An investigation into the coordinated mechanisms of reaching and grasping during prehension in an illusion paradigm.

2003 Fiscal Year Final Research Report Summary

• Project/Area Number: 13610078
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 実験系心理学
• Research Institution: NIIGATA UNIVERSITY
• Principal Investigator: KUDOH Nobuo NIIGATA UNIVERSITY, Faculty of humanities, Associate Professor, 人文学部, 助教授 (10234452)
• Project Period (FY): 2001 – 2003
• Keywords: prehension / Mueller-Lyer illusion / reaching / manual estimation / frame of reference

Research Abstract

We derive the spatial structure of the surrounding physical space through the visual system, and thereby construct an internal representation of the external environment. Since our spatial behaviors such as reaching, grasping, and walking are tightly coupled to visual information, there have been numerous studies of the relationship between visual perception and action. Aglioti et al.(1995) have investigated the effects of the Ebbinghause illusion in perception and action. In this illusion, two identical discs can be perceived as being different in size when one is surrounded by an annulus of smaller circles and the other is surrounded by an annulus of larger circles. They found that when subjects were required to pick up one of the discs, their grip aperture during prehension were insensitive to the illusions that strongly bias visual perception. However, recent studies concerning illusion effects on action seems to be inconsistent with these original findings. The aim of this study w as to investigate a dissociation between perception and action using a Mueler-Lyer illusion. In Experiment. 1 of this study, subjects were required to reach for each vertex of a Mueller-Lyer and control figures. Reaching was executed 0 sec(0 sec delay condition) and 5 sec(5 sec delay condition) after the light was switched off. The reaching errors in the 5 sec delay condition were biased in the direction of the illusion, while those in the 0 sec condition were not affected by the illusion. In Experiment 2,subjects were required to match the length of the shaft of the Mueller-Lyer and control figures by opening their thumb and index fingers(manual estimation). The results showed that, finger aperture was strongly affected by the illusion but no significant difference in finger aperture was observed between the 0 sec and 5 sec delay conditions. These results suggest that the action systems underlying the control of reaching not only operate on-line but also within egocentric frames of reference, and information about the length and the spatial location might be separately represented.