What do you see? 

Yellow vase, with symmetrical curves on either side resembling the profile of a boy.

Show me!

Do you see a vase or two faces? Either way, you’re correct!

vase labeled with words "FACE" near edges, and "VASE" in the middle.

You might be able to see the vase and the faces. But you probably can’t see both at the same time. Why is that?

Your brain has to make a decision about which part of the picture is the object and which part is the background. Maybe you see the faces. That means your brain is interpreting the rest of the picture not as a vase but as the background. Maybe you see the vase instead. In that case, your brain is interpreting the rest of the picture not as faces but as the background.

Imagine if you could see more than one version of your surroundings at once. It would be confusing! That’s why your brain evolved to select one interpretation at a time.

Check out another illusion like this one!

Drawing which could be interpreted as a duck head or a rabbit's head.

What animal do you see? 

Show me!

The illusion shows a duck and a rabbit!

The duck is looking to the left; the rabbit to the right. Your brain is selecting only one interpretation of the image at a time, so you can only see one animal at a time.

a duck head, and a rabbit head side by side.

Next, find out how your brain copes with incomplete information.