Do players become more aggressive when they wear black?

Here's one of the most surprising legitimate findings I've seen in sports analysis. According to a 1988 study by Mark G. Frank and Thomas Gilovich, wearing black uniforms makes players more aggressive. Moreover, referees and fans subjectively rate those players as more aggressive, even when they're not.

The study seems pretty thorough. (And it's an pretty decent read.)

First, Frank and Gilovich (F&G) gave volunteers pictures of all NHL and NFL uniforms, and had them rate the jerseys for "malevolence." It turned out that jerseys with black in them were rated the most aggressive.

In the NHL, the top six were: Vancouver (black at the time in 1988), Philadelphia (orange with black trim), Boston (black), New Jersey (non-black; black trim would appear a few years later), Pittsburgh (black), and Chicago (black trim).

In the NFL, the top five were the Raiders (black), Pittsburgh (black), Cincinnati (black trim), New Orleans (black), and Chicago (dark blue, but the authors classify as black because the volunteers thought they were black).

I don't think there are any other teams with black in their uniforms, but I might have missed some. If I'm right, then black uniforms took all the top slots, with the exception of one spot taken up by the New Jersey Devils.

(By the way, the least aggressive ratings went to the Miami Dolphins (aqua and orange) in the NFL, and the Hartford Whalers (blue and green) in the NHL. My beloved Toronto Maple Leafs didn’t scare anyone either, finishing third last.)

Having now established that black uniforms signify malevolence, the authors now checked whether the black-clad teams actually were more aggressive. It turned out that they were. In terms of penalties, the black teams out-offended the non-black teams, with 98% signficance. In the NHL, the same was true at a 99.5% significance level.

A quick glance shows that the effect couldn't be caused by just one team. See for yourself; in visual terms, here are how the black teams ranked:

NHL: XXX--X---X-------------
NFL: X-X---XX---X----------------

Moreover, there were a couple of natural controls in the NHL in the late 1970s, and those were the ones where the results really shocked me. In the middle of 1979-80 season, the Pittsburgh Penguins abruptly changed from blue uniforms to black. Astonishingly, their penalty minutes immediately rose by 50%, from 8 minutes per game in blue uniforms to 12 minutes in black. Furthermore, after having been average or below in PIMs for eight of the past nine seasons, the Penguins went on a streak of four above-average seasons.

The case of the Vancouver Canucks is similar. After the 1977-78 season, the Canucks went from blue uniforms to (ugly!) black ones. The next season, their PIMs shot up from almost exactly average, to 2 SD above average (and this is before their trade for Tiger Williams). Like the Penguins, they maintained an above-average rate for three more seasons after that.

What could be causing this? One explanation is that the black uniforms made the players more aggressive. Another is that the black uniforms made the team *appear* more aggressive, and so the referees penalized them more. A third explanation is that teams with black uniforms have management that wants to play more aggressively (although this explanation is more reasonable for the Penguins and Canucks, whose management actually chose the team colors rather than inheriting them).

The authors ran little experiments to test the first two possibilities.

First, they recruited some experimental subjects, and randomly assigned them black or white T-shirts. Then, they let the subjects choose one out of several competitions to play. The black-shirted subjects chose more aggressive games.

Second, the authors staged several aggressive football plays, one where the white-shirted team was the aggressor, and (an identical) one where the black-clad team was the aggressor. They then showed tapes of those plays to referees and casual fans, asking them to decide whether the play was a penalty. Both groups called significantly more penalties when the aggressor team wore black. Further, when they showed the plays in washed out black and white, so it was no longer obvious that the dark shirts were black in color, the subjects called penalties at an identical rate for both teams.

So it does seem that wearing black (a) makes competitors more aggressive, and (b) makes them *appear* more aggressive. At highly significant levels. I am blown away.

Hat Tip: Daniel Engber of Slate