constancy
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constancy
[kon´stan-se]the quality of remaining stable or unaltered.
form constancy the ability to recognize forms and objects as the same in spite of variation in environment, position, and size.
object constancy the capacity to understand that an absent person or object exists and will return.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
con·stan·cy
(kon'stan-sē),The quality of being unchanging
[L. constantia, fr. consto, to stand still]
Farlex Partner Medical Dictionary © Farlex 2012
con·stan·cy
(kon'stăn-sē)The quality of being constant.
[L. constantia, fr. consto, to stand still]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
constancy
Perceptual phenomenon whereby the properties of certain objects appear to remain relatively constant, despite changes in the stimulus characteristics which induced the perception. All constancies occur only within a limited range.
brightness constancy Perceptual phenomenon whereby the brightness of an object appears to remain relatively constant, despite changes in the level of its illumination. Example: white paper appears white whether it is seen in sunlight or in the weaker or yellower illumination of a light bulb. Syn. lightness constancy.
colour constancy Perceptual phenomenon whereby the colour of an object appears to remain relatively constant, despite changes in the spectral composition of the incident light.
shape constancy Perceptual phenomenon whereby the shape of an object appears to remain relatively constant, despite changes in the viewing angle. Example: A circle held obliquely to the line of sight appears more circular than it should due to shape constancy although its retinal projection is oval.
size constancy Perceptual phenomenon whereby the size of an object appears to remain relatively constant, despite changes in the viewing distance (and therefore of its retinal image size).
brightness constancy Perceptual phenomenon whereby the brightness of an object appears to remain relatively constant, despite changes in the level of its illumination. Example: white paper appears white whether it is seen in sunlight or in the weaker or yellower illumination of a light bulb. Syn. lightness constancy.
colour constancy Perceptual phenomenon whereby the colour of an object appears to remain relatively constant, despite changes in the spectral composition of the incident light.
shape constancy Perceptual phenomenon whereby the shape of an object appears to remain relatively constant, despite changes in the viewing angle. Example: A circle held obliquely to the line of sight appears more circular than it should due to shape constancy although its retinal projection is oval.
size constancy Perceptual phenomenon whereby the size of an object appears to remain relatively constant, despite changes in the viewing distance (and therefore of its retinal image size).
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann