This experiment examined whether the impact of pictorial illusions during the execution of goal-directed reaching movements
is attributable to ocular motor signaling. We analyzed eye and hand movements directed toward both the vertex of the Müller–Lyer
(ML) figure in a closed-loop procedure. Participants pointed to the right vertex of a visual stimulus in two conditions: a
control condition wherein the figure (in-ML, neutral, out-ML) presented at response planning remained unchanged throughout
the movement, and an experimental condition wherein a neutral figure presented at response planning was perturbed to an illusory
figure (in-ML, out-ML) at movement onset. Consistent with previous work from our group (Heath et al. in Exp Brain Res 158:378–384,
2004; Heath et al. in J Mot Behav 37:179–185,
2005b), action-bias present in both conditions; thus illusory bias was introduced into during online control. Although primary
saccades were influenced by illusory configurations (control conditions; see Binsted and Elliott in Hum Mov Sci 18:103–117,
1999a), illusory bias developed within the secondary “corrective” saccades during experimental trials (i.e., following a veridical
primary saccade). These results support the position that a unitary spatial representation underlies both action and perception
and this representation is common to both the manual and oculomotor systems.
Keywords Illusion - Saccade - Pointing - Müller–Lyer - Closed-loop