The Effects of the Müller-Lyer Goalkeepers’ Illusion on Perceptions and Location of Throws of Penalty Takers

The main aim of the present study was to investigate whether the goalkeepers’ postures that mimic the Müller–Lyer illusion can influence penalty-takers’ perceptions and the location of throws. A representation of a goalkeeper was projected onto a blank screen (without goalposts and crossbar). The goalkeeper was displayed in arms-up (45 degrees above horizon), arms-out (horizontal, as control), and arms-down (45 degrees below horizon) postures. Participants (11 young male handball players) performed two tasks. They stood in front of the screen at a distance of 5 m and observed the goalkeeper displayed in one of the three postures. The participants were asked either to throw a tennis ball, or aim a laser pointer at, the horizontal position of the goalkeeper’s hand. The horizontal distances of throwing and aiming locations were measured from the midline of the body of the goalkeeper model. The goalkeeper postures affected the locations of the throwing and aiming. The participants’ aiming and throwing tasks were found to be significantly farther from and closer in the arms-up and arms-down postures compared with the arms-out posture respectively. The experiment demonstrated that a goalkeeper adopting Müller–Lyer postures can influence his opponent’s perception of maximum reach and his motor behavior.