Ease of hand rotation during active exploration of views of a 3-D object modulates view generalization.

Active exploration of views of 3-D objects by manually controlling a device, such as a trackball, facilitates subsequent object recognition, suggesting that motor simulation contributes to object recognition. Further, biomechanical constraints, such as range of hand rotation, can affect mental rotation. Thus, the ease with which an object can be rotated by hand may modulate the facilitative effect active exploration through manual control has on object recognition. In our experiment, participants performed two sessions of a view-matching task, with a learning task administered between the two. In the learning task, one group of participants (active group) viewed and explored a novel 3-D object using their hand to rotate a handle attached to a cathode-ray tube monitor. The other group (passive group) observed on the monitor a replay of the movements of the 3-D object as manipulated by an active-group participant. Active-group participants were interviewed to determine the direction they found easiest to rotate their hand. The view-generalization performances were compared between the pre and post sessions. Although we observed a facilitative effect on the view-matching process in both groups, the active group exhibited view-dependent facilitation. The view-generalization range of the active group in the post-session was asymmetric in terms of the rotation direction. Most intriguingly, for most participants, this asymmetric change corresponded to the direction that afforded the easiest hand rotation (ulnar deviation). These findings suggest that the object-recognition process can be affected by ease of hand rotation, which is based on the biomechanical constraints of the wrist joint.