Sibling Risk-Taking in the Big Leagues

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When B. J. Upton hit a home run last Thursday night to help the Tampa Bay Rays defeat the New York Yankees, it was not the first time that day that Upton had gone deep. Just a few hours earlier, chatting in front of his locker, he had helped confirm the results of a recent study of sibling risk-taking behavior.

In the current issue of Personality and Social Psychology Review, Frank J. Sulloway and Richard L. Zweigenhaft went digging for evidence of siblings behaving differently in the vast database of baseball statistics. Given how younger siblings have been shown to take more risks than their older counterparts — perhaps originally to fight for food, now for parental attention — Drs. Sulloway and Zweigenhaft examined whether the phenomenon might persist to the point that baseball-playing brothers would try to steal bases at significantly different rates.

In fact they did: For more than 90 percent of sibling pairs who had played in the major leagues throughout baseball’s long recorded history, including Joe and Dom DiMaggio and Cal and Billy Ripken, the younger brother (regardless of overall talent) tried to steal more often than his older brother.

B. J. and his younger brother, Justin, a slugger for the Arizona Diamondbacks, are actually among the 1 in 10 exceptions (B. J., who at 25 is 3 years older than Justin, has been more of a speedy leadoff hitter, a position in the batting order often associated with base stealing). Yet B. J. nodded thoughtfully when told that scientists have found younger brothers tend to take more risks.

“He was always the one who would push things to the limit,” B. J. said of Justin. “When Mama told him, ‘Don’t ride your bike there,’ he would ride it. When Mama said, ‘Don’t stand on the bleachers,’ he’d stand up on the bleachers and fall and bust his head open.”

The finding by Drs. Sulloway and Zweigenhaft won’t revolutionize behavioral science, but it is an intriguing example of how the personalities of siblings may differ according to birth order. A visiting scholar at the Institute of Personality and Social Research at the University of California, Berkeley, Dr. Sulloway has published extensively on the effect of familial birth order on siblings’ relative rebelliousness, intelligence and even political activism.

Speaking by telephone from a research trip to the Galápagos Islands, Dr. Sulloway said that he did not expect the study to have any practical application for baseball managers, who base their rosters and lineups on players’ skills, not bloodlines. Nonetheless, he said, the study contributes to the understanding of sibling psychology because it offers evidence of how differences developed in childhood could continue well past puberty.

“We tend not to exhibit birth-order differences all the time in adulthood — we employ them in situations with siblings, because that’s where the behavior comes from,” Dr. Sulloway said. “But we found that here, and that’s significant.”

Scientists including Stephen Jay Gould and Edward M. Purcell, who won the 1952 Nobel Prize in Physics for work on magnetism in atomic nuclei, have dabbled in baseball statistics mostly as a diversion from more substantive matters. Dr. Sulloway said that baseball’s volumes of records since the 19th century present a unique opportunity for research. “We had 700 players and 300,000 athletic acts to look at,” he said. “As a behavioral scientist, that’s a data set you dream of.”

Baseball aficionados will surely second-guess the study. The authors examined how many times each player attempted to steal per time on base, measured by singles, doubles, triples, walks and times hit by pitch. Of course few runners steal home or even third base; it is also hard to steal second if a runner is already there, records of which are scant at best. Even if both brothers encountered that equally, baseball abhors such inexactitude.

The data was further converted logarithmically, and several other factors were considered, like age differences, body size and even the order in which the players were promoted to the majors — leaving the numbers relatively unrecognizable to morning box score scanners. And there remains the plausible issue of whether younger brothers learned baseball strategy more fully simply by watching their older brothers growing up, which Dr. Zweigenhaft, a professor of psychology at Guilford College in Greensboro, N.C., said could very well be a contributing factor.

Nonetheless, he said, “I loved working on this study, going over statistical patterns of so many famous names. It was like being at a ballgame, really.”