Four psychologists at the University of Amsterdam were in a bar, talking about recent publications. One article was on soccer strategy. The other was on how dogs wag their tails. The dog study reported that when pets see their masters, they wag their tails to the right. The other article was about penalty kicks. The group began wondering whether goalies, in making that split-second decision as to which way to jump, might favor one direction.
Penalty kicks ought to be a near-perfect exercise in randomness. The ball is placed twelve yards from the goal. The player tries to kick it in without the goalie’s intercepting it. As long as he does that, the kicker’s team scores.
For the goalie the physics are unforgiving. The ball will be traveling at about 125 miles an hour and enter the goal about a fifth of a second after the kick. That’s not enough time for the goalie to react. He has to guess where the ball will be and leap in the correct direction before the kick. (The rules used to say the goalie could not move until the kick. Had this been enforced, the goalie’s task would have been a physical impossibility.)
When the goalie guesses the direction of the kick, he stands about an even chance of preventing the score. When he fails to guess correctly, the kicker scores about 90 percent of the time. The penalty goal often decides a low-scoring game.
Studies have reported that soccer penalty kicks are admirably random, not displaying the excess alternation that’s seen in most sports. Why are soccer players good at randomizing when other athletes aren’t? It probably has to do with the long interval between successive penalty kicks. The kick is awarded to the opposing team when a player is guilty of bad behavior. Bad behavior is not exactly rare in soccer, but neither does it happen all the time. For a given player, penalty kicks may be days or weeks apart. It could be years before the player faces the same goalie in a penalty kick. For that reason, the kicker is likely to frame his choice as a one-shot event rather than as part of an ongoing interaction.
This isn’t to say that players don’t calculate odds. Netherlands goalie Hans van Breukelen kept a card index of penalty kickers with information about how they kicked. Germany’s Jens Lehmann kept a crib sheet in his sock. I imagine that players and coaches are primarily looking for habitual preferences, say that such-and-such-player kicked to the right seven of the last ten times. They don’t necessarily pay much attention to the pattern of choices in time. They may figure it’s irrelevant, as it seems to be.
The tail-wagging study I mentioned reported that mammals tend to move their bodies to the right when they see something they want. A friendly dog will tilt its head to the right. Humans put their head to the right when hugging and look to the right first when entering an unfamiliar room. This fact influences the design of store displays and the layout of supermarkets.
The University of Amsterdam group—Marieke Roskes, Daniel Sligte, Shaul Shalvi, and Carsten De Dreu—examined 204 penalty kicks in FIFA World Cup championships from 1982 through 2010. They found that when a goalie’s team was behind, he usually dived to the right (his right, the kicker’s left). This occurred 71 percent of the time.
When the team wasn’t behind, the right-left choices were evenly split. Kickers’ choices were also fairly close to even. Given that this seems to be rooted in biology, it probably applies to amateur games, too.
• When your team is winning (the other team is behind), have your team’s penalty kicker kick to the right (the goalie’s left).