"Touch predicts performance through fostering cooperation between teammates," says Dacher Keltner, a professor of social psychology at University of California Berkeley. "You can communicate really important emotions like gratitude, compassion, love, and anger just through brief touches."

Whether to celebrate, congratulate, or even commiserate, touching among athletes permeates sports from youth leagues to the pros, among men and women athletes. Long considered a way to build team spirit, these interactions may hold even greater benefits: One season-long study of NBA behavior suggests it just might help a team win.

It happens in every game. A hand extends upward to deliver a high-five or down low to slap a teammate’s behind. Or fists are bumped, continuing a legacy that dates to Stan Musial, who thought closed fists were more hygienic than handshakes. In hockey and football, helmets are knocked. Chest bumps and bear hugs are popular, too.

Keltner's students charted touches in the NBA during the 2008-09 season. The two teams that did the most touching — not related to game action — were the Celtics and the Lakers. The Celtics had the third-best record in the league, though they lost in the second round of the playoffs. The Lakers had the league's second-best record and won the championship.

The player that did the most touching that season? Boston's Kevin Garnett, by a wide margin.


Celtics forward David Lee, who won a championship last season with Golden State, says touching is an underrated aspect of team building in the NBA.

"Every team has talent, but the team that gets along the best and has each other's backs wins,'' Lee says, adding that he gets energy from high-fives.

"I think that stuff is contagious," he says. "You run into a timeout and the whole bench gets up and congratulates one another. That kind of stuff is what keeps the energy up during a game and a long season also."

Since the 2008-09 study, touching has probably increased, says Michael Kraus, a psychologist who conducted the NBA study and now teaches at Yale University. "In part, it's a changing culture where the brotherhood that extends to physical contact has expanded and you don't have to feel weird about it.''


New England Patriots receiver Julian Edelman and defensive coordinator Matt Patricia shared a hug. Stan Grossfeld/Globe Staff

Celtics forward Jared Sullinger believes that touching helps you win, because it's an indication of being unselfish and it helps develop trust.

"I think there's a correlation, definitely,'' he says. "That means you're outside yourself. You're all about team, and you are just constantly celebrating the little things."

The Celtics don't officially encourage touching, says Danny Ainge, president of basketball operations, nor do they discourage it.

"It's like, whatever their personality is," Ainge says. "KG was a toucher and I think that's great. But you can't really force someone to be something they're not. Larry [Bird] was not a toucher. They're both really, really, really good and they are both winners. I think good players win whether they touch or not."

But touching certainly seems to have increased in the NBA since Ainge's playing days. First of all, there's the ritual of a handshake, high-five, or fist-bump after a free throw — even a miss. No one knows who started this tedious tradition, but former Celtic Cedric Maxwell called whoever he was "an idiot."

Ainge isn't fond of foul line contact, either. "You can't just get a hug for making a free throw," he says. "It has to be earned."

The great Celtics teams of the 1980s were not touchy when they went to the charity stripe, Ainge recalls.

"Larry usually didn't want to be touched in between shots, and neither did I, and neither did Kevin [McHale]," he says. "I'm not sure anyone on our team did."


But current Celtics center Tyler Zeller defends the practice.

"It says just because you missed, you didn't kill the team,'' Zeller says. "We are still with you, still behind you."

Evolutionary process

Touching in sports has certainly become more flamboyant over the years. The Berkeley researchers recorded fist-bumps, high-fives, chest bumps, leaping shoulder bumps, chest punches, head slaps, head grabs, low-fives, high-tens, and hugs (full and half).

But the changes occurred gradually and sometimes by happenstance.

Musial, looking to avoid the germs spread by a handshake, may have invented the fist-bump, according to a St. Louis Post-Dispatch columnist. The first documented high-five, according to ESPN, was between Dodgers Glenn Burke and Dusty Baker in 1977, as Burke greeted Baker at home plate on the occasion of Baker's 30th home run, on the last day of the season.

"His hand was up in the air, and he was arching way back," Baker explained in an ESPN interview. "So I reached up and hit his hand. It seemed like the thing to do."

Red Sox reliever Koji Uehara grew up in Japan, where high-fives are not as prevalent. But once he learned the technique, he became unstoppable.

"I have been high-fiving since I came to the US," Uehara says through translator C.J. Matsumoto. "I'm not doing it to rally the team. It is because I just came out of the game after a stressful inning. I'm just letting everything out.''

It will never show up in box scores, but Red Sox slugger David Ortiz probably leads the league in hugs. After he smacked his 500th home run last season, he hugged at least 40 people — players, coaches, and staff.


"I hug my teammates," says Ortiz. "We started doing that, and now I see everybody in the league doing it, which is fine because we are family. As much time as we spend together, we are real family here. So why not?"

Hall of Famer Pedro Martinez hugged former teammate David Ortiz at a Fenway Park ceremony to honor Ortiz after he hit his 500th home run. Stan Grossfeld/Globe Staff

Tiffany Field, director of the Touch Research Institute at the University of Miami School of Medicine, says just as much — in a much more scientific tone.

"It not only rewards each other's good moves in a psychological sense but also relaxes them into a de-stressed/parasympathetic state in a physical sense," she wrote in an e-mail.

Digit Murphy, cofounder of the Play It Forward Sport Foundation, says women hug all the time. "That's the way we're wired," says the legendary hockey coach.

"But I think men touch more in sports. You want to know why? I don't think they get to touch normally in their regular lives as much. Sports is a way that they can express themselves without being sexual."

Variance between sports

In which sport do players do the most touching? Malcolm Butler of the Patriots and Mookie Betts of the Red Sox say it is basketball. They both played the sport in high school.

"You don't have pads and helmets on," says Butler. "They are out there in a condensed area. In football, we have a much bigger field."


Hockey players are more low-key than their counterparts in other sports, says the Bruins' Brett Connolly.

"With baseball players and NBA players, it's a lot more showtime," says Connolly. "They are more flashy than we are. I have no idea why. We were taught at a young age to be respectful, be classy, be very sportsmanlike."

The Bruins fist-bumped after a goal earlier this season. Stan Grossfeld/Globe Staff

Also in hockey, everyone wears bulky gloves, except when fighting. But the Bruins' Brad Marchand says gloves are irrelevant.

"It's all the same thing," Marchand says. "You're showing that chemistry between each other. It shows how close guys are. It builds relationships more and more and you feel close and you build that trust with each other."

Before Patriots games, defensive coordinator Matt Patricia goes player-to-player giving out bear hugs. And Rob Gronkowski says the players huddle up before and after each game in the locker room — hands on helmets, arms around shoulders. "It's just coming together as a team," he says. "We huddle up, get close to each other, and know that we're going to give all we've got for each other."

Stan Grossfeld can be reached at grossfeld@globe.com.