Vision and Perception
Visual Pathology, Visual ProcessingConclusion
Perceiving is a constructive act. Using the data supplied by the senses and his knowledge of the world, the perceiver constructs his reality of the moment. Since the sensory systems have a limited capability for acquiring information, the constructed reality will reflect not only the present data but the person’s interpretation of the information and its context. The perceiver does not simply record the actions of the physical world but reconstructs that world moment by moment. There are two factors constraining the construction of the percept: data and resource limitations. Data refers to the amount of information that may be acquired by a perceiver. This places the first restriction on the final construction of what is perceived. The influence of past experiences and knowledge on the creation of the percept is what is referred to as resource limitations. This entry will focus on the restrictions on the quality of the percept as influenced by data limitations associated with aging.
The descriptions are based on the average performance of adults as they age. As a presentation of normative information, it is not a prescription for what happens to each person. There is as much heterogeneity in the performance of elderly adults as there is in younger persons. This point is made because it is inappropriate to create a stereotype of an aging person as one who is affected by all of the changes described below. Instead, it is better to view this information as a guide to the potential changes that may occur to varying extents in the population.
In examining changes in vision and perception, it is important to consider the scope of the visual system. The eye is a complex structure whose optical properties, governed by the lens, and the shapes of the cornea and eyeball, as well as the neural structure and function of the retina dictate the quantity and quality of the sensory data that is acquired. These centers extract different types of information from the signal pattern, such as color and shape. Alterations in structure or function in one or more areas may underlie the age associated effects discussed in this entry.
It has been shown that there are multiple factors that limit visual data acquisition by older perceivers. It also has been demonstrated that in some tasks the sensory limitations may be compensated by using stronger visual stimuli. An appreciation of the nature of the variables that influence our construction of reality will help us to understand the differences in perceptual experience as we age.
GROVER C. GILMORE
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