Abstract
When grasping an object, the opening between the fingertips (grip aperture) scales with the size of the object. If an object changes in size, the grip aperture has to be corrected. In this study, it was investigated whether such corrections would influence the perceived size of objects. The grasping plan was manipulated with a preview of the object, after which participants initiated their reaching movement without vision. In a minority of the grasps, the object changed in size after the preview and participants had to adjust their grasping movement. Visual feedback was manipulated in two experiments. In experiment 1, vision was restored during reach and both visual and haptic information was available to correct the grasp and lift the object. In experiment 2, no visual information was provided during the movement and grasps could only be corrected using haptic information. Participants made reach-to-grasp movements towards two objects and compared these in size. Results showed that participants adjusted their grasp to a change in object size from preview to grasped object in both experiments. However, a change in object size did not bias the perception of object size or alter discrimination performance. In experiment 2, a small perceptual bias was found when objects changed from large to small. However, this bias was much smaller than the difference that could be discriminated and could not be considered meaningful. Therefore, it can be concluded that the planning and execution of reach-to-grasp movements do not reliably affect the perception of object size.
Highlights
Sensory information can be used to guide our movements and to perceive the world around us
Grasping an object will give haptic information about object size which can be optimally integrated with vision to obtain an accurate percept of object size [2]
In Experiment 2, no visual information was available and corrections could only be based on haptic information
Summary
Sensory information can be used to guide our movements and to perceive the world around us. When grasping an object, visual information about object size can be used to scale the opening between the fingertips (grip aperture) to the size of the object [1]. Grasping an object will give haptic information about object size which can be optimally integrated with vision to obtain an accurate percept of object size [2]. The dualstream theory, it has been suggested that processing of visual information for guiding actions and perception are separated in two streams in the brain [3].
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