A first book in psychology / by Mary Whiton Calkins.

  • Mary Whiton Calkins
Date:
1910
Catalogue details

Licence: Public Domain Mark

Credit: A first book in psychology / by Mary Whiton Calkins. Source: Wellcome Collection.

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    In total color-blindness (if due to retinal and not to brain conditions) it may be supposed either that the retina contains only rods, and not cones, or that the cone-substance is as undeveloped as that on the rods.15 2. The Physical and Physiological Conditions of Visual Brightness and Extensity By a little amplification this account of physical and physio¬ logical processes may be expanded so as to explain also the consciousness of brightness and of visual extensity. The visual qualities are conditioned by the length, and the cor¬ responding number per second, of the ether waves; the visual intensities, that is, the brightnesses, are conditioned by the wave amplitudes; the visual extensities, or bignesses, are conditioned presumably by the diffusion of the waves in space. The physiological conditions of these elemental visual ex¬ periences are probably the following: The ‘qualities’ (ex¬ periences of color and of colorless lights) are conditioned by the mode of the retinal excitation (partial or total decompo¬ sition of a retinal substance), whereas visual intensities are conditioned by the degree of excitation; and visual extensities are conditioned by the number of nerve-elements excited.30 It must be noted, in conclusion, that color sensations stand in more constant relation to physiological than to physical conditions. The phenomena of color contrast offer an ad¬ mirable illustration.16 If one look fixedly for ten to twenty seconds at an illuminated green window and then look off at a neutral background, the background will appear not white or gray, but pinkish-purple; or, if the illuminated window is blue, the background will appear as yellow. That is,
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