Subjective constancy

Subjective constancy or perceptual constancy is the perception of an object or quality as constant under changing conditions.

Vision

The high brightness of the actual lamp is perceived also when displayed on a computer monitor, where its individual pixels in fact cannot be displayed brighter than the 100% white level of the computer monitor. The same principle would apply to an image printed on paper.

There are several types of perceptual constancies in Visual perception:-

• Shape constancy
• Size constancy

Shape constancy is a type of perceptual constancy. When a man is observing an object that he is familiar with, although he observes it at an angle which makes the shape of the object on the retina change, he will still view the object as its original shape which means the perception of shape is relatively stable.

For example, wherever a man looks at one book will view that as a rectangle but not a parallelogram.

• Color constancy

This means perceiving a color as "constant under changing conditions of illumination" and "is the achievement of a very complicated 'calculation' by an unconsciously working apparatus within our central nervous system".

The facts behind color-constancy phenomena...are that we require fine color discriminations less frequently than gross discriminations, and when gross discriminations enable us to maintain focus on objects of prime interest, we 'systematically overlook' differences beyond the necessary degree of fineness. The mechanism which accomplishes this 'systematic overlooking' is the information-processing system of the organism, and the principle according to which it is accomplished is that this system never expands more of its capacity on a given perceptual task than is necessary according to the current needs and interests of the agent.

— Sayre

• Lightness constancy
• Distance constancy
• Location constancy

Music

In music, subjective constancy is the identification of a musical instrument as constant under changing timbre or "conditions of changing pitch and loudness, in different environments and with different players."

Speech

In speech perception this means that vowels or consonants are perceived as constant categories even if acoustically, they vary greatly due to phonetic environment (coarticulation), speech tempo, speaker's age and sex, speaker's dialect, etc.

References

• Erickson, Robert (1975), Sound Structure in Music, University of California Press, ISBN 0-520-02376-5 .
• Lorenz, Konrad (1961), "The Role of Gestalt Perception in Animal and Human Behaviour", in Lancelot Law Whyte, Aspects of Form, Indiana University Press, pp. 157–178 
• Sayre, K.M. (1968), "Toward a Quantitative Model of Pattern Formation", in Frederick J. Crosson and Kenneth M. Sayre, Philosophy and Cybernetics, Simon and Schuster, pp. 149–152 .