For the young-at-heart adults out there, we have good news about keeping your inner child alive and kicking (and making the outside match!).

Here is the only excuse you ever need to act like a big kid again, because the verdict is in, acting young keeps you young! ...no need to tell us twice.

The research: In 1981, Harvard psychology professor Ellen Langer set up a short but classic experiment: For five days, a group of men in their seventies left their homes and temporarily lived in a house set up to look like 1959, with dated magazines, dated music, and Ed Sullivan on a black and white TV. When the men walked (or shuffled) through the door, they were told to put on Mad Men-era clothing and act as if they were 22 years younger.

The surprise: After they left, they took a battery of tests and seemed to actually be a little physically younger. Acting like their middle-aged selves had left them with better flexibility, dexterity, and even slightly better eyesight. It was a small study, and never published. But it pointed Langer in the direction of decades of further research that supported the simple idea that if you act younger, your body will be a little younger too.

The research inspired a simple new video. As part of an ad campaign, Kiehl's, the skincare brand, asked a group of people to say how old they felt—and then dance as if they were that age, as a reminder that age on a calendar isn't much of a reflection of health.

The campaign "is about embracing our 'second age'—the age we feel," says Chris Salgardo, president of Kiehl's USA. "When we were building this, we said things like 'we hope that it will inspire the 15-year-old budding entrepreneur to start a company, the 40-year-old to get out and dance at that club, inspire a 60-year-old to practice for that triathlon.' But the bigger, loftier hope is that it inspires everyone who watches it to simply feel good in their own skin."

They saw dance as the best way to express age. "The Internet is pretty good support of this—if you look up 'old lady dancing' you find endless numbers of hysterical old women dancing to hip hop," says Evan Slater, partner and creative director for Night Agency, which produced the ad. "It's one of those forms of expression that no matter how old you get, you can also express yourself if you're in the mood. It's a universal thing, regardless of age or culture or language. Dance is sort of an easy equalizer."

Though casting included a couple of professional dancers, most of the people in the film are ordinary people reacting to being asked to express their age through dance.

"A lot of times you try to find yourself using the edit room to tell a story that isn't there," says Slater. "In this case, I was amazed at how the theory wasn't just a theory—we didn't have to concoct a story. It's true. You find people and ask them how old they feel, and give them a very simple vehicle to express it, and they can. It's a genuine thing."

Source: Adele Peters, for Co.Exist