The dancers hold each other so close. Indecently close. Enviously close. So close that you feel like a Peeping Tom watching them slowly circle the room.

They don’t care. They’ve forgotten that you’re watching. Given what researchers have discovered, this might be the only thing they’ll forget.

Dancing, it turns out, helps the brain fend off the decline in mental sharpness that can accompany aging.

In fact, among other physical activities such as tennis, golf, swimming or bicycling tracked in a 21-year study, frequent dancing was the only one to offer protection against dementia.

Argentine tango was singled out because it follows no set pattern, with partners in a duet of prompts and reactions created on the fly.

The press of one’s calf against another’s cues a responding move. A shoulder drops. Balance shifts. A leader’s turned-out knee becomes a fulcrum around which a follower unwinds. The physics of velocity, momentum and gravity translate into art.

It’s not easy, and partners struggled at times. But there’s a word for when the dance becomes seamlessly intuitive: tangasm.

Each week, several hundred Minnesotans dance the tango — in classes, at parties, among diners at a Dinkytown restaurant. Instead of memorizing a prescribed series of steps, their brains respond to the tango’s trademark spontaneity by building new neural pathways. Having more pathways bolsters our ability to remember stuff, make decisions and age well mentally.

This isn’t breaking news. A study by the Albert Einstein College of Medicine in New York City was published in the New England Journal of Medicine in 2003. Various studies since then have confirmed the findings.

So why aren’t we all dancing cheek to cheek?

Tango instructor Lois Donnay offers one theory, born of an earlier career as a marketing manager for health care products. “I know how hard it is to get the word out about therapies that are not monetarily successful for someone,” she said, which is a deft way of saying: Big Pharma likes its ka-ching.

“They’d rather find a pill than tell someone to go out dancing.”

Here’s another theory for the reticence: Some Minnesotans would rather face down a rabid raccoon than hold another person as close as tango demands — especially if he or she is a stranger. Which they very well could be.

In Donnay’s classes, students dance with different partners throughout the evening, which helps them learn to feel different aspects of leading and following. But changing partners also epitomizes the Argentine tango custom of encouraging sociability.

One other thing: The tango you see on TV where the guy’s hair is shellacked and the woman is half-naked? That’s ballroom tango, a flashy and meticulously choreographed set of steps, and an entirely different animal from the languorous and serendipitous Argentine tango.

“Tango isn’t just a dance, it’s a philosophy,” said Donnay, who in 1999 was the first president of the Tango Society of Minnesota. “As yoga is to exercise, tango is to dance.”

Seduced by the music

Ken Speed of Columbia Heights first was drawn in by tango’s distinctive music.

“The music seduces you,” he said of the genre scored for guitar, violin, flute, piano, double bass and bandoneón — the Argentinian version of a concertina. The songs have the bones of classical music, yet are haunting and ultimately Latin in their sinuous beat.

“Ballroom tango is like singing in a choir, while Argentine tango is like singing a jazzy duet with someone else,” Speed said. “Its complexity is what keeps you coming back.”

Julia Robinson of Minneapolis began taking tango lessons after she was widowed.

“It was a way to have a social life without having to date or having to sleep with someone,” she said with a wry smile. An avid world traveler, she’s found that Argentine tango is understood internationally.

“I’ve danced tango in Germany, Japan, the Netherlands,” she said. “The form is always the same. In Barcelona, no one spoke English, but I could dance with all the people.”

Gary Rauk of Edina is an avid swing dancer, and still enjoys it, but these days finds himself drawn to tango.

“Swing dancing is so joyful, but tango,” he said with a sigh, “tango is beautiful.”

Rauk also brought up the research linking tango dancing to improved brain health: “It stretches your neural system in creative ways, really causes you to expand how you think.”

Despite the research about the tango and brain health, Donnay said she couldn’t recall anyone enrolling in class specifically to improve their cognitive ability. Mostly, that’s considered a fun bonus.

“You have to be present in a way you don’t with other dances,” she said, adding that tango seems to appeal to intellectuals — scientists, lawyers, architects, physicians. “I think it’s the physics and mechanics that are involved.”

At a recent class, students worked on techniques with Spanish names such as sacada and enganche. Students don’t learn steps as much as responses. Women don’t passively “follow” as much as interpret their partners’ signals, which requires that split-second brain-building decision-making.

As Donnay explained, “A woman holds her body in such a way that a gentleman can create art with her body.”

One heart, four legs

Learning tango begins by “walking in the embrace,” moving across the dance floor while holding someone close. “It’s a way of learning how to get another person to feel what you want them to do,” Donnay said.

Being comfortable inside each other’s personal space is a common hurdle for students. Speed recalled a new partner who was struggling with dancing in a stance that tango dancers call “one heart, four legs.”

“I stood in front of her and said, ‘Pretend I’m a tree and you fell right into me.’ She really had to chew on that for a couple of minutes, but then she got it and it was a piece of cake after that.”

While the Tango Society of Minnesota has about 300 members, most of them in the Twin Cities area, spreading tango across a Germanic-Scandinavian state is challenging.

Donnay shook her head over a session in St. Cloud.

“We’re working on Duluth, but it’s slow. And when we tried Hibbing — ” she trailed off, rolling her eyes, then brightened. “But the chapter in Rochester is doing well.”

After 90 minutes of rather serene dancing, the students nonetheless were sweating from its isometric nature. Time to unwind.

As the women slipped out of their heeled dance shoes into comfier footwear and the men wiped their brows, Donnay opened a bottle of wine.

Twisting the corkscrew, she said with a laugh: “This is what probably keeps us from getting too smart.”