Winner and Loser Effects in Major League Baseball Double Headers

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Across the animal kingdom it has been observed that outcomes of conflicts are influenced by past experiences, whereby previous winners are likely to keep winning and losers are likely to lose again. These so-called “winner and loser effects” are hypothesized to result from factors such as information acquisition and endocrine responses following the initial bouts. This paper applies the understanding of this phenomenon to a novel domain: patterns of winning and losing in Major League Baseball (MLB) double headers. By accessing archival data available from www.espn.com, we report on the incidence of a single team winning both games (sweeps) versus each team winning one game (splits) in MLB double headers over the last 13 years. Consistent with previous research on winner and loser effects, we show that sweeps are significantly more common than splits and that there is a home field advantage in this context. Results indicate that disparity in opponent quality or skill, as measured by the difference in team records outside the double header match, was not a significant predictor of whether the outcome resulted in a split or a sweep. In contrast to our hypotheses, there was no difference in the margin of victory in games between sweeps and splits. Overall these results add to the existing literature on winner and loser effects, provide a framework for pursuing further research in MLB, and suggest that winner and loser effects may be present across a variety of other forms of human social interaction.