Click through the images.

Profile of a bald man wearing glasses.

Look at the drawing. What do you see?

line drawing which could be interpreted as a man's face or a mouse.

Let's try another: 

A mouse.

Show me!

Did you see a man in the first drawing and a mouse in the second?

The two drawings you saw are exactly the same. Did they look different to you? If so, it’s because of an effect known as priming. If you look at the photo of a mouse first, you’re more likely to see the drawing as a mouse. Looking at the photo of a man first, you’re more likely to see the drawing as a man. The first picture changes how you see the second.   

Why does this happen? Your senses flood your brain with information, and you can’t possibly pay attention to it all. To help you survive, your brain evolved to decide quickly what to focus on.

A mouse; A drawing which could be a man or mouse; Profile of a man's face.

Check out another illusion like this one!

Young boy in raincoat shielding himself from rain with an umbrella.

Listen carefully… What’s that sound?

(Make sure your sound is turned on.)

Show me!

It’s the sizzling sound of bacon!

Did you think it was the sound of rain? Sometimes it’s hard for your brain to identify something from sound alone. So your brain brings your senses together: what you hear is connected to what you see and feel.

So if what you see is a rainy scene, what you hear might sound like a downpour.

But with a different picture, you may recognize the sound for what it is: the sizzle of frying bacon!

Next, find out how your brain corrects for changes in lighting.