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And before football became our obsession it was the kinder, gentler sport of baseball that was known as the National Pastime of the U.S. But baseball does have its share of dangers, just check out those batting helmets.

NPR's Joe Palca has this story about a social scientist who performed a sophisticated analysis to find out when a pitcher is most likely to hit a batter in a baseball game.

JOE PALCA, BYLINE: Major League pitchers can throw the ball with great accuracy. And most of the time they try to throw the ball over the plate. But occasionally, this happens:


JOHN ROONEY: Bergman has a safe lead with Howard holding at first. And Holliday is hit on the right elbow by an inside pitch - two on with nobody out for Molina...

PALCA: That was John Rooney of KMOX Radio calling a playoff game last week, between the St. Louis Cardinals and the Philadelphia Phillies.

There a consequences for hitting a batter. He gets to go to first base. Sometimes it happens by accident, but sometimes it's on purpose to make some kind of statement. And Richard Larrick wanted to explore some of the reasons for that. Larrick is a psychologist at Duke University.

RICHARD LARRICK: Twenty years ago, I'd done a paper with some graduate students just showing that at hotter temperatures, pitchers are more likely to hit batters with pitches.

PALCA: Now, obviously heat couldn't be the whole answer but he was curious why pitchers were more likely to hit batters when it's hot. Was it because they would sweat more, and the ball might get slippery and hard to control. Or was it something more deliberate?

LARRICK: Laboratory research has shown that if you put people in a hotter room, they're more likely to act aggressively toward someone else.

PALCA: Sometimes without being aware of it. Now ballgames aren't played in a lab so to see the effect, Larrick looked through 50 years of baseball statistics.

LARRICK: We can look at every game and every plate appearance, and just look to see what the chances are of a batter being hit.

PALCA: As he reported in the journal Psychological Science, there was a definite pattern. Pitchers were more likely to hit a batter if earlier in the game one of their teammates had been hit. But that's not all.

LARRICK: It seems to be that main thing that changes with temperature is the desire to retaliate for my teammate being hit.

PALCA: In other words, pitchers were more likely to retaliate in the hot summer months. Larrick says that fits well with his laboratory research about people in hot rooms.

LARRICK: The same thing that someone else does to me, that could be ambiguous, whether it was designed to hurt me or not, is more likely to be interpreted as having hostile intent, which then provokes me to want to retaliate for it.

PALCA: Larrick doesn't know for sure if his theory about retaliation is correct. All he has to go on is the numbers.

LARRICK: I don't actually have any idea if this resonates with the players themselves.

BILLY RIPKEN: I think there could be something to that.

PALCA: Billy Ripken was a Major League player who's now an analyst for MLB Network. As a batter, he says you rarely know if a pitcher hit you on purpose.

RIPKEN: If you may be given a choice of saying, OK, was that an accident or was it not an accident? And you're a little bit irritable you might say, yeah. You know what? I don't care, I didn't like it.

PALCA: And there's no question that for baseball players, the dog days of summer can be annoying.

RIPKEN: When you're playing in Baltimore, New York, Atlanta in the middle of the summer, it's 95 degrees and 98 percent humidity - it's pretty miserable.

PALCA: But Ripken's colleague at MLB Network, Dan Plesac, has another explanation for Larrick's data. Plesac was a Major League pitcher for 17 years. He says it's a mistake to think that pitchers retaliate right away. Sometimes things happen early in the season against a particular team when for whatever reason you'd like to retaliate but can't.

DAN PLESAC: So you kind of put that in your file of, OK, the next time we play them there or they come to our place, you know, we're not going to forget what happened in April and May.

PALCA: And frequently that second meeting is in the middle of the hot summer.

Is Plesac right? Well, you don't hear this too often in sports stories, but the answer is probably more research is needed.

Joe Palca, NPR News, Washington.


MONTAGNE: And this is MORNING EDITION from NPR News. I'm Renee Montagne.


And I'm Steve Inskeep.

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