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Vision Res.(06) Braly

Ways of Seeing Visual Perception: Physiology, Psychology and Ecology Theories of Vision from Al-Kindi to Kepler (Chicago History of Science & Medicine)
Ways of Seeing Visual Perception: Physiology, Psychology and Ecology Theories of Vision from Al-Kindi to Kepler (Chicago History of Science & Medicine)

Research into Visual Perception conducted by Braly

From the mid-1920s to the early 1940s the influence of past experience on human visual perception was a popular research area. Many investigators employed arrangements of simple two-dimensional geometrical shapes, sometimes alone and sometimes embedded in more complex forms.

Braly considered that Gottschaldt’s results related more to the recognition of visual units (determined by lines, contours and spatial relations), than to the effect of past experience on perception.

Braly conducted experiments to determine the influence of the perception of certain visual forms upon the subsequent perception of other visual forms. Those experiments involved presenting simple geometrical forms incl. triangles, quadrilaterals and pentagons to observers. The figures were represented by arrangements of dots because the perception of groups of dots for any given figure was assumed to depend more upon subjective, attitudinal factors, influenced by past experience, than was the perception of outlined figures.

The first nine slides for each experiment comprised the impression-series, and the last nine (or eleven) slides comprised the test series. In each of the first five experiments 20 observers were given the impression- and test-series and 20 observers were given only the test-series. Each slide was displayed for approximately 0.175 seconds, after which observers were asked to draw the figure or figures whose corners were represented by the dots in their relative positions. Only if the dots could not readily be seen as indicating a particular figure, were the observers asked to draw the dots (rather than the figures) also in the positions in which they appeared.

Braly concluded that the experimental results indicated that the perception of visual stimuli may be significantly modified by past experience resulting from the previous perception of other visual stimuli, modification that might take the form of changes of the form of figures perceived, or as additions of new figures in the total visual perception.

Braly’s results were in complete disagreement with Gottschaldt’s and increased debate. Subsequent investigators largely discontinued the use of the simple geometric forms and their results generally opposed Gottschaldt’s conclusion that past experience was of little consequence, or at least had a lesser effect on perception than that due to the nature of the ‘whole’ objects viewed.

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This section includes summaries of historial research and theories of human visual perception of simple two-dimensional objects. For more about the human visual system see The Eye, Parts of Eye, Eye & Vision Disorders, Ophthalmological Procedures.

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