A shade of difference

Are the figures exactly the same colour?

Compare the shades of the grey figures. Then slide the display surface and see what happens to them.

The figures are the same colour. The shade of colour appears, however, to change when the surface of the display is moved.

This is called the colour contrast phenomenon, in which the shade of colour we observe changes in response to the colour surrounding it. When surrounded by a darker colour, the grey lightens and when surrounded by a lighter colour, it darkens. When surrounded by yellow, the figure turns bluish, and violet makes it yellowish. In this exhibit, however, the contrast effect appears to act in the opposite manner. The grey stripes have more contact surface with the colours next to them, but still black seems to cause a darker effect, white lighter, violet bluish and yellow yellowish.

This anomaly can be explained by the Gestalt laws of perception. They refer to perceptual methods which enable us to perceive entities based on individual observations, and to group or select perceptual stimuli from among others. Both the figure and the vertical stripes of the background are entities which guide our interpretation. We interpret the grey figure as a solid surface that is intersected by vertical stripes. On the other hand, we see the grey stripes as a part of the vertical striping. Hence, we are not comparing the grey colour to the colour next to it but rather, to the colour of the vertical stripe that forms a continuation for it. The Gestalt laws of perception concern e.g. the relationship between figure and background, proximity, similarity, continuity, familiarity and common fate.

Designers in different fields utilise these laws of perception in order to create, for example, products that are easy to use and comprehend, or to organise smooth traffic systems.