Now consider Victor at home. He smells cookies with his nose.

Victor in the hallway, sniffing. Cookies sit on the kitchen counter.

What his nose smelled went to his brain. His brain decided to go and look, so his legs walked to the kitchen.

Now consider a deer in the woods. It hears a twig snap with its ears.

A deer in the woods with its head up and its ears forward.

What its ears heard went to its brain. Its brain decided to run, so its legs ran.

Three chains: Dean and the bell, Victor and the cookies, the deer and the twig. In every one, the brain sits in the middle.

When an animal does not sense something, nothing about it goes to its brain, so it does not respond to it.