When we look out across a field. how do we know one distant object is bigger than another, or that one is behind another? Why don’t we see everything “flat”, instead of in three dimensions, in proper relation to each other?
The fact is that we “see” things not only with our eyes but with our minds as well. We see things in the light of experience, And unless our mind can use the cues it has learned to interpret what we see, we can become very confused.
For instance, experience has given us an idea about the size of things. A man in a boat some distance from shore looks much smaller than a man on shore. But you do not say one is a very large man and the other a very small mao.
What are some of the other “cues” your mind uses? One of them is perspective. You know that when you look down the railway tracks they seem to come together. So you consider the width of the tracks and get an idea about distance. Experience tells you that near objects look sharply defined and distant objects seem hazy.
From experience, you have also learned how to“read” shadows. They give you cues to the shape and relationship of objects. Near objects often cover up parts of things that are farther away.
Moving the head will help you decide whether a tree or pole is farther away. Close one eye and move your head. The object farther away will seem to move with you, while nearer objects go the other way.
The combined action of both eyes working together also you important cues. As objects move nearer to you and you try to keep them in focus, your eyes converge and there is a strain on the eye muscles. This strain becomes a cue to distance.
Do We See In 2 Or 3 Dimensions?
We are 3D creatures, living in a 3D world but our eyes can show us only two dimensions.