According to last Wednesday's New York Times, NFL players might be able to choose jersey numbers beyond the numbering system devised in the 1970s. This requires, for example, that linebackers can have numbers in the 50s, and quarterbacks may select any number between 1-20.
This year, Reggie Bush, running back (destined for a number from 20-49), wants the numeral 5 as he starts his #1 draft pick career with the New Orleans Saints. This isn't new, as a few players in the past few years have questioned the system. John Branch's article talks about the details, and if you like football & numbers, you'll enjoy the article.
My questions are more of a cognitive nature. If a running back gets a quarterback's number (Kerry Collins, former NY Giants QB, wearing jersey #5, for instance), will the fans think he's a running back or a quarterback? The Stroop Effect suggests that if words are presented in colors that aren't the same (ie, the word "blue" in red letters), it will take a long time for you to realize that the color is red rather than blue. So, I predict that fans will be more likely to ... well, they'll be confused by someone wearing a number that's not "right."
This got me to thinking about how players choose numbers, which led me to think of synethesia, where people see letters as colors (a = red) or feelings as color (pain = orange) for example. Do (some) football players & other athletes "see" themselves as a certain color in the same way a synesthetes see colors when they hear vowels? Maybe Reggie Bush "sees" himself as number 5 and nothing else will do.
You can take the girl out of the Cog Sci department, but you can't take cognitive science out of the girl.