title: A Judd illusion in far-aiming: evidence of a contribution to action by vision for perception.
abstract: The present study addresses the role of vision for perception in determining the location of a target in far-aiming. Participants (N = 12) slid a disk toward a distant target embedded in illusory Judd figures. Additionally, in a perception task, participants indicated when a moving pointer reached the midpoint of the Judd figures. The number of hits, the number of misses to the left and to the right of the target, the sliding error (in mm) and perceptual judgment error (in mm) served as dependent variables. Results showed an illusory bias in sliding, the magnitude of which was comparable to the bias in the perception of target location. The determination of target location in far-aiming is thus based on relative metrics. We argue that vision for perception sets the boundary constraints for action and that within these constraints vision for action autonomously controls movement execution, but alternative accounts are discussed as well.
authors.affiliation: Faculty of Human Movement Sciences, Research Institute MOVE, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands. j_van_der_kamp@fbw.vu.nl
authors.forename: John
authors.initials: J
authors.lastname: van der Kamp
authors.forename: Hemke
authors.initials: H
authors.lastname: van Doorn
authors.forename: Rich S W
authors.initials: RS
authors.lastname: Masters
mesh_terms: D000704:Analysis of Variance; D006801:Humans; D007088:Illusions; D009043:Motor Activity; D009483:Neuropsychological Tests; D011597:Psychomotor Performance; D013647:Task Performance and Analysis; D014796:Visual Perception; D055815:Young Adult