From Home Run Balls to Signed Hats, Why Do We Love Chasing Freebies?

You may have heard about the angry Philadelphia Phillies fan who, at a game in Miami on Sept. 5, confronted a father, accusing him of stealing a home-run ball from her and giving it to his son, inciting an internet furor.

That came days after another sports-related internet uproar: A business executive from Poland was caught on camera taking an autographed hat intended for a child at the U.S. Open. After a social media backlash, the man, Piotr Szczerek, apologized.

Then there is the report from Page Six of a woman biting a child in the Hamptons over a T-shirt that was shot out of a cannon at a free concert in August, part of a weekly summer series.

If it seems as if adults have forgotten how to behave at public events when presented with the prospect of a freebie, it’s hard to quantify. People have long dived into the stands to capture a wayward foul ball or headband thrown into the crowd by an N.B.A. player from the tunnel.

From a psychological perspective, one reason heated interactions happen at sporting events is a natural human “level of arousal,” according to Matthew Mulvaney, an associate professor of human development and family science at Syracuse University.

In a group environment, Dr. Mulvaney said, blood pressure is likely to be higher, especially if a game is competitive, and this can trigger more aggressive behavior.

There is also a theory in psychology, the frustration-aggression hypothesis, which posits that a key source of anger is having a goal blocked. (An example: being stuck in traffic when running late for a meeting.) So pursuing a home run ball in the stands — and being blocked by someone else, as appeared to be the case with the Phillies fan — can result in an expression of frustration.

Additionally, audiences have long been fascinated by giveaways at events. T-shirts. Bobblehead dolls. Armbands.

Sentimentality is a powerful emotion. So while a lone home run ball may not have much monetary value, a fan may see it as “a wonderful thing to have, either for reminiscence or for association with the team or event,” Dr. Mulvaney said.

Because professional sports has become such a lucrative business, there are more opportunities for souvenirs, and more opportunities for conflicts to break out as a result.

It wasn’t always this way. Dr. Patrick McBride was a bat boy for the Milwaukee Brewers from 1969 to 1976. Back then, he said, he was forbidden from giving foul balls and bats to fans by the team’s stingy ownership. Players were discouraged from doing so as well, he said.

“I always used to think to myself, ‘This is ridiculous,’” said Dr. McBride, a professor emeritus in the department of medicine at the University of Wisconsin-Madison.

Dr. McBride, 71, recalled that when he was with the Brewers, the stars would invite fans — almost always children — to line up and then they would sign every autograph. But as the years went on, adults began appearing more and more and the players realized their autographs were being sold.

Generally, leagues don’t have guidelines on how to handle free merchandise or balls. But teams and leagues do have general codes of conduct for fans. For the N.B.A., one stipulation is that players and fans “respect and appreciate each other.”

There also are no defined rules for how adults should handle game items.

“You have every right to reach your hand up as much as anybody else,” said Lizzie Post, a host of the “Awesome Etiquette” podcast and a great-great-granddaughter of Emily Post, the authority on social behavior. “I think if it’s more clearly headed toward the kid, or if in your excitement you reach over the kid to get it, that’s when I’m going to give it to the kid.”

But that doesn’t mean adults are obligated to do so, Ms. Post said.

“We aren’t beholden to just give everything to children just because they’re around or in the vicinity,” she said.

Michael Carter Jr. was a ball boy from age 15 to 30 for the New Jersey Nets, the New Jersey Devils and the Knicks. Mr. Carter, 49, recalled trying to get keepsakes, such as towels and autographs, to children attending games as much as possible.

“It makes the night even that much more special for a child,” said Mr. Carter, who now works in real estate. “It’s almost like Christmas.”

He recalled that adults, from his perspective, were more polite about pursuing game memorabilia when he was working in the 1990s and 2000s.

“It was different back then,” he said. “Adults weren’t muscling kids. If anything, it was the adults that were speaking up on behalf of the kids.”

It may be tempting to view this as generational crankiness. Indeed, plenty of foul balls, hats and similar items get tossed to children without incident. But it is also true that sports memorabilia has become an extraordinarily profitable industry, worth billions, incentivizing adults to pursue signed and game-used items more aggressively.

A famous dispute arose in 2001, when Patrick Hayashi and Alex Popov both got their hands on Barry Bonds’s single-season record 73rd home run ball. Popov sued Hayashi. A judge ruled that they were co-owners of the ball and that the ball must be sold, with the two splitting the proceeds — $450,000 — evenly.

Now, there are far more opportunities for free keepsakes at games as teams and their corporate sponsors are under more pressure to counter the convenience of watching games at home and boost attendance, said Lisa Delpy Neirotti, an associate professor of sport management at George Washington University.

“It is the scarcity or rarity that creates urgency, be it a fan or a collector,” she said.

Ms. Saber, the former Celtics cheerleader, recalled the exuberance with which fans at the TD Garden would receive the shirts she would toss, or the free keepsakes that parachuted from the rafters.