Ball Bearings - Investigating the effect of lasting familiar size representations on prehensile movement using tennis balls

Abstract

This study was designed to examine whether the learned pictorial depth cue of familiar size is a constantly stored artefact. The attempt was to distinguish whether the familiar size effect occurs only after recent interaction, or if the representation resides in a longer term memory base. To do this a commercially made, but largely unknown, oversized tennis ball (type III) was used as the perturbation stimulus (probe ball), amongst an array of filler balls. Filler balls were presented at 6 distances, but the probe ball at only 2 familiar-size-specified distances. 26 participants were recruited, 13 tennis ‘experts’ who played tennis a minimum of once a week, and 13 controls who have never played tennis, or have not played tennis for a substantial period of time. If the familiar size effect prevailed, it was hypothesised that the expert group would under-reach to the perturbed stimulus, under the false impression that it was a ‘standard’ tennis ball. Analysis of participants’ reaching and grasping movements to filler balls allowed creation of regression equations used to predict reaching and grasping behaviour to the probe ball. There were no significant differences from predicted for either group in terms of distance reached, or maximum grip aperture formed. There was a significant effect of group on the peak velocity achieved with experts faster than predicted, and controls slower than predicted, at the near presentation distance, and the opposite pattern at the far presentation distance. This study did not find evidence that the familiar size effect prevailed as a lasting representation when no recent interaction is present. Various reasons are proposed for why this might be the case.