I’ve always been impressed with people who can smile with their eyes on command. When a photographer says, “Cheese,” their zygomatic major muscles lift the corners of their mouth, their orbicularis oculi muscles raise their cheeks and form crow’s feet around their eyes and they look so unbelievably happy.

I don’t usually force a smile when someone tells me to say, “Cheese” — I feel ridiculous feigning bliss on command. I smile in photographs but rarely with my teeth and never with my eyes. I guess that means I’m going to die sooner than people who really mean it.

A study published in Psychological Science late last month found that professional baseball players from the ’50s were more likely to reach the age of 80 if they sported Duchenne smiles in their official photographs — that is, smiles that involved both the mouth and the eye muscles. Researchers at Wayne State University also found that players with non-Duchenne smiles, those restricted to the mouth muscles, outlived those who didn’t smile at all.

With yearbooks coming out soon, it could be possible to predict the longevity of any graduating senior at USC. But for now, check out your student I.D. photograph or your Facebook profile picture.

How intense is your smile?

Scientists think Duchenne smiles indicate genuine happiness because it’s hard to contract the orbicularis oculi muscles around the eyes at will.

Past studies have found that Duchenne smiles can predict other positive life outcomes, such as marital success. Last year, a DePauw University study found that people who sported genuine, toothy grins in their yearbook pictures were more likely to have successful marriages than people with non-Duchenne smiles or those who didn’t smile at all. The latter were more likely to divorce.

However, the interpretation of studies like these has been somewhat misleading.

Matteo Marjoram | Daily Trojan

Ernest Abel and Michael Kruger, authors of the Psychological Science study, speculated that perhaps people with intense smiles in their photographs lived longer than people with weak or non-existent smiles because they are generally happier during their lives. They are “more likely to experience the health benefits of happiness, which has been linked with lower levels of stress hormones and a protein implicated in heart disease,” according to a New Scientist article about the study.

Although a smile that involves the eyes is probably a more accurate indicator of genuine happiness than a smile that involves only the mouth, most people who are aware they are getting their photographs taken are smiling on command. If anything, the intensity of your smile in a photograph reveals how good you are at faking happiness — not how happy you actually are.

After all, actors and actresses sport Duchenne smiles in their photographs all the time.

Other scientists have speculated that the reason Duchenne smiles in photographs predict longevity and other positive life outcomes is because they may reflect the person’s sociability. People who are better at conjuring expressions of happiness are better able to establish strong social networks.

I can buy this interpretation because research has established that the more friends you have, the more likely you are to live a long, healthy, happy life.

Matt Hertenstein, a psychologist at DePauw University who led the study about smile intensity and marital success, said he thinks the correlation between Duchenne smiles and positive life outcomes might be caused by conscientiousness. Perhaps people who give big, toothy grins in their photographs are simply more willing to obey a photographer when he tells them to say, “Cheese.”

This, too, makes sense. People who follow the rules are less likely to engage in unhealthy activities like smoking, drinking and other substance abuse. Conscientious Duchenne smilers are probably more willing to try to work through problems in an unhappy marriage or put on a happy face and pretend everything is okay, rather than get a divorce.

Also, conscientious people are more likely to have better social networks than non-conscientious people. They are more willing and able to convey the emotions they know they’re supposed to convey and conform to the expectations of a group.

So no matter what type of smile style you have in pictures, there’s reason to be proud of yourself.

If you’re a Duchenne smiler, you can rejoice because you’ve got a 70 percent chance of reaching the age of 80, as opposed to the 50 percent chance that non-smilers have. And if you’re not so great at smiling in pictures, at least you can be satisfied in knowing that you are a nonconformist.

After all, Einstein and Tolstoy and many other brilliant minds throughout history look miserable in most of their photographs and portraits.

Jean Guerrero is a senior majoring in print journalism. Her column “Scientastical” runs Mondays.