Authors: Anne Brec’hed Le Séac’h Patrice Senot Joseph McIntyre
Publish Date: 2009/12/19
Volume: 201, Issue: 4, Pages: 653-662
Abstract
When programming movement one must account for gravitational acceleration This is particularly important when catching a falling object because the task requires a precise estimate of timetocontact Knowledge of gravity’s effects is intimately linked to our definition of ‘up’ and ‘down’ Both directions can be described in an allocentric reference frame based on visual and/or gravitational cues or in an egocentric reference frame in which the body axis is taken as vertical To test which frame humans use to predict gravity’s effect we asked participants to intercept virtual balls approaching from above or below with artificially controlled acceleration that could be congruent or not with gravity To dissociate between these frames subjects were seated upright trunk parallel to gravity or lying down body axis orthogonal to the gravitational axis We report data in line with the use of an allocentric reference frame and discuss its relevance depending on available gravityrelated cues
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