I kind of write about this in my book: smilers versus non-smilers. I'm convinced we all fall into one of these two categories.

Smilers are liked. Non-smilers are not liked.

We cozy up to smilers. We avoid non-smilers.

Which might explain why a lot of us don't much flip over Muqtada al-Sadr. Not only does this cleric not smile. He scowls, which is even worse than not smiling.

He's right up there on the nasty charts with Usama bin Laden, who doesn't smile either. Both men have their followers, but it's got to be fear. They aren't scoring points on the warm and fuzzy front.

I suspect John Kerry has problems smiling, though when he does, he does loosen up a lot. He should take a cue from Al Gore, who in his debates with George Bush, never smiled, but did sulk and hiss. I think it cost Al.

President Bush is a smiler. Although he should probably be careful, because his smiling sometimes becomes a smirk and the Washington press corps hates smirks -- which might be why he's smirking in the first place.

I think his predecessor Bill Clinton got out of a whole heap of trouble because he was a great smiler -- maybe a bit too smooth for some. But he dodged a lot of bullets with that smoothery.

John Kennedy? Smiler. Richard Nixon? Non-smiler.

Winston Churchill? Smiler. Adolph Hitler? Non-smiler.

You get the point. Smile and the world's your oyster. Scowl and you're an oyster… without a pearl in sight!

Watch Neil Cavuto's Common Sense weekdays at 4 p.m. ET on "Your World with Cavuto."

Neil Cavuto serves as senior vice president, anchor and managing editor for both FOX News Channel (FNC) and FOX Business Network (FBN). He is anchor of FNC's Your World with Cavuto - the number one rated cable news program for the 4 p.m. timeslot - as well as the FNC Saturday show Cavuto on Business. He also hosts Cavuto on FBN weeknights at 8 p.m. In addition to anchoring daily programs and breaking news specials on FNC and FBN, Cavuto oversees business news content for both networks and FNC's weekend business shows, including Bulls & Bears, Forbes on Fox, and Cashin' In. Click here for more on Neil Cavuto.