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A text-book of experimental psychology.On the visual perception of size and direction.

A text-book of experimental psychology.: On the visual perception of size and direction. The visual perception of size depends on two principal factors,—the size of the retinal image and the distance at which the object is estimated to be. Micropsia at the Fixation Point.—The size of the retinal image is considerably influenced by irradiation. Irradiation occurs in consequence of the diffusion of light on to neighbouring retinal areas. Such an overflow is, as we should expect, much more marked with a large than with a small pupil. Owing to irradiation, a white square on a black ground appears larger than an actually equal black square on a white ground. The apparent acuteness of the right angles within the annexed diagram (fig. 10) is due to the same cause. When the pupil is dilated under the influence of atropin, the size of letters printed in black type is considerably reduced. This form of micropsia under atropin is likewise due to irradiation. It has been called "micropsia at the fixation point." The Dependence of Apparent Size on the Relation of an Object to the Fixation Point.—The apparent size of an object also depends on its position relatively to that of the fixation point. We have already seen reasons for considering the fixation point as the central point or nucleus of our binocular field of vision, in terms of which all other, nearer or farther, objects in the field are interpreted. In uniocular vision it is easy to convince oneself that objects which are nearer than the fixation point appear to be larger, and that those which are farther than the fixation point appear to be smaller, than they would appear when directly fixated. (PsycInfo Database Record (c) 2023 APA, all rights reserved) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png

A text-book of experimental psychology.On the visual perception of size and direction.

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Publisher
Longmans, Green and Co
Copyright
Copyright © 1909 American Psychological Association
Pages
293 –307
DOI
10.1037/13628-022
Publisher site
See Chapter on Publisher Site

Abstract

The visual perception of size depends on two principal factors,—the size of the retinal image and the distance at which the object is estimated to be. Micropsia at the Fixation Point.—The size of the retinal image is considerably influenced by irradiation. Irradiation occurs in consequence of the diffusion of light on to neighbouring retinal areas. Such an overflow is, as we should expect, much more marked with a large than with a small pupil. Owing to irradiation, a white square on a black ground appears larger than an actually equal black square on a white ground. The apparent acuteness of the right angles within the annexed diagram (fig. 10) is due to the same cause. When the pupil is dilated under the influence of atropin, the size of letters printed in black type is considerably reduced. This form of micropsia under atropin is likewise due to irradiation. It has been called "micropsia at the fixation point." The Dependence of Apparent Size on the Relation of an Object to the Fixation Point.—The apparent size of an object also depends on its position relatively to that of the fixation point. We have already seen reasons for considering the fixation point as the central point or nucleus of our binocular field of vision, in terms of which all other, nearer or farther, objects in the field are interpreted. In uniocular vision it is easy to convince oneself that objects which are nearer than the fixation point appear to be larger, and that those which are farther than the fixation point appear to be smaller, than they would appear when directly fixated. (PsycInfo Database Record (c) 2023 APA, all rights reserved)

Published: Feb 13, 2012

Keywords: size perception; micropsia; fixation point; retinal areas; apparent size; retinal image; binocular field; irradiation

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