User:Gabor seres

Emmert experiment
A perceptual experiment by Emil Emmert psychologist (1844–1911). The experiment is based on the size constancy.

Besides the localization and recognition, there is another function of our sense system: to keep the size of the objects in spite of that the image perceived to our retina is changing constantly. Thanks for the evolution we experience the objects as they are in the real life and not as our eyes perceives them. Usually we sense the objects as they are relatively constant independently on the changes of light criterias, on the place where we see them from or on the distance between us. Our cars do not seems bigger even if we are approaching them, their form will not be distorted furthermor, their colour does not change even if we give artificial light. This phenomenom is called prceptual constancy.

The most studied constancy is the size constancy, or phenomenon as we perceive constant size of the objects independently on their distance. As an object goes farther, usually their size does not decreases as wee are looking them. Keep e coin in front of us from 30 cm away and move it till arm distance. Does the coin seems smaller? Obviously not, but size of the retinal image of the coin is twice bigger than the coin with 30 cm far away.

In the Emmert experience keep a book in front of us with normal reading distance in good light conditions. Fix our look into the middle of the figure for 1 minute and look to a farther wall. We can see the post-images of the two circles that seem bigger than the stimulus. Now let’s see a paper close to our eyes. The post-image is smaller than the stimulus. If the post-image disappears it can be restores by blinking.