilon4 and cognitive functioning. Further, the presence of cardiovascular disease or diabetes did little to moderate the relationship between APOE-epsilon4 and cognition. CONCLUSIONS: The authors found no evidence for a relationship between presence of the APOE-epsilon4 allele and cognitive functioning. Further, age or the presence of a number of chronic conditions did not significantly moderate the effect of APOE genotype on cognitive performance. These results indicate that the presence of the epsilon4 allele is not a risk factor for cognitive impairment in normal aging.

Age Factors↗
PubMed2000

What is this thing called frequency?

When researchers are interested in the influence of long-term knowledge on performance, printed word frequency is typically the variable of choice. Despite this preference, we know little about what frequency norms measure. They ostensibly index how often and how recently words are experienced, but words appear in context, so frequency potentially reflects an influence of connections with other words. This paper presents the results of a large free association study as well as the results of experiments designed to evaluate the hypothesis that common words have stronger connections to other words. The norms indicate that common words tend to be more concrete but they do not appear to have more associates, stronger associates, or more connections among their associates. Two extralist cued recall experiments showed that, with other attributes being equal, high- and low-frequency words were equally effective as test cues. These results suggest that frequency does not achieve its effects because of stronger or greater numbers of connections to other words, as implied in SAM. Other results indicated that common words have more connections from other words, including their associates, and that free association provides a valid index of associative strength.

Adult↗
PubMed2000

What is free association and what does it measure?

This paper reports the results of a study of free association in which participants were asked to produce the first two words to come to mind. The findings were used to estimate the reliability of indices of strength and set size for different types of items and to model free association as a retrieval task. When confined to first responses, reliability was generally high for both indices, particularly for words with smaller sets of associates and stronger primaries. When second responses were included, reliability declined. A second response added new but weak items to the set, and, when the primary associate was not produced on the first opportunity, it tended not to be produced on the second. Relative to when multiple responses are requested, first-response free association provides more reliable indices of the relative strength and set size for a word's strongest associates. A model of free association assuming that a strength distribution underlies each response provided a good fit to the data.

Free Association↗
PubMed1999

What is the connection between true and false memories? The differential roles of interitem associations in recall and recognition.

Veridical memory for presented list words and false memory for nonpresented but related items were tested using the Deese/Roediger and McDermott paradigm. The strength and density of preexisting connections among the list words, and from the list words to the critical items, were manipulated. The likelihood of producing false memories in free recall varied with the strength of connections from the list words to the critical items but was inversely related to the density of the interconnections among the list words. In contrast, veridical recall of list words was positively related to the density of the interconnections. A final recognition test showed that both false and veridical memories were more likely when the list words were more densely interconnected. The results are discussed in terms of an associative model of memory, Processing Implicit and Explicit Representations (PIER 2) that describes the influence of implicitly activated preexisting information on memory performance.

Cognition↗
PubMed1995

Age effects in cued recall: sources from implicit and explicit memory.

In 2 experiments, young and old adults were compared on cued recall using direct and indirect test instructions. Participants studied words under an incidental orienting task of rating each word for concreteness. Test cues were meaningfully related to the targets, and participants used them either to recall the studied word (direct test) or to generate a related word (indirect test). Target words and test cues varied in the number of associates linked to them prior to the laboratory experience, and effects of the size of the sets of associates were used as indicators of implicit memory search. Age differences were observed in the effects of target and cue set size as well as in the effects of type of test instruction.

Adolescent↗
PubMed1992

Implicit processing in the cued recall of young and old adults.

Two cued recall experiments were reported in which younger and older subjects studied target words varying in number of preexperimental associates. In Experiment 1, targets were studied in either the absence or presence of meaning-related context cues, with recall always prompted by the cues. In the absence of context, words with smaller sets of associates were easier to recall than those with larger sets, but this effect was reduced for older subjects. The presence of a study context cue facilitated recall and eliminated the effect of associative set size for both ages. In Experiment 2, targets were studied and tested in the presence of unrelated words. In this situation, words with smaller sets of associates were less likely to be recalled than words with larger sets; again the effect was reduced for older subjects. The results are interpreted as an age decrement in processing implicitly activated information.

Adult↗
PubMed1992

Processing implicit and explicit representations.

This article summarizes the results of a 15-year research program dedicated to understanding how implicitly activated memories affect remembering and proposes a model for describing such influences. Implicit memories are manipulated by varying the number of associates preexperimentally linked to test cues or to studied words. Assumptions of the model specify when implicit memories of various types are likely to contribute to performance in various tasks. The main assumptions are that encoding involves both explicit and implicit processing components and that these components provide mutually exclusive sources of information during testing. Experiments designed to evaluate the exclusivity assumption are reported, and implications of the findings for several theoretical frameworks are discussed.

Attention↗
PubMed1990

Encoding context and retrieval conditions as determinants of the effects of natural category size.

Studying a familiar word activates its associates in long-term memory. In the present experiments we manipulated the number of associates activated by words studied in the presence of unrelated context words, meaningfully related context words, or in the absence of modifying context words. Memory was tested by either cued or free recall. The results showed that the number of directly activated associates can facilitate, have no effect, or disrupt recall for studied words. The direction and magnitude of the effects of number of activated associates is shown to be determined by the encoding/retrieval context. Implications for the distinction between episodic and semantic memory are discussed.

Association↗
PubMed1990

Aging and the stability of activation and sampling in cued recall.

Age effects in cued recall were investigated as a function of activation and sampling of preexisting associates of the test cue. Young adults, community-dwelling elderly, and elderly patients studied lists of unrelated words and were tested with extralist cues. Preexperimental strength between test cues and studied words was manipulated to discern differences in activation, and normative size of the set of associates was manipulated to discern differences in sampling. Test delay and prior testing were also manipulated in Experiment 1. Although large age effects were found with phonemic and taxonomic test cues, young and older subjects showed comparable effects of strength and set size, suggesting that age effects were not due to activation and sampling differences. Test delay and prior testing also had comparable effects. Implications for age effects in episodic cued recall are discussed.

Adolescent↗
PubMed1990

Selective access in cued recall: the roles of retrieval cues and domains of encoding.

The purpose of these experiments was to determine whether retrieval access in cued recall can be selectively restricted to a single domain of encoding when information has been encoded within two domains as different as word sound and word meaning. In Experiment 1, the subjects studied pairs of rhyming words differing in rhyme set size under verbal-repetition or interactive-imagery instructions. Recall was cued with study-context rhymes, with extralist rhymes, or with extralist associates. The results indicated that rhyme set size and instructional effects were found no matter how recall was cued, indicating that both domains of encoding were always accessed. In Experiment 2, potential effects of study time and overt naming of the test cues were explored. These results indicated that both domains of encoding were accessed, except when long study times were available and subjects did not have to name the rhyme test cues. Rhyme set-size effects were eliminated under these conditions, suggesting that selective access to encoded meaning is possible in cued recall. Retrieval access in this task appears to be more controlled by domains of encoding than by information directly available in the cue, and access to encoded information can be restricted to a single domain.

Adult↗
PubMed1989

Prior knowledge: the effects of natural category size on memory for implicitly encoded concepts.

Studying a familiar word activates its associates, and these associates affect the likelihood of recalling the studied word in a cued recall task. These experiments examined variables that normally affect memory for the studied word to determine if they have similar effects on memory for the word's associates. Memory for associates was tested by cued recall (Experiments 1-3) or by recognition (Experiments 4-5), with the number and strength of the associates varied in all experiments. In different experiments, test instructions (direct-indirect), distractor tasks, lag, and amount of practice were manipulated. Provided that subjects were not distracted prior to test, the probability of recalling associates of the studied word decreased with the number of associates activated and with their strength under all conditions. The strength of the associates but not their number affected recognition. In general, variables that affected recall and recognition of studied words had parallel effects on their associates.

Adult↗
PubMed1988

Automatic and strategic processes in picture naming.

Prior presentation of related priming stimuli can facilitate responding to subsequent targets. However, recent research has demonstrated that inhibition effects can be produced by related primes when some of the primes in the testing sequence directly name their targets. This study used a picture-naming task, manipulating strength of relation between the prime word and the target picture, and the presence of identical primes in the testing sequence. Related primes facilitated naming when identical primes were absent, but not when they were present, whereas the strength effect did not vary as a function of identical-prime presence. A second experiment replicated the strength effect and showed that it was not affected by the presence or absence of primary associates in the testing sequence. A comparison-strategy explanation of the inhibition effect is proposed, in which the strategy is superimposed on an automatic activation of related information.

Adult↗
PubMed1988

Lexical and semantic search in cued recall, fragment completion, perceptual identification, and recognition.

Search processes in word-stem cued recall, fragment completion, perceptual identification, and recognition are contrasted. These retention tests involve letters as cues, but the lexical characteristics of these cues vary considerably. In word-stem cued recall, ending letters are presented as recall cues for studied targets (e.g., ONEY as a cue for HONEY). In fragment completion, the test cues consist of letters and spaces (e.g., HO__Y); in perceptual identification, they consist of letter features that survive the mask; and in recognition, they consist of all the letters of the studied word (e.g., HONEY). These differences in retention tests and lexical characteristics were evaluated by manipulating three variables with known effects in cued recall: (a) the presence of study context words emphasizing lexical information, (b) lexical set size corresponding to the number of words that fit the letter cue, and (c) meaning set size corresponding to the number of meaningful associates linked to the studied targets. The results indicated that (a) the presence of study contexts emphasizing lexical information reduced accuracy and response time equally in all tasks, (b) larger lexical set sizes reduced accuracy and response time in all tasks except recognition, and (c) larger meaning set size reduced accuracy in cued recall but not in the other tasks. Lexical search appears to be a significant component process in word-stem cued recall, fragment completion, and identification. Searching through meaning-related concepts encoded during study is a significant component process only in cued recall.

Adult↗
PubMedDate not supplied

Mediated priming in younger and older adults.

This paper reports the result of a lexical decision experiment in which the primes were either directly related to their targets, mediated, or unrelated. Mediated primes are indirectly related to their targets through a single connecting link (e.g., PASTURE-COW-MILK). Older and younger adult subjects responded to each letter string in a continuous lexical decision task, deciding whether each string was a word or a nonword. The results indicated that both younger and older subjects benefited from the mediated primes, as well as from the directly related primes. The results are discussed in relation to issues of age changes in processing speed.

Adult↗