Perceptual Constancies: Size Constancy

At different distances, it seems like objects have different sizes; however, size constancy allows humans to perceive objects as having a constant size no matter what the distance. Size constancy also shows the relationship between distance and size. For instance, when humans see an object and know its size, it gives humans an indication of how far the object is.

For example, in the picture below, due to size constancy, we know that the shoe is very close to the camera, and the humans are very far away from the camera because humans are definitely bigger than shoes.