Richard Schweickert - US grants

One of the most important limits in human information processing is the capacity of short term memory. The size of the memory span is correlated with IQ and is related to cognitive deficits found in psychotic and brain damaged individuals. In spite of its importance, no constant, noncircular measure of capacity in terms of items or chunks has emerged. Recently, several investigators have found that the memory span for a type of material is equal to the number of items that can be pronounced in approximately 1.5 seconds. Since this time seems to be the same for all types of material, a reasonable interpretation is that it is the mean duration of the memory trace. If so, the duration is no doubt a random variable, and we would be interested not only in its mean, but in its variance and density function. A means for estimating these is proposed. A variable that affects memory span can do so in two ways, either by affecting the pronunciation rate or by affecting the trace duration. Three variables known or suspected to influence memory span, namely noise, acoustic similarity and output modality will be investigated to see where their effects occur.

The Mesozoic continental margin of the southwestern United States was the site of major compression involving overthrusting and accretion of terranes to the active margin. However, the extent of Orogen-parallel strike-slip faulting is poorly constrained. Recent stratigraphic and structural data suggests the presence of a major (>500 km displacement) cryptic intrabatholithic fault of Early Cretaceous age in the Sierra Nevada. If confirmed, this discovery will have far reaching consequences, including the necessity to radically revise Jurassic and earlier paleogeography and tectonics of the western Cordillera. This project will critically test several specific predictions of this new model in an effort to establish the model's validity and to explore its impact on tectonic interpretations of the Mesozoic of western North America.

Cognitive processes take time. It takes a human at least half a second to subtract "1" from a number and key in the answer, and subtracting "2" takes markedly longer. The relationships among reaction times taken by different tasks can tell us details about the way the underlying processes are organized. This research will develop further a particular method for discovering process organization through reaction times based on the mathematical theory of scheduling, a theory concerned with how best to organize the processes involved in carrying out a task using a PERT (Program Evaluation and Review Technique) network. As the theory of scheduling is ordinarily used, one knows the way in which the processes are arranged in a PERT network and how long each one takes, and one wants to determine how much time will be required to carry out the entire task under various conditions. The cognitive psychologist faces the inverse problem, knowing how long it takes to carry out the task under various conditions, and wanting to infer the structure of the network and to estimate the time required for each process. At this point, we know how this works in dual tasks, tasks in which two stimuli are presented, each requiring a separate response. It seems to be the case that more than one perceptual process may be executed at the same time, as may more than one movement-related process, but processes such as deciding and remembering must go on one at a time. Because the latter processes demand attention, they appear to use a central processor which carries out only one of them at a time. Some of the experiments will investigate dual tasks, with an emphasis on learning about the order in which these central processes are carried out. Scheduling theory indicates that some orders are more optimal than others, and the experiments will investigate whether subjects spontaneously use the optimal order, or can learn to do so with practice. Using the optimal order would, of course, reduce reaction times. Saving a few tenths of a second or improving accuracy by a few percent would not make much difference in everyday tasks, but might make a substantial future improvement in tasks such as air traffic control, in which it may be possible to optimize the type of information people receive and the order in which they receive it. Other experiments will investigate the organization of mental processes when reading statements in the PASCAL computer language; such statements need to be carefully read when debugging programs. The most ambitious experiments will investigate the processing involved in recall from short-term memory. When a list of items, a phone number for example, is recalled immediately, a few items in the middle are not so much recalled as reconstructed from the degraded fragments of the items that remain in memory. By timing subjects as the recall aloud, it is possible to study the processes involved in such reconstruction.

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