Feeling good - experiencing positive emotions - has been linked to enhanced performance at a variety of tasks. However, the typical research relies on laboratory experiments where a positive emotion is induced and performance at some problem-solving task is then assessed (e.g., Fredrickson, 2001).

Does this provocative result generalize outside the laboratory to outcomes that really matter, like job performance?

My colleagues Jeff Garofano, Brian McGuire, Nansook Park, and I recently presented a relevant study at the First World Congress of Positive Psychology, held in Philadelphia, PA. The study was an experiment of nature that asked how Major League Baseball (MLB) players perform at the plate on their birthdays. We assumed that most people feel good on their birthday, as friends and family members celebrate the occasion with cards, phone calls, and gifts. We assumed that MLB players were no exception, so the hypothesis tested was that their hitting would be better on their birthdays than during the rest of the season.

We looked at performance during the 2008 regular season, limiting our attention to the 182 players (among 983) with at least 400 official at bats. We wanted to focus on players who played regularly and were not pitchers, whose batting performance is poor at best. However, the results we found reflected the larger population of MLB players during the 2008 season and were unaffected by the age of the player or whether he batted from the right side of the plate, the left side, or both.

Among the everyday players, 69 had at least one plate appearance that fell on their birthday during the 2008 season, whereas the remaining 113 did not. Consistent with our hypothesis, players hit better on their birthdays than on other days during the season, and better on their birthdays than did other players during the season.

Batting average is the percentage of hits per plate appearance, and the birthday batting average among MLB players was a notable .306 (versus .275 for other days and .279 for other players).

Slugging percentage is the total number of bases per plate appearance, where a single = 1, a double = 2, a triple = 3, and a homerun = 4. The birthday slugging percentage among MLB players was again notable: .509 (versus .454 for other days and .440 for other players).

These results make sense in terms of the hypothesis that positive emotions enhance performance.

All of these MLB players are elite athletes who do well at a very difficult task. Nonetheless, on their birthdays they do even better. If every day were a batter's birthday, he would be a likely candidate for the Baseball Hall of Fame and would earn many millions of dollars more in salary.

The practical implication for major league managers is never to rest a batter on his birthday. Along these lines, the practical implication for everyone else - parents, educators, and workplace supervisors - is to capitalize on naturally-occurring positive emotions as well as to cultivate such emotions. Good results may follow.


Fredrickson, B. L. (2001). The role of positive emotions in positive psychology: The broaden-and-build theory of positive emotions. American Psychologist, 56, 218-226.

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