Biomedical subjects

T A Salthouse

Publications and source records attributed to T A Salthouse.

At least 19 recordsLinked to original sources

PubMed1996

The processing-speed theory of adult age differences in cognition.

A theory is proposed to account for some of the age-related differences reported in measures of Type A or fluid cognition. The central hypothesis in the theory is that increased age in adulthood is associated with a decrease in the speed with which many processing operations can be executed and that this reduction in speed leads to impairments in cognitive functioning because of what are termed the limited time mechanism and the simultaneity mechanism. That is, cognitive performance is degraded when processing is slow because relevant operations cannot be successfully executed (limited time) and because the products of early processing may no longer be available when later processing is complete (simultaneity). Several types of evidence, such as the discovery of considerable shared age-related variance across various measures of speed and large attenuation of the age-related influences on cognitive measures after statistical control of measures of speed, are consistent with this theory.

Adolescent↗

PubMed1996

General and specific speed mediation of adult age differences in memory.

The proposal that age-related differences in some measures of speed of performance may not be independent of the age-related differences in other measures of speed of performance has been associated with considerable controversy. Because converging evidence can often resolve this type of controversy, correlation-based procedures are proposed to distinguish general (or common) and specific (or unique) age-related influences on measures of speeded performance. Results from three earlier studies and from a new study suggest that a large proportion of the age-related variance in a wide range of speed measures is shared and is not distinct. Furthermore, the common or general speed factor appears to play an important role in the mediation of age-related differences in memory.

Adolescent↗

PubMed1996

Where in an ordered sequence of variables do independent age-related effects occur?

A series of regression analyses was conducted to determine which variables in an ordered sequence had significant age-related effects after control of the immediately preceding variable in the sequence. Independent age-related effects in these types of analyses are particularly interesting because they represent age-related influences that are not mediated through earlier variables. A total of 56 analyses are reported with ordered variables representing: (a) successive trials or sessions in learning; (b) progressively more intervening events during the retention interval of a memory task; (c) successively longer stimulus presentation durations; and (d) increased processing complexity. In most of the analyses a very large proportion of the age-related effects on later variables was found to be mediated through earlier variables in the sequence.

Adult↗

PubMed1995

Interrelations of age, health, and speed.

Latent construct structural equation modeling of the relations among age, self-rated health, and speed was conducted with two samples, each containing 372 adults between 18 and 87 years of age. The major results were confirmed in both samples. Self-rated health, sensory-motor speed, perceptual speed, and reaction time speed all decreased as age increased, but health only partially mediated the relationship between age and speed. There were direct effects of age on all types of speed in addition to the indirect effects of age on speed through the self-rated health measures, and there were direct effects of age on perceptual speed in addition to the indirect effects through sensory-motor speed.

Adolescent↗

PubMed1995

Differential age-related influences on memory for verbal-symbolic information and visual-spatial information?

Adults from a wide range of ages were administered parallel versions of three memory tasks designed to involve verbal-symbolic information or visual-spatial information. Several analytical procedures were used to determine whether there were selective age-related effects on measures reflecting spatial information processing compared to those reflecting verbal-symbolic information processing. The results provided little support for this hypothesis and instead were consistent with the existence of a common age-related factor that contributes to the age differences in many cognitive measures.

Adolescent↗

PubMed1995

Aging, inhibition, working memory, and speed.

An implication of the hypothesis that failures of inhibition contribution to adult age differences in working memory (Hasher & Zacks, 1988) is that statistical control of measures of inhibition should reduce the age-related effects on working memory. This implication was tested in a study in which interference measures from three variants of a Stroop task served as the measures of inhibition. Although the age-related variance in measures of working memory was substantially reduced after control of the interference measures, the degree of attenuation was at least as large when speed measures from other tasks were controlled. Furthermore, additional analysis revealed that speed measures from tasks requiring oral, written, and keypress responses shared large proportions of their age-related variance. It was suggested that age-related influences on specific processes, such as inhibition, cannot be accurately assessed unless the contributions of more general age-related influences are taken into consideration.

Adult↗

PubMed1995

Aging of attention: does the ability to divide decline?

Previous research has yielded conflicting results regarding the relationship between adult age and the ability to divide attention between two concurrent tasks. At least some of the inconsistency is probably attributable to methodological variations, such as the manner in which divided-attention ability has been assessed, how single-task performance has been considered, and the degree of control over relative emphasis placed on each task. Two experiments employing procedures sensitive to these concerns were conducted in which a speeded decision task was performed during the retention interval of a letter-memory task. The results of both experiments indicated that there were relatively few age-related influences on dual-task performance vis-à-vis those on single-task performance.

Adult↗

PubMed1995

Analyses of adult age differences in associative learning.

Data from a recent project concerned with adult age differences in associative learning were reanalyzed to identify the processes involved in the age-related differences in trial-by-trial performance in this task. A measure reflecting the failure to retain feedback relevant to one's previous response accounted for a large proportion of the age differences in the early trials of associative learning. The speed with which individuals completed simple processing operations also contributed to the age differences both in measures of accuracy (percentage correct) and in measures of feedback retention.

Adolescent↗

PubMed1995

Selective influences of age and speed on associative memory.

Data from three studies involving a continuous paired associates task performed by adults of different ages were analyzed in an attempt to identify how processing speed might mediate age-related differences in associative memory. Age differences were found in measures postulated to represent encoding and consolidation processes, but not in a measure presumed to reflect rate of forgetting. It is suggested that increased age is associated with a reduction in the speed of executing processes concerned with establishing a stable internal representation, but not with an alteration in the rate at which encoded information is lost as a function of time or subsequent processing.

Adult↗

PubMed1994

Processing speed as a mental capacity.

Throughout the lifespan, there are pronounced age differences in speed of processing, differences that are consistently related to performance on measures of higher-order cognition. In this article, we examine domain-specific and global explanations of these age differences in processing speed; we conclude that although experience can play a role in age differences in speed, there is also evidence that a general mechanism limits speeded performance. We also review research that shows the influence of processing speed on the quality of performance on nonspeeded tasks such as reasoning and memory. We suggest that speed of processing should be viewed as a fundamental part of the architecture of the cognitive system as it develops across the entire lifespan.

Adolescent↗

PubMed1994

Interpretation of differential deficits: the case of aging and mental arithmetic.

A fundamental issue in research on individual differences is the type of evidence sufficient to justify an inference of selective or distinct deficits in relevant theoretical processes. It is proposed that an important consideration is the extent to which the individual differences in 1 variable are independent of those in another variable. Specifically, the suggestion presented here is that a strong conclusion of selective impairment requires evidence that there is significant group-related variance in 1 variable after the variance in the other relevant variable is controlled. Furthermore, an inference that the groups are equivalent on a particular theoretical process requires evidence that the variable presumed to reflect that process has sufficient unique variance to justify the claim that a distinct process is being assessed. The proposed methods are illustrated with two studies comparing adults of different ages in mental arithmetic tasks.

Adult↗

PubMed1994

Aging associations: influence of speed on adult age differences in associative learning.

Two studies, involving a total of nearly 500 Ss, were conducted to determine the mechanisms by which processing speed contributes to the relations between adult age and associative learning. Results of both studies indicated that increased age was related to poorer associative learning largely because of a failure to retain information about previously correct responses. This in turn was related to the effectiveness of encoding briefly presented information in an associative memory task, which was related to measures of processing speed. It is therefore suggested that age-related decreases in speed of processing lead to less effective encoding or elaboration, which results in a fragile representation that is easily disrupted by subsequent processing.

Adult↗

PubMed1993

Speed and knowledge as determinants of adult age differences in verbal tasks.

Two studies were conducted to determine the relative importance of processing speed and knowledge as predictors of performance in simple verbal tasks within samples of young and old adults. Eight different criterion tasks were investigated, and performance on each was found to be significantly related both to speed of processing and to quantity of word knowledge. It was also discovered that although young adults were faster than old adults and that old adults were equal or superior to young adults in relevant knowledge, the same regression equations could be used to predict criterion performance in both groups. These results therefore suggest that any age-related compensation that exists in these tasks is rather weak, in the sense that speed and knowledge appear to have the same importance in young and old adults, and only the average levels of the predictors differ as a function of age.

Adult↗

PubMed1993

Influence of task-specific processing speed on age differences in memory.

Two studies were conducted to investigate the aspect(s) of processing involved in the hypothesized speed mediation of adult age differences in memory. Both studies involved a serial memory task in which information was to be recalled either in the original order of presentation, or in a reordered sequence. Results from both studies indicated that task-specific processing durations were slower among older adults than among young adults, but that the attenuation of the age-related variance in memory was nearly as great after statistical control of a task-independent speed measure as after control of task-specific speed measures. These findings are consistent with the hypothesis that a substantial proportion of the adult age-related differences in memory is associated with a decrease with increased age in the speed of executing many cognitive processes, and not simply the speed of one or two specific processes.

Adolescent↗

PubMed1993

Attentional blocks are not responsible for age-related slowing.

Reaction time (RT) data in two tasks from a total of 784 adults between 18 and 87 years of age were analyzed to determine the relation between age and parameters of the intra-individual RT distribution. Although the absolute magnitude of the age differences was greatest for the slowest RTs in each individual's RT distribution, there was little or no independent age-related variance in the slowest RTs after controlling for the variance in the fastest RTs. Furthermore, the relation between RT and measures of motor speed, perceptual speed, working memory, and accuracy in several cognitive tasks was of nearly the same magnitude when only the fastest responses were considered as when both fast and slow responses were considered. These results imply that age-related slowing is associated with a shift (and expansion) in the entire RT distribution, and is not attributable to a selective influence on the individual's slowest responses.

Adult↗

PubMed1993

Influence of working memory on adult age differences in matrix reasoning.

The four studies reported in this article, involving a total of 401 adults ranging between 18 and 80 years of age, were designed to investigate how working memory might mediate adult age differences in matrix reasoning tasks such as the Raven's Progressive Matrices Test. Evidence of this medication is available in the finding that statistical control of an index of working memory reduces the age-related variance in matrix reasoning performance by approximately 70 per cent. Because the age differences were nearly constant across items of varying difficulty, it was concluded that the factors responsible for variation in item difficulty were distinct from those responsible for the age differences. However, young adults were found to be more accurate than older adults at recognizing information presented earlier in the matrix reasoning trial, thereby supporting the interpretation that working memory exerts its influence by contributing to the preservation of information during subsequent processing.

Adolescent↗

PubMed1993

Decomposing adult age differences in symbol arithmetic.

A componential analysis was conducted to determine the locus of adult age differences in symbol arithmetic. Measures of the duration of two proposed components, substitution of digits for symbols and the addition or subtraction of the digits resulting from these substitutions, were obtained from 52 young adults and 52 older adults. Tests of working memory, perceptual speed, motor speed, and associative learning were also administered to all subjects. The results were most consistent with an interpretation postulating that the speed of many different cognitive processes decreases with increased age. Considerable age-related variance remained in the measures of symbol arithmetic performance after statistical control of working memory and associative learning performance, casting doubt on alternative hypotheses of the source of age-related differences in this task.

Adolescent↗

PubMed1992

Influence of processing speed on adult age differences in working memory.

Two studies are reported in which adults ranging from 18 to 80 years of age performed tasks designed to measure working memory functioning and perceptual comparison speed. The results from both studies indicated that statistical control of the measures of perceptual comparison speed greatly attenuated the age-related variance in measures of working memory even when working memory was assessed under self-paced conditions. Additional results in the second study supported the hypothesis that the speed influence was manifested in the rate of activating information rather than in the rate at which it was lost as a function of time or other processing.

Adolescent↗