Sandra Hale - US grants

The proposed research tests the broad claims of the information-loss model of age-related cognitive slowing proposed by Myerson, Hale, Wagstaff, Smith, and Poon (1990). The model assumes that a single factor, variations in the number of processing steps, is responsible for how response latencies are affected by task complexity, practice, fluctuations in individual performance, and shifts in the emphasis on speed versus accuracy. The model further assumes that a second factor, differences in information-processing efficiency, underlies differences in response latencies of older and younger adults. The interaction of these two factors determines the form of the relation between the latencies of older and younger adult. Establishing the relation between the latencies of older and younger adults will provide an important cognitive benchmark that can be used to determine when individual patterns of cognitive slowing are typical of healthy older adults and when such patterns are indicative of pathological changes. To study this relation, three series of experiments will examine the latencies of older and younger adults on a variety of cognitive tasks. The first series will manipulate practice and speed-accuracy tradeoff to test the hypothesis that the relation between older and younger adults' latencies remains invariant. The second series will examine individual subjects and fluctuations in their performances to test the hypothesis that information loss slows all cognitive processes in all individuals at all levels of performance. The final series will test for the existence of two cognitive domains, each with its own developmental trend with respect to cognitive slowing, and is designed to determine the factors responsible for information loss. In all three series, the predictions of the information-loss model will be compared with those of alternative models of global cognitive slowing, e.g., the multi-layered slowing model and the overhead model proposed by Cerella (1985; 1990).

The proposed research tests the broad claims of the information-loss model of age-related cognitive slowing proposed by Myerson, Hale, Wagstaff, Smith, and Poon (1990). The model assumes that a single factor, variations in the number of processing steps, is responsible for how response latencies are affected by task complexity, practice, fluctuations in individual performance, and shifts in the emphasis on speed versus accuracy. The model further assumes that a second factor, differences in information-processing efficiency, underlies differences in response latencies of older and younger adults. The interaction of these two factors determines the form of the relation between the latencies of older and younger adult. Establishing the relation between the latencies of older and younger adults will provide an important cognitive benchmark that can be used to determine when individual patterns of cognitive slowing are typical of healthy older adults and when such patterns are indicative of pathological changes. To study this relation, three series of experiments will examine the latencies of older and younger adults on a variety of cognitive tasks. The first series will manipulate practice and speed-accuracy tradeoff to test the hypothesis that the relation between older and younger adults' latencies remains invariant. The second series will examine individual subjects and fluctuations in their performances to test the hypothesis that information loss slows all cognitive processes in all individuals at all levels of performance. The final series will test for the existence of two cognitive domains, each with its own developmental trend with respect to cognitive slowing, and is designed to determine the factors responsible for information loss. In all three series, the predictions of the information-loss model will be compared with those of alternative models of global cognitive slowing, e.g., the multi-layered slowing model and the overhead model proposed by Cerella (1985; 1990).

The proposed research plan applies recent theoretical models to the variety of cognitive changes that characterize Dementia of the Alzheimer's Type (DAT). Healthy elderly adults exhibit Changes that appear similar to, but much milder than, those observed in DAT. In three studies, each examining performance on at least 12 tasks, subjects with DAT will be compared with both young and healthy elderly adults in order to address the question of whether cognitive changes in DAT represent exaggerated aging or unique pathology. Taken together, the three studies will generate precise information about the interrelations between many of the cognitive symptoms of this disease, focusing on the extent to which slowing in DAT is global or task-specific, and the consequences of slower processing for memory and cognition. Salthouse (e.g., 1991, 1992) has proposed a model in which the cognitive changes associated with normal aging form a cascade: A global decrease in processing speed leads to a decrease in working memory capacity that, in turn, causes a decline in higher cognitive abilities. The purposes of the first study are to test a model of cognitive changes in DAT that parallels Salthouse's account of normal aging and to explore the relations between speed, memory, and higher cognitive abilities. The second study will examine more closely the link between speed and memory. Baddeley (e.g., 1983, 1992) has proposed a three-component model in which working memory function depends upon two modality-specific slave systems controlled by a central executive. Like Salthouse, Baddeley has suggested that speed, more specifically articulation rate, is a major determinant of the capacity of working memory. In addition, Baddeley suggested that deficits in the central executive underlie working memory deficits in DAT. The second study will evaluate Baddeley's model and test his hypothesis concerning central executive deficits in DAT. In healthy elderly, the ability to process and remember lexical information is much better preserved than the ability to processing and remember nonlexical information (Myerson & Hale, 1993; Hale, Myerson, & Rhee, 1994), and the same appears to true in DAT. Although Baddeley's working memory model includes only one slave system for visuospatial information, recent research in cognitive neuroscience has identified separate neural processing streams specialized for perceiving and remembering objects and locations. The third study will examine whether object and location information are both more sensitive than lexical information to the effects of aging and DAT.

The proposed research plan applies recent theoretical models to the variety of cognitive changes that characterize Dementia of the Alzheimer's Type (DAT). Healthy elderly adults exhibit changes that appear similar to, but much milder than, those observed in DAT. In three studies, each examining performance on at least 12 tasks, subjects with DAT will be compared with both young and healthy elderly adults in order to address the question of whether cognitive changes in DAT represent exaggerated aging or unique pathology. Taken together, the three studies will generate precise information about the interrelations between many of the cognitive symptoms of this disease, focusing on the extent to which slowing in DAT is global or task-specific, and the consequences of slower processing for memory and cognition. Salthouse has proposed a model in which the cognitive changes associated with normal aging form a cascade: A global decrease in processing speed leads to a decrease in working memory capacity that, in turn, causes a decline in higher cognitive abilities. The purposes of the first study are to test a model of cognitive changes in DAT that parallels Salthouse's account of normal aging and to explore the relations between speed, memory, and higher cognitive abilities. The second study will examine more closely the link between speed and memory. Baddeley has proposed a three-component model in which working memory function depends upon two modality-specific slave systems controlled by a central executive. Like Salthouse, Baddeley has suggested that speed, more specifically articulation rate, is a major determinant of the capacity of working memory. In addition, Baddeley suggested that deficits in the central executive underlie working memory deficits in DAT. The second study will evaluate Baddeley's model and test his hypothesis concerning central executive deficits in DAT. In healthy elderly, the ability to process and remember lexical information is much better preserved than the ability to process and remember nonlexical information, and the same appears to be true in DAT. Although Baddeley's working memory model includes only one slave system for visuospatial information, recent research in cognitive neuroscience has identified separate neural processing streams specialized for perceiving and remembering objects and locations. The third study will examine whether object and location information are both more sensitive than lexical information to the effects of aging and DAT.

[unreadable] DESCRIPTION (provided by applicant): Daily encounters with verbal information are both visual (i.e., reading text) and auditory (i.e., spoken language comprehension). Research has established that as we age, we become less efficient readers. Compared with reading comprehension, however, much less is known about how listening comprehension is affected by aging. To fill this gap in the literature, we propose to conduct the first large-scale study of the determinants of age-related differences in listening comprehension across the adult life span by testing a sample of 490 adults between the ages of 20 and 90 years. Specifically, this study will examine four potential mediators (hearing acuity, processing speed, working memory, and speech perception) of the relationship between age and listening comprehension, all of which are strongly associated with deficits in older adults. The major goal of our study will be to determine whether these mediators affect age-related deficits in listening comprehension directly or indirectly and to evaluate the relative contributions of these variables using structural equation modeling. As part of our modeling efforts, we will evaluate both the linear and non-linear effects of age. By determining the best-fitting causal model of the data, we will be able to shed light on the theoretical mechanisms underlying age-related differences in listening comprehension and, at the same time, identify where rehabilitative efforts can be most effectively directed. This project represents a unique opportunity to explore the nature of listening comprehension and the dynamics of aging on performance by bringing expertise to focus on this issue from the areas of cognitive processing, the psychology of aging, general speech perception, and aural rehabilitation. [unreadable] [unreadable]