Size Constancy

Size constancy explains how we infer the sizes of objects based on the distance they are away from us. We perceive things on the horizon or in the background to be bigger because things that are farther away look smaller. Experience along with inherent knowledge has taught us this.

In this picture, everyone looks about the same size. In reality the size of the man in the background is much smaller than the people in the front of the people.


http://psych.hanover.edu/krantz/SizeConstancy/page2.html

We see him as the same size because we know that things are meant to get smaller as they get farther away.