And from the rough and tumble world of British media, we move to hockey. Last night, the Washington Capitals knocked the defending champion Boston Bruins out of the National Hockey League playoffs in a dramatic game seven overtime victory. This opening playoff round has been filled with upsets and also penalties. Nine players have been suspended so far for violent play. Now some research shows that hidden psychological factors play a role in how hockey penalties are doled out. NPR science correspondent, Shankar Vedantam, joins us often to talk about curious sorts of social science research. Welcome.

SHANKAR VEDANTAM, BYLINE: Hi Renee, how are you?

MONTAGNE: Pretty good. So, what is this new research about?

VEDANTAM: So, as a word of background, Renee - when a hockey player commits an aggressive foul, the referee can penalize a hockey player by putting him in the penalty box, and typically, this is for two minutes. And during that time, the player's team plays with only four men on the ice, while the other team plays with five men on the ice. This is called a power play and it's a significant scoring opportunity for the team that has more players. Now there's this new research by the psychologist at the University of Florida, his name is Gregory Webster. He's found that the color of the uniforms that the players are wearing plays a significant role in how often the teams get penalized. And in particular, he's found that one color gets teams penalized the most.

GREGORY WEBSTER: Teams that wore black jerseys were penalized more - significantly more - than teams wearing other colored jerseys.

VEDANTAM: And Webster has found that teams wearing black get an average of about two minutes more, per game, in the penalty box.

MONTAGNE: What would cause certain colors to get more penalties?

VEDANTAM: The short answer is, I don't think anyone knows. This was a very large study that has an empirical finding. It wasn't necessarily designed to answer the question why. That said, Webster has a few theories. The most obvious theory is that hockey is a game that's being played on the ice, and so teams that wear colored uniforms, the referees are more able to spot fouls because players wearing colored uniforms stand out more clearly on the ice. Now, one problem with that theory is that teams wearing black uniforms got penalized significantly more than teams wearing other dark colors. There's another explanation, which is that wearing dark jerseys simply makes players, somehow, more aggressive. That they're actually committing more fouls when they wear the darker colored jerseys, and that's why they're ending up in the penalty box more often. And finally, I think there's a third explanation. And that is that the teams wearing darker jerseys are the victims of, you know, unconscious biases on the part of referees. Hears Webster again.

WEBSTER: There's a very strong cultural association that comes through in how we think about colors, in terms of white being associated with good and black being associated with bad. Many of us are raised, from childhood, with some of these associations. And over time, we develop a, kind of, cognitive bias. And that's been shown time and time again in social psychology.

MONTAGNE: Time and time again, not, obviously, only in hockey then?

VEDANTAM: So, this has actually been demonstrated in several sports. Several years ago, there were researchers at Cornell University who conducted an experiment. They had high school and college football students, essentially run the same football plays. In some cases, the teams wore white uniforms, and in other cases, they wore black uniforms. And when the researchers showed the videos of these plays to referees, it turned out that the referees penalized the team significantly more when they were wearing the black uniforms, even though the plays were completely identical.

MONTAGNE: That's Shankar Vedantam, who joins us regularly to talk about research on topical issues. Tell him your theories about hockey jerseys on Twitter @hiddenbrain. And while you're at it, you can follow this program @morningedition.

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