Penalty kicks are nearly universally reviled among soccer fans, yet they remain an important part of the game. The sport is so exhausting that extending it beyond 30 minutes of extra time in a playoff game could be dangerous for the players. Typically in playoff or championship matches, tie games get decided by a penalty kick competition.
But penalty kicks offer such an advantage to the shooter that it often seems like dumb luck when a goalkeeper manages to make a save. The usual strategy is simply to dive randomly to the left or right, and hope you guessed right. Why not just flip a coin to decide who wins the match? Chris at Mixing Memory has found a study suggesting that the position of the goalkeeper just before the shot can indeed affect the shooter:
They found that in almost all instances (96%), the goalkeeper stood just slightly (and I mean just slightly) off center, creating a difference between the distance of the goalie from the two goal posts of about 9.95 centimeters, which amounts to a difference between the areas to the right and left of the goal keeper of about 2.9% of the total area of the goal. The side to which the goalie stood did not, however, influence the side to which the goalie dove as the ball was kicked. So goalies didn’t seem to be aware of their position. However, when they looked at whether penalty takers were aware of the position of the goal keeper, they found that 103 out of 174 (I’m not sure what happened to the other 26 kicks) were to the side of the goal keeper with more space. So the position of the goal keeper does appear to affect the direction of the kick on a (statistically) significant percentage of penalty kicks. Penalty takers are, then, aware of the goalie’s position.
200 kicks were studied, and 103 out of 174 went to the side with the most space between the keeper and the post. (What happened to the other 26 kicks? I’d guess they were straight at the keeper.) A separate series of experiments confirmed these results: though neither kicker nor keeper is aware that the keeper could be biased by as much as 3 percent to one side, more kicks went toward the side with more space.
The researchers suggest that keepers could use this subtle advantage to influence the direction of kicks, but Chris begs to differ:
Yeah, a lot of good that knowledge does us. If we were soccer coaches, and wanted to use this research, we’d quickly find that it wouldn’t help us a bit. Kickers are obviously already utilizing their ability to detect to which side of center the goalie is standing, and goalies seem to be unable to notice their position relative to the center, so they can’t use it to decide in which direction they should dive. ut hey, some psychologists got to watch a bunch of penalty kick videos, and I got to write a post about it, so it’s not a complete waste.
I’m not sure I buy that argument. Perhaps through extended experimentation, psychologists could devise a method by which goalkeepers could recognize the direction in which they are biased, thus gaining an advantage! Of course, such a project would require watching even more soccer games….