See what sort of explanation you can think of for this: Statisticians began noticing that a large number of professional hockey players in the National Hockey League had birthdays in January and February (Grondin, Deshaies, & Nault, 1984).
Maybe being born in winter makes someone love winter sports more? Getting ice skates for your birthday? But November and December should also be good for that, and those months were marked by relatively few birthdays of NHL players. Also, the same pattern began to emerge in other sports as well, especially soccer, where the effect has been found all over the world (for review, see Musch & Grondin, 2001). It is statistically undeniable. What might cause it? Astrology? No.
Th e unequal birthday pattern emerges from a curious mix of nature and culture. In hockey, as in many sports, pro athletes generally got their start while they were children. Children’s leagues are grouped by age, but rather than automatically moving from league to league on their birthday (which might disrupt teams), kids are grouped for each season based on a cutoff date—typically January 1st. Th us, when the season starts in November, if you’re already 9 or will turn 9 by the end of December, you play with the 9-year-olds, but if your birthday isn’t until after January 1st, you play with the 8-year-olds. Why does that matter? Nine-year-olds are usually bigger and stronger than 8-year-olds. Kids born late in the year grow up always being matched against others who are older, stronger, and faster, so they tend to drop out of the sport. Meanwhile, the lucky kids with birthdays in January will grow up always being among the oldest (and therefore biggest and strongest) children in their league, which puts them at a physical advantage. Th is advantage helps them be successful and makes the sport fun for them.
You might think the effect would wear off as children grow up. But many of the younger children have already dropped out. Moreover, coaching increases the problem. Coaches want to win, so they bestow their attention and more playing time on their best players—which often means their oldest (hence biggest, strongest, and most coordinated) ones. Children born after January 1st end up getting more training and more opportunities to compete, while those born late in the year spend more time on the bench.
Th e so-called relative age effect (Musch & Grondin, 2001) is not limited to sports. It has been shown in school performance also (Dickinson & Larsen, 1963; Hauck & Finch, 1993). Children who end up getting classified as gifted often benefited from starting school later than others, which made them older than their classmates (Maddux, Stacy, & Scott, 1981). Before you start planning to have your babies in January, however, note that school cutoff dates are different from sports ones. In many schools, it is the children born in the summer (just before school starts in September) who are destined to be always the youngest in their class and therefore suffer disadvantages in school (DeMeis & Stearns, 1992).
Sport in general is a combination of nature (innate physical abilities) and culture (practice, training, and arbitrary rules). Star pro athletes are thus neither made nor born: They need both the gifts of nature and the benefits of culture. And, it appears, the luck to be born on the right side of the cutoff date also helps!
Th is chapter began with the story of little Brenda. Th e failure to raise the boy as a girl suggests that being male has some elements of nature that are not easily overcome by culture. Yet manhood also has strong aspects of culture. Research on “precarious manhood” by Vandello, Bosson, Cohen, Burnaford, and Weaver (2008) showed some cultural differences in beliefs about being a man versus a woman. Many cultures require boys to prove themselves before they can claim to be men, whereas all girls grow up to be women. Even among modern American college students, manhood is regarded as more tentative and requiring of proof than womanhood. In one of their studies, students read about people who said they felt they were no longer a man, or no longer a woman. Loss of womanhood seemed difficult to fathom, and students thought it must mean that the woman had undergone a sex change operation. Loss of manhood was more readily seen as a result of social factors, such as not being able to provide for one’s family.
Th us, in a sense, society regards womanhood as a biological achievement, whereas manhood requires a cultural achievement. (Note that both are cultural opinions, however!) Th e need for men to prove themselves is relevant to many gender differences. In Vandelloetal.’s studies, threats to a man’s masculinity caused him to feel aggressive and anxious, whereas parallel threats to a woman’s femininity produced no such response.
