3/16/2023 0 Comments Wku quicklinksNotice that in such situations (where observers can see the horizon and the viewed objects are standing upon the ground), then no information about distance to the object is necessary to visually perceive object size. If the observer in this case has an eye height of 1.6 m, then the statue’s size/height is 4 m. Sedgwick demonstrated that the size (i.e., height) of the statue, in this case, would be 2.5 times the height of the point of observation above the ground (i.e., eye height). The ratio of total visual size divided by the portion below the horizon is therefore 2.5. Imagine an observer looking at a statue (whose base stands upon the ground) that subtends a total visual angle (i.e., has an optical size) of 25°, but 10 of those degrees fall below the visible horizon. One important source of information, the horizon ratio relation, was described in 1973 by Sedgwick 1 (also see Warren 2). In many full-cue situations (e.g., outdoors in a natural daytime environment), there are multiple ways to determine size. Which source can be used depends upon the particular situation. When visually perceiving object size, there are a variety of optical sources of information. We effectively perceive a wide variety of object properties: their size, shape, surface texture or material, as well as their location and movement. The use of vision and haptics (i.e., active touch) permits people and a wide variety of other animals to perceive environmental objects and thus enables successful everyday behavior. The ability to visually perceive object size is well maintained with increasing age, unlike a number of other important visual abilities. Finally, there was no difference in either the accuracy or the precision of the observers’ judgments between the two age groups, despite the fact that the older adults were more than 50 years older than the younger adults (mean age of the younger and older adults was 22.3 and 74.1 years, respectively). In contrast, in complete darkness (where linear perspective information was unavailable), the accuracy of the observers’ judgments was poor. The judgments were just as accurate in the dark with linear perspective condition as in the full cue condition, indicating that linear perspective serves as an important source of optical information to support the perception of object size). Each observer made repeated judgments for the same square stimuli (the task was to adjust a separation until it matched the perceived size of the squares), enabling an evaluation of precision as well as accuracy. An experiment evaluated the ability of 30 younger and older adults to visually judge object size under three conditions: (1) full cue, (2) in the dark, with linear perspective, and (3) in complete darkness.
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