The effect of goalkeepers adopting Muller-Lyer postures

Abstract

The posture that a goalkeeper assumes can influence perceptions of his or her size and the motor behavior of an opponent. Van der Kamp & Masters (2008) showed that postures that mimicked an amputated Muller-Lyer illusion in a wings-out/arms-up configuration resulted in larger estimates of goalkeeper height than a wings-in/arms-down configuration. Furthermore, when participants threw to score in a handball goal, the shots were placed further from the arms-up goalkeeper, presumably because he was thought capable of covering a greater area of the goal. We aimed to verify that throwing behaviour was related to (mis-)perceptions of goalkeeper height and, by association, goalkeeper reach. A 1.9 m animated representation of a goalkeeper was projected onto a blank screen. The goalkeeper was shown in an arms-up (45 degrees above horizontal), arms-out (horizontal), or arms-down (45 degrees below horizontal) posture. The 3 postures were each shown 10 times in a random order. For each presentation 34 participants made two estimates of the goalkeeper’s maximum static reach, which was defined as the position of middle finger of the goalkeeper in the arms-out posture. Estimates were made by aiming a laser pointer and throwing a ball. The horizontal displacements of the aiming and throwing estimates from the actual position of middle finger (75 cm from the midline of the body) were measured. For the horizontal displacement measure, there was no significant difference between aiming and throwing estimates (p > .05), but a significant effect of posture, F(2, 66) = 10.1, p <.01. Participants perceived the hand closer to the midline of the body in the arms-down posture (67.4 cm) than the arms-up posture (75.2 cm). The findings corroborate previous work in suggesting that the goalkeeper can influence perceptions of his maximum reach and the motor behaviour of an opponent by adopting illusory postures. Further investigations need to address whether the effects are also mediated by hand position or perceptions of arm length rather than body height.