Effect of Visuo-Motor Co-location on 3D Fitts' Task Performance in Physical and Virtual Environments

Given the ease that humans have with using a keyboard and mouse in typical, non-colocated computer interaction, many studies have investigated the value of co-locating the visual field and motor workspaces using immersive display modalities. Significant understanding has been gained by previous work comparing physical tasks against virtual tasks, visuo-motor co-location versus non-colocation, and even visuo-motor rotational misalignments in virtual environments (VEs). However, few studies have explored all of these paradigms in context with each other and it is difficult to perform inter-study comparisons because of the variation in tested motor tasks. Therefore, using a stereoscopic fish tank display setup, the goal for the current study was to characterize human performance of a 3D Fitts' point-to-point reaching task using a stylus-based haptic interface in the physical, co-located/non-colocated, and rotated VE visualization conditions.Five performance measures - throughput, initial movement error, corrective movements, and peak velocity - were measured and used to evaluate task performance. These measures were studied in 22 subjects (11 male, 11 female, ages 20-32) performing a 3D variant of Fitts' serial task under 10 task conditions: physical, co-located VE, non-colocated VE, and rotated VEs from 45-315° in 45° increments. All performance measures in the co-located VE were expected to reflect significantly reduced task performance over the real condition, but also reflect increased performance over the non-colocated VE condition. For rotational misalignments, all performance measures were expected to reflect highest performance at 0°, reduce to lowest performance at 90° and rise again to a local maximum at 180° (symmetric about 0°). All performance measures showed that the co-located VE condition resulted in significantly lower task performance than the physical condition and higher mean performance than the non-colocated VE condition, but the difference was not statistically significant. Also, rotation misalignments showed that task performance were mostly reduced to minimums at 90°, 135°, and 225°. We conclude that co-located VEs may not significantly improve point-to-point reaching performance over non-colocated VEs. Also, visual rotations of ±45° affected throughput, efficiency, peak velocity, and initial movement error, but the number of corrective movements were not affected until ±90°.