The world around us is mobile and changeable: a car drove past at high speed, a man passed, the wind shakes the crowns of the trees, and the sun peeped out of the clouds, illuminating everything around, then it disappeared again. Imagine if we saw everything exactly as it is reflected in the retina of our eyes. A car that moved 50 meters away would look like a toy, a white sheet of paper would turn gray as soon as the sun went down behind the clouds, the crowns of trees would be perceived as on a jumping picture of a broken TV. Fortunately, this does not happen.

So, despite the continuous variability of the objects around us, we perceive them as relatively constant in shape, size, color, etc. This feature of our perceiving system is called perceptual constancy. Why do we need it? First of all, if we didn’t have it, then we would have to reconsider our behavior in relation to surrounding objects every moment. Perceptual constancy helps us to distract ourselves from insignificant, temporary changes and perceive objects as something relatively unchanging.

Perceptual constancy definition

Perceptual constancy is one of the fundamental properties of perception, since we live in a constantly changing world, starting from the peculiarities of lighting and ending with our own movements, as a result of which the angle of view, the features of gravity, etc. change. In general, perceptual constancy is the relative stability of the perceived features of objects when the conditions of perception change. For the first time, the constancy of perception was researched in 1889 by Martius, who worked for W. Wundt. 

Perceptual constancy examples

Constancy has been studied mostly in the visual modality, however, there is evidence of the relative constancy in other modalities. For example, when one perceives the mass of a load lifted in different ways (with one or two hands), assesses the sound volume, or observes the distance that changes, etc. In the visual modality, various types of constancy have been studied, which include the constancy of:

  • lightness 
  • color
  • size
  • speed of movement
  • object shape
  • spatial position. 

Perceptual constancy psychology

Color constancy is the relative constancy of the color of an object, despite the change in the spectral composition of the light falling on it. Due to this, the red surface is perceived to be the same color regardless of what kind of light it is illuminated with – electric, luminescent or solar.

Constancy is associated with the objective aspect of perception. This means that we reflect not so much the sensory properties of the object, but the object as a whole, as it exists. It is proven that constancy is based on taking into account the situation of perception. 

An experiment illustrating this fact was conducted by David Katz. It showed that if you organize the conditions of perception in such a way that the observer does not have information about what kind of object he perceives, then the constancy will disappear. If you take two identical white sheets of paper and place one in the sun and the other in the shade, then for the observer they will both be the same color – white. This shows the constancy of lightness. However, if you observe these two sheets through an artificial pupil, for example, take the third sheet, cut out a small hole in it, and look at both sheets through this hole, then a sheet in the shade will appear much darker than a sheet lying in an illuminated place. In this case, the presence of an object is a necessary condition for perceptual constancy.

Another example of perceptual constancy

  • A piece of coal on a sunny summer day will be about eight to nine times lighter than chalk at dusk. However, we perceive it as black, not white. At the same time, the color of chalk will be white for us even at dusk.
  • A truck moving in the distance will still be perceived by us as a large object, despite the fact that its image on the retina will be much smaller than its image when we stand next to it.
  • The height of the same person from a distance of 3.5 and 10 meters is perceived by us as unchanged, although the size of the image of this person on the retina will be different depending on the distance.
Svitlana Drach

Svitlana Drach team member

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