Lying Eyes: A smile is a thin disguise.

O most pernicious woman!
O villain, villain, smiling, damned villain! ...
That one may smile and smile, and be a villain.
~ Hamlet

I can trace my enthusiasm for psychology back to reading Hamlet in high school. There's nothing like a great piece of literature to excite one's passions and Hamlet certainly is rife with gems of the mind.

This one from Act 1, Scene 5 goes straight to the core of dual nature of the human smile. We humans have complicated emotions and they are intimately tied to the intricate sets of muscles that lie just under the surface of our skin. Lie - yes - those muscles also help us lie. But to keen observers, they also give away the lie.

So just how do you catch one of those damned villain liars smiling through his or her teeth?

You can see how good you are at it by taking a fun, quick test by clicking the picture below, or clicking here.
I bet you found it was pretty easy as long as you paid attention to the right muscles. It's all in the muscles.

Genuine smiles are expressed with the eyes and the mouth. Emotions researchers call them the 'Duchenne smile' as opposed to the 'polite' or fake smile. The Duchenne smile is named after a French neurologist, Guillaume Duchenne, who back when America was fighting a Civil War, was busy mapping the muscles of the face. He discovered the muscles around the eyes - the ones that when they contract give you crow's feet - could not be moved voluntarily. He couldn't force himself to smile with his eyes, only with his mouth.

This was serious business for him too. He used a precursor of today's electrodes to force individual muscles to move, and in classic psychological form — he experimented on himself.

Although the archived images are grotesque, his experimentation mapped 100 unique facial muscles. His crowning achievement was the differentiation of fake from genuine smiles. False or even half-hearted smiles used only the muscles of the mouth. But, "the sweet emotions of the soul," he wrote, "activate the pars lateralis muscle around the eyes."

Tried as he could, he could not get those eye muscles to contract by willing them to, and that is the key. For those muscles to contract, the emotion of happiness must be felt. Researchers in the 2oth century later figured out that those muscles aren't even connected to the same portion of the brain that control other facial muscles. It's as though they have their own circuitry.

It's no surprise that politicians and celebrities are some of the best subjects to turn to for the observation of these so-called polite smiles. It's no accident that politician and polite share the same word origin.

Primatologists, this one especially, like to point out that we can see the evolutionary roots of the human smile, both kinds, in the facial expressions of chimpanzees.

Chimps have a polite smile and genuine smile too. The polite smile acts as an appeasement, given when there's a need to pacify a disgruntled rival before things escalate. This smile is given with a wide closed-mouth grin with both sets of teeth showing. These faces are easy to find in online photos of chimps trained to be actors. It's a face often directed at the trainer and sometimes deliberately elicited for TV and film because it makes people think they're smiling and happy. They aren't. These are false smiles just as much as are the false smiles of a disingenuous politician or crappy TV actor.

The other chimp smile — the genuine one — can best be spotted during play and in laughter. It is often but not always an open-gaped grin, with only the lower set of teeth showing. The chimp genuine smile always covers the upper teeth.

The photo at the right shows a chimp playing blind man's bluff. A certain group of chimps in captivity started playing the game. They plug their fingers over the eyes while 'blind.' It causes much hilarity for the young and old alike.

From an evolutionary standpoint, this makes good sense because an appeasing smile, meant to prevent a potential attack, shouldn't advertise that you're about to bite. Thus — the closed mouth. To further convey no harm is intended in a genuine state of happiness, chimps will go a step further — they'll close their upper lip over their large and potentially deadly canines.

Humans have long since lost whatever sizable canines we used to have eons ago, giving way to a far more subtle signal involving the eyes rather than the mouth.