use (one's) noggin

To use one's own intelligence and intellectual ability; to think logically and rationally. ("Noggin" here is slang for head or brain. Often said as an imperative.) Come on, Dean, I know you can figure this out on your own. Use your noggin for a change! I can't believe you were arrested for selling marijuana. What were you thinking? Why don't you use your noggin once in a while?