Abstract: Two-dimensional Titchener illusion pictures were used to examine the phenomena of the dissociation between perception and action in one-hand grasping and two-hand grasping situations. The effects of some important factors such as attention driven on the dissociation were explored. There were perception tasks and action tasks included in the present study. The former measured the size of the perceptual illusion, while the latter verified if the dissociation existed and its related factors were examined. During action tasks, the subjects’ action indexes, maximum grip apertures between their thumbs and index fingers, were recorded when the size of center circles were in fact the same or by perception. It was found that the actions of the left hand and right hand appeared dissociated with perception though they were all influenced by illusion to some extent in one-hand situation. The right hand was less influenced by illusion and clearly appeared dissociated while the results of the left hand were confused in two-hand situation. It was concluded that the dissociation existed, but it might be influenced by attention driven, attention-sharing strategies and the cooperative characteristics of the two hands.

Key words: dissociation between perception and action, Titchener illusion, driven by attention, maximum grip aperture