Bimanual control strategies

Two tasks (A and B) were designed which required participants to sequentially move through four target positions in a Lissajous display. Task A was designed so that participants could complete the task using either unimanual or bimanual control strategies. Task B was designed so that participants could complete the task using relatively simple or more complex bimanual control strategies. The purpose of this study was to determine which control strategy the participant utilises to complete the two tasks when Lissajous displays are provided and to determine the degree to which the size of the targets influences the control strategy chosen under these conditions. The movement amplitude between two adjacent targets and the target size resulted in an Index of Difficulty (ID) of 2 and 4 for each task. For both tasks, participants practised 15 trials (30 s per trial) for each ID and then was administered a test trial. The results for both Tasks A and B indicated that the ID2 condition resulted in a circular path, whereas the ID4 condition resulted in a straight-line path on the Lissajous plot. This suggests that at the low ID condition participants produced a continuous 1:1 with 90° phase offset bimanual coordination pattern. At the high ID condition, the participants consistently chose to switch to a more stable unimanual left and right movements in Task A and to transition between in-phase and anti-phase bimanual coordination patterns in Task B. In addition, both limbs’ movements were more harmonic in the low ID condition than in the high ID condition.

Evaluating Control Schemes for the Third Arm of an Avatar

Recent research on immersive virtual environments has shown that users can not only inhabit and identify with novel avatars with novel body extensions, but also learn to control novel appendages in ways beneficial to the task at hand. But how different control schemas might affect task performance and body ownership with novel avatar appendages has yet to be explored. In this article, we discuss the design of control schemas based on the theory and practice of 3D interactions applied to novel avatar bodies. Using a within-subjects design, we compare the effects of controlling a third arm with three different control schemas (bimanual, unimanual, and head-control) on task performance, simulator sickness, presence, and user preference. Both the unimanual and the head-control were significantly faster, elicited significantly higher body ownership, and were preferred over the bimanual control schema. Participants felt that the bimanual control was significantly more difficult than the unimanual control, and elicited less appendage agency than the head-control. There were no differences in reported simulator sickness. We discuss the implications of these results for interface design.