There are certain instances when an invasion of personal space is warranted in the name of some higher good: crowding into a basement for a concert; riding a spinning teacup ride at a carnival. And then there are contexts in which such a spatial violation triggers your primitive, territorial instincts—say, on an airplane, locked in a passive aggressive, increasingly sweaty elbow battle for the single armrest separating you from your row mate. It’s a real pickle: do what you want to do—confrontation!—and you’ve created a tense scenario that you will have to endure for the duration of your flight. But ceding the armrest sentences you to extended aerial discomfort, arms tucked into hips like some sort of frequent-flying, short-armed T-Rex.

If all travelers were compassionate, fundamentally good people, this would be an easy problem to solve. Either we'd all observe universal armrest etiquette—which says that the unfortunate soul riding sitting middle in this uncomfortable three-way would get both inside armrests—or we'd do as kindergarteners do and figure out a way to share. But as anyone who has ever watched a season of Bachelor in Paradise knows, the world is full of shit humans. And yes, yes, we know: when they take the low road, etc. But sometimes the high road sucks when you’re trying to enjoy Moana on your eight-inch screen, and you can’t because Nudgy Nate in 14E can’t keep Planet Elbow in his own damn personal solar system. And since you can't confront your neighbor any more than you can ignore him, you're left with one option: cunning. We called up body language expert Mark Bowden for some mile-high trickery.

If your seat partner is violating your personal space, return the favor…subtly.

“Drop something on the ground near them, and ask them to pick it up,” says Bowden. He suggests a pen. As social mammals, we’re designed to help each other, so saying, ‘No, I’m not going to pick that up,’ is, in effect, sociopathic behavior. Either they’ll pick it up, removing their arm from the armrest, and you’ll be able to swoop in—or they won’t, and then you’ll know you’re seated next to a sociopath, which seems like a good tidbit to file away.

This works with the air conditioning, too.

Bowden, a frequent traveler himself, says he’ll often pull a similar tactic by encouraging his seat mate to get some air. “You’re being helpful by going, ‘Oh look, your air conditioning is turned off. You’ll probably want that at some point.’ Their arm will go up. Great, that’s mine now.”

Know your enemies’ weaknesses (hint: it’s their joints).

Forearms are hearty, the meatheads of our skeletal structure, happy to bang around with other forearms, roughhousing, bones being bones. So as long as your jostling radius and ulna, you’re going to be swapping dead skin cells from tarmac to tarmac. But joints? Joints are tender, like poets. “You could go around, kind of reaching for your seat belt, and move your fingers to where their elbow is, and touch into that joint, going ‘Oh, I’m sorry, excuse me, I’m just trying to sort out my seat belt here.’ I guarantee they’ll move their arm.” Is it crazy? Yeah, a little bit. But not as crazy as going an entire flight without somewhere to rest your weary elbow.

Get really weird. But be prepared for some even weirder consequences.

“If you really wanted to, you could put your hand on theirs," says Bowden. "That would be a real pattern-interrupt. The top of the hand is very sensitive. There's no fat between your skin and your bones and the veins. If we're fighting over some arm space and I put my hand on top of yours, you're going to withdraw really quickly. It's going to be very, very odd. Or they're going to take it as a signal of intimacy. Any of the things that could win this battle obviously have risk of further escalation.” Escalation, of course, meaning anything from fisticuffs to making sweet, sweet lavatory love.

An easy way to avoid this: Be in Boarding Group 1.

If you get to the seat first, you can establish territory. And establishing territory is as simple as browsing Instagram, using the hand of the arm occupying the armrest. "We understand the mobile device as being a personal object of high worth," says Bowden. "That's why I can't just walk over and take your mobile phone. It's absolutely yours. If I have that in my hand, it's more likely that it'll trigger them [to realize], This is my precious, high-value area."

No matter what you do, hold the line.

"You can't even acknowledge them socially," says Bowden. "You have to keep on looking forward. If you turn your eyes and get eye contact, in that proximity, you're most likely to smile. To show them it's okay. And [if] they smile back, you might be triggered to try and share. Remember: it's not a space big enough for sharing. The moment you've shared, someone is going to push to win and there has to be a loser."

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