Properties of Transsaccadic Memory

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9309564 IRWIN Our eyes move from object to object in the world several times each second. We scan the world by means of saccades--fast eye movements that are separated by brief fixations during which the eyes are relatively still. Each eye movement causes visual stimulation to be swept across the retinas, producing a blur or smear that is not ordinarily perceived because vision is suppressed during saccades. Because of this suppression, we acquire visual information from the world only during fixations, when the eyes are still. For this reason, our visual information about the world is registered in isolated glimpses that are separated in time. Furthermore, the contents of these isolated glimpses are not identical, because different regions of the world fall on different parts of the retina when the eyes change position. Despite this rapidly changing and discontinuous visual input, we ordinarily perceive the world as unified, stable, and continuous. How the perceptual system accomplishes this has puzzled psychologists and vision researchers for over a century. One frequent hypothesis is that the contents of individual eye fixations are combined in memory across eye movements to produce a coherent mental representation of the visual environment. This research will investigate the characteristics of this hypothetical process. In particular, the research will determine how much information is remembered from one eye fixation to the next, whether some kinds of information are remembered better than others, and how this information is stored and combined across eye movements. The experimental procedure will involve having individual observers view visual displays on a computer terminal screen while their eye movements are monitored by an eyetracking device. During selected eye movements, the visual display will disappear and the observer's memory for that display will be assessed. For example, the observer may indicate whether a second display is identi cal to or different from the first display, attempt to report some particular information that was present in the first display, or name an indicated object in a new display as rapidly as possible. These responses will reveal what aspects of the original display are stored in memory, maintained across an eye movement, and used to relate successive eye fixations to each other. The question of how people perceive a continuous visual world across eye movements is a classic problem in perception. The research will advance the solution to this problem. In addition, the research will lead to the development of more sophisticated theories of spatial representation and spatial cognition in general. From a practical standpoint, the research will help human factors engineers design visual displays, and tasks that require multiple eye fixations on a display, to take best advantage of an operator's ability or inability to combine different kinds of visual information across eye movements. ***