The importance of word-initial phonology: error patterns in prolonged naming efforts by aphasic patients.

Whether multiple conscious efforts at word search bring a subject closer to an elusive word and to eventual successful retrieval remains a subject of debate. Previous work with normal participants has shown that multiple attempts eventuating in correct retrieval are not usually associated with a systematic progression toward target word phonology in the intervening attempts. In this study we analyzed the naming errors produced by 30 aphasic patients who had received the Boston Naming Test. The analyses were designed to elucidate the characteristics of responses that led to eventual success. Our data showed that among aphasics, as with normal subjects, the presence of target-initial phonology in the subject's first response was the most important predictor of correct retrieval. Moreover, progression towards target phonology in the course of multiple attempts was unrelated to eventual correct retrieval.

Age and rate of activation in semantic memory.

Two word-primed picture-naming experiments were carried out to test the hypothesis that rate of activation in semantic memory is slower for older adults than for young adults. The presence of priming effects, both positive and negative, was taken as evidence of activation. In Experiment 1 there was no age difference in the time of onset of either facilitation or inhibition by primes. A computer simulation, based on a simple connectionist model, showed that slower processing would have only a minimal effect on the time of onset of priming effects under the assumptions of the model; however, offset of inhibition by primes would be delayed if processing rate were reduced. In Experiment 2 older adults showed inhibition by primes over a longer interval than did young adults, which was taken as evidence that the general slowing associated with aging extends to the transmission of activation at the earliest levels of cognitive processing.

Age and semantic inhibition in word retrieval.

An experiment to identify the source of age-related inhibition by semantically related primes in a word-retrieval paradigm is reported. Stimuli were definitions of target words, and responses were names of the target words that were defined. It has been shown previously that in this paradigm older adults are differentially inhibited by semantically related primes (Bowles & Poon, 1985a). The present experiment was designed to test the hypothesis that the additional inhibition by semantically related primes resulted from a decision strategy adopted by older adults when the primes themselves were sometimes correct target words. When the correct prime condition was eliminated in the present experiment, response times were statistically the same for semantically related and unrelated conditions for both older and younger adults. This suggests that the inhibition was due to additional decision processing performed by older adults rather than to longer retrieval processing in the presence of semantically related primes.

Age and context effects in lexical decision: an age by context interaction.

The present experiment demonstrates greater priming effects in a lexical decision task for older adults than for younger adults. Thirty-six older adults and thirty-six younger adults participated in a lexical decision experiment in which primes were category names and related targets were category exemplars that varied in category dominance. This manipulation of category dominance was intended to limit the predictability of target words based on prime words. Results showed that older adults had significantly greater priming effects than did younger adults. This outcome represents a departure from most studies of age effects on priming in lexical decision. It is suggested that older adults make greater use of context than younger adults when the context is of limited predictive value.

Naming errors in healthy aging and dementia of the Alzheimer type.

Naming errors were analyzed for healthy younger and older adults and patients with a diagnosis of senile dementia of the Alzheimer type (SDAT). Three types of errors were identified, varying in relatedness to the target word: near synonyms; semantically related naming errors; and unrelated naming errors. Older adults made relatively more related errors than did younger adults. SDAT patients were distinguished by the number of unrelated responses given. In addition, SDAT patients who scored within the normal range were identified by the high number of response attempts relative to the number of initial errors. We suggest that error patterns on naming tasks may potentially serve as clinical markers to distinguish healthy older persons with mild naming disorders from patients with SDAT.

Effects of priming in word retrieval.

Three studies were carried out to investigate orthographic and semantic priming effects in word retrieval. In this paradigm a prime is presented prior to the definition of a target word. The task is to produce the target word. We view the process of word retrieval as requiring access from a conceptually organized semantic network to an orthographically and phonemically organized lexical network. Primes that were orthographically (and phonemically) related to the target words were found to facilitate word retrieval. Both semantically related and unrelated primes inhibited word retrieval. Inhibition from both of these sources is attributed in part to the orthographic unrelatedness of these primes. This explanation is shown to be consistent with data from several other word retrieval studies (Brown, 1979; Roediger, Neely, & Blaxton, 1983). The word retrieval task is contrasted with the lexical decision task. It is suggested that the differential effects of orthographic and semantic priming in word retrieval and lexical decision are due to differences in retrieval processing between the two tasks.

Aging and retrieval of words in semantic memory.

Twenty-four young and 24 old adults participated in a lexical decision task (Study 1) in which they judged whether letter strings were words. No age differences were found in either accuracy or response latency. In Study 2 18 young and 18 old adults participated in a word retrieval study in which the stimulus was the definition of a target word and the task was to name the word that was defined. Younger adults were superior in word retrieval as measured by both number of successful retrievals and response latency. The discrepancy between the two sets of results is attributed to differences in retrieval requirements, which are interpreted within the framework of a two-component model of semantic memory. It is suggested that older adults have a specific deficit in accessing word-name information in an orthographically organized lexical network given stimulus information that is conceptual rather than orthographic.

On subject selection in cognitive aging research.

This paper surveys the recent practices of subject selection in cognitive aging research and provides examples of how the magnitude of age differences in the overall population could be under- or over-estimated given different sample distributions of gender, health, education and intellectual functioning. Some guidelines are suggested for consideration in future research.

On the use of word association norms in aging research.

The word associations of young, middle-aged, and older adults were compared to cohort matched normative word associations. Cohort differences in most common response were observed for a subset of stimulus words which did not have strong primary responses in the norms. For those stimulus words assumed to be free of cohort differences, there were no significant differences between the three age groups in amount of agreement with the normative responses. It is concluded that standard word association norms are as reliable for older individuals as for the young provided that words with strong associates are selected.

An analysis of the effect of aging on recognition memory.

The effect of aging on recognition memory processing is analyzed in terms of a stimulus-sampling model of recognition memory with parameters representing encoding effectiveness and stimulus overlap or interference. A standard study-test paradigm with a 2-alternative-forced-choice test was used with older and younger adults. While no significant difference in accuracy between groups was observed, it was found that the distribution of recognition scores for older adults was bimodal with an upper mode which did not differ from the younger group and a lower mode representing a large decrement in performance. For those adults who showed recognition deficity with aging, analysis in terms of the model revealed reduced encoding effectiveness. Recognition performance of the older adults was strongly related to verbal ability as measured by the WAIS vocabulary subtest. Disparate results of recognition studies in the aging literature are discussed in terms of variations in verbal ability among the groups studied.

The effect of age on speed of lexical access.

The present study concerns the effect of aging on speed of lexical access. Normative word-frequency was manipulated in a lexical decision task with older and younger adults. Three methods of comparing processing time in the lexical access stage across age groups were evaluated: the subtraction method, the analysis of covariance, and the additive-factor method. The adequacy of the subtraction method was questioned because of the difficulty of finding a control task identical to the experimental task in all processing stages except lexical access. The analysis of covariance was considered to be inconclusive in this kind of application because of the correlation between the covariate and the independent variable, age. The additive-factor method appeared to be a viable alternative to these two analyses. Within this framework, the lack of an interaction between the two variables, age and word-frequency, indicates that the factors affected different stages of processing. Since word-frequency has been shown to affect the lexical access stage, the present result was taken to suggest that aging does not affect speed of lexical access.