"You must look at soccer as a game of pressure, " said Geir Jordet who teaches at the Norwegian Institute of Sport Sciences and has done extensive research on penalty kicks.

WSJ: Euro 2012: An Apologia for the Penalty Kick Shootout

Jordet's research, which includes the 35 Euro and World Cup matches that have been decided by penalty kicks since 1976, shows that no variable has a greater impact on scoring than the pressure.

WSJ: Euro 2012: An Apologia for the Penalty Kick Shootout

And then there's good old fashioned panic: In a 2009 study, Jordet found that players who approach the ball less than 0.2 seconds after the referee blows the whistle succeed on less than half of their kicks compared with players who take longer (they score on 80%).

WSJ: Euro 2012: An Apologia for the Penalty Kick Shootout