Body & Senses
Why do we have two eyes?
Puschel looks with one eye, then with both. What changes?
The short answer
Our eyes look at the world from two slightly different positions. The brain combines their images. The differences help us judge distances. One eye can also use clues about depth.
An imagined Wusel scene
Puschel and Flauschi investigate
Puschel looks at a tree behind his thumb. He closes one eye at a time: his thumb seems to jump sideways! Flauschi tries too. They notice that the thumb stayed still; only their viewpoint changed.
Try explaining it
Why does your thumb seem to jump when you switch which eye is open?
Choose a), b) or c), then explain your choice.
- a)Each eye has a different viewpoint.
- b)The eyes move the thumb when the view switches.
- c)Both eyes see from the same position but at different times.
Show the explanation
Correct: a): Each eye has a different viewpoint.
Our eyes look at the world from two slightly different positions. The brain combines their images. The differences help us judge distances. One eye can also use clues about depth.
Explore in more detail
Here you will find longer explanations and further details. You can explore them together.
Understand step by step
How it works – simply explained
Two viewing positions
Your eyes sit side by side. They view a nearby building block from slightly different directions, receiving slightly different light information.
Differences give clues
The brain can compare the two views. Their differences help many people judge depth and distance. The block does not have to move.
Other clues count too
An object hiding part of another is usually in front. Such clues also help without two equally good eyes. People orient themselves in different ways; the drawing shows only one part.
Why two views can help judge distance
A nearby block hides slightly different background parts for the left and right eye. The brain can compare these differences for distance clues. Size and overlap give further clues, so people with useful sight in only one eye can also judge distances.