Donald Trump has said he doesn’t like shaking people’s hands, and he seems to take his discomfort out on the people he has to greet. More than once, the US president has been seen yanking and twisting people’s arms when he’s supposed to be shaking them. He was at it again today, when he held, patted, and jerked around Shinzo Abe’s hand for a full 19 seconds. We spoke to a body language expert to understand what exactly was at play in that handshake. Trump and Abe sat down for a handshake photo-op at the White House, before they flew down to Florida to play golf at Trump’s Mar-a-Lago resort. Japan’s prime minister initiated the handshake, asking “Shall we shake hands?” Then Trump extended his hand, patted the back of Abe’s hand three times, and pulled the Japanese leader closer to ask (in reference to the Japanese-speaking photographers in the room) “What are they saying?” “Please, look at me,” Abe answered. Trump seems to have completely misunderstood Abe’s translation as an instruction, as Jezebel’s Gabrielle Bluestone noted, and began staring at the prime minister with a wide smile, even after Abe pointed at the cameras with his other hand to show Trump where he should be looking instead. Trump yanked Abe’s hand and patted the back of his hand again before letting go. “When you cover somebody’s hand, you’re portraying yourself as being closer than you really are. It’s for perception management,” says Joe Navarro, a body language expert based in Florida, and author of the book What Everybody is Saying. “The only time you should be tapping somebody’s hands is if you’re their grandmother, but certainly not between two grown adults.” That would typically make people feel uncomfortable and invaded. “Because the back of your hand is your intimate zone,” says Navarro, comparing the experience of the hand-pat to the feeling you get when somebody stands too close to you. “You are entitled to touch the palm of their hand when you shake hands, but not the intimate zone.” But Trump didn’t just pat the back of Abe’s hand, he yanked and pulled the prime minister toward himself in a signature move he’s been doing since his stint hosting The Apprentice. More recently, he’s used the move on Mitt Romney, Neil Gorsuch, Nancy Polosi, Rex Tillerson, and Mike Pence. Often, it turns a regular old handshake into a comical tug-of-war, with Trump twisting people’s arms into strange angles. It’s like playing “jiujitsu with your hand,” says Navarro. ”All that it does is that it leaves a bad taste in your mouth and causes psychological discomfort.” “Frankly, it’s rude,” he adds. In Japan, people typically greet each other with a bow, or a handshake and then a bow—in either case, you maintain some distance between the person you are greeting and avoid physically intimate gestures. It’s easy to imagine how uncomfortable Abe must have felt after the unsolicited yank. Although the handshake likely lasted longer than it naturally would because it was a photo-op, Navarro says it would have been more appropriate if Trump just held Abe’s hand steadily without pulling it around. Abe glanced up at the ceiling after Trump finally let go, looking somewhat exasperated, with his mouth slightly open. He looks relieved that the long handshake is finally over. He then repositions himself using the armrests of his chair, while Trump gives a double thumbs-up for the cameras. “Strong hands,” Trump says.