Timothy Salthouse - US grants

Very little empirical data are available on the capabilities of older adults relative to young adults in activities in which they have had many thousands of hours of experience at home or on the job. Since most laboratory tasks are deliberately designed to be somewhat abstract and unlike real-world activities, the current research literature provides very little basis for making predictions about the occupational suitability of adults of varying ages. The present project attempts to bridge the gap between laboratory and occupational activities by examining adult age differences in a variety of tasks designed to measure components of typing behavior. Preliminary data have already revealed that although typists between 20 and 70 years of age exhibit "typical" age-related declines in the efficiency of laboratory measures of perceptual-motor performance, there is no age trend in the efficiency of the commonly performed, and highly overlearned, activity of typing. Finer analyses of the data also indicate that a mechanism apparently used by the older typists in normal typing to circumvent a slowing of elementary perceptual-motor processes is greater anticipation or preparation of forthcoming keystrokes. Two analytical studies in the current project are planned to confirm and extend this finding, and also to explore other compensatory mechanisms that might be employed by older typists. A third study will examine personnel records and attempt to obtain current timed typing scores of employees for whom earlier typing scores are still available. It is hoped that in this manner any longitudinal age changes in typing proficiency that occur could be detected without the expense and delay of a true longitudinal study. The long-term objectives of the project are: a) to investigate age trends in highly-practiced activities to determine whether age-related declines in component processes can be compensated for by extensive experience; and b) to provide a detailed description of the nature of any compensatory mechanisms employed by older adults.

The present application proposes a theoretical interpretation of age differences in cognitive processes based on one of the best-documented empirical results in the psychological literature - a progressive decrease in speed of behavior with increasing age. Most if not all of this slowing-with-age phenomenon is determined by central rather than peripheral factors, and therefore it is likely to share causes with, and have consequences for, other cognitive processes. Unlike other theoretical speculations, the processing rate interpretation applies to a variety of cognitive activities ranging from simple reaction time, to memory, to decision-making. Furthermore, because of the central status of temporal variables in the perspective, there is greater opportunity for cross-disciplinary interaction and corroboration since time is as meaningful a measure in physiology as in psychology. Four broad approaches to age differences in processing rate and cognition will be pursued. One concerns a possible hypothesis (neural noise) about the cause of the slower processing rate in older adults. A second deals with the problem of which temporal measure is most satisfactory as an estimate of internal rate of information processing. The third issue involves the nature of the quantitative expression relating performance time to adult age. And finally, a fourth approach to the general problem will explore the consequences of slower rates of processing on a number of cognitive tasks such as memory and comprehension. It is believed that this broad, multifaceted perspective will not only lead to substantive advances in the knowledge about causes of age differences in cognition, but the methodological skills and sophistication of the principal investigator will also be increased because of the wide variety of procedures and techniques that are to be employed.

Four series of studies are proposed to investigate the hypothesis that age-related impairments in reasoning and spatial abilities are attributable to a decrease with age in the rate of processing information. The first phase of the project is designed to examine the complexity effect phenomenon (i.e., the trend for the magnitude of the age differences to increase with the complexity of the task) in reasoning and spatial domains. Experiments in the second phase will determine whether, and if so by how much, older adults differ from young adults in the duration of component processes of prototypical reasoning and spatial ability tasks. The goal of the Phase 3 studies is to provide an empirical demonstration that variations in rate of processing can result in substantial differences in quality of performance. The final phase in the project is to construct a working computer simulation of two prototypical tasks to explore the possibility of reproducing the age differences in performance by manipulating only rate parameters in the simulation. The goal is to explore the feasibility of the proposal that reductions in the efficency of cognitive functioning associated with increased age are attributable to a slower rate of processing information Result from the proposed studies should not only contribute to greater understanding of reasons for adult age differences in cognition, but may also be useful in attempting to discover mechanisms by which health variables influence mental functioning.

occupations; aging;

Two sets of studies are proposed to investigate the hypothesis that age- related impairments in reasoning and spatial abilities are attributable to a decrease with age in certain aspects of working memory. One set of studies will attempt to identify which aspects of working memory are most influenced by increased age, and to determine the relationship between measures of memory obtained during the processing of on-going cognitive tasks and from tasks deliberately designed to assess memory functioning. the second set of studies will focus on the interrelations of age, working memory, and performance in reasoning and spatial tasks of cognitive functioning. A primary goal of both sets of studies is to specify how age-related limitations of working memory might contribute to lower levels of performance in prototypical cognitive tasks. Ultimately it is hoped that this research will indicate the specific mechanisms by which increased age, and potentially a variety of health-related conditions, influence an individuals's level of cognitive functioning.

Executive processes are frequently implicated as a factor contributing to age-related cognitive deficits, and to cognitive impairments associated with a variety of different diseases and neuropathological conditions. However, it is not yet known whether variables hypothesized to reflect executive processes represent a unitary dimension of individual differences, if and how executive processes are related to other types of cognitive variables, and to what extent age-related effects on different cognitive variables may be mediated by age- related effects on executive processes. These issues will be investigated in a series of studies involving samples of between 100 and 250 healthy adults between 18 and approximately 80 years of age. The initial age-comparative studies will focus on four aspects of executive processes (i.e., updating, time-sharing, and planning), with each young and old adult participant performing three tasks hypothesized to assess each executive process aspect. The goals of these studies are to examine the degree to which the three variables postulated to represent the same aspect of executive processes are correlated with one another, and hence may represent a unitary dimension of individual differences, and to investigate possible changes in the pattern of correlations, and reliabilities of the executive process variables, across two sessions of practice. The final study in the project will involve a total of about 250 healthy adults ranging from 18 to 80 years of age who will perform a battery of tasks designed to assess different aspects of executive processes and other types of cognitive functioning such as perceptual speed and working memory. A variety of correlation-based analyses, including structural equation models, will be used to evaluate the plausibility of hypotheses regarding the unitary or multiple nature of executive processes, relations of executive process variables to variables representing other types of cognition, and the level (i.e., specific to individual variables or common to many variables) at which age-related influences operate on executive process variables.

? DESCRIPTION (provided by applicant): This is an application to continue research originally started in 2001, and expanded into a longitudinal study, known as the Virginia Cognitive Aging Project (VCAP), in 2005. Over 2,300 adults 18 - 95 years old have now completed at least two longitudinal occasions, with an average of 2.7 occasions and an average time in study of 5.1 years. The research proposed in the next funding period will extend the investigation of short-term longitudinal change in a broad variety of cognitive measures, with particular emphasis on adults under the age of 80. Although previous studies have found little or no cognitive change in longitudinal comparisons involving young and middle-aged adults, this research employs three methodological innovations, variable retest intervals, measurement bursts at each occasion, and continuous recruitment of new participants, that help distinguish age effects from experience (retest) effects, and that increase sensitivity to detect change by taking into account normal short-term variability in performance. Among the primary questions to be investigated are when does normal age-related cognitive change begin, the degree to which changes in different cognitive variables are independent of one another at different periods in adulthood, the role of prior test experience on the direction and magnitude of cognitive change at different ages, the degree to which factors such as one's cognitive or physical lifestyle moderate the amount of age-related change in different cognitive abilities at various periods in adulthood, and how early can normal and pathological trajectories of cognitive aging be distinguished. Specific aims during the next grant period are to: (1) Expand the characterization of normal cognitive aging across the range from about 18 to 80 years old; (2) Extend the investigation of the role of experience effects on cognitive change; (3) Investigate the structure and nature of cognitive change across different levels of analysis and across a wide range of ages; and (4) Increase sensitivity of VCAP tests to detect early stages of cognitive pathology among VCAP participants.