VIRTUAL EYES CAN REARRANGE YOUR BODY - ADAPTATION TO VISUAL DISPLACEMENT IN SEE-THROUGH, HEAD-MOUNTED DISPLAYS

Among the most critical issues in the design of immersive virtual envi ronments are those that deal with the problem of technologically induc ed intersensory conflict and one of the results, sensorimotor adaptati on. An experiment was conducted to support the design of a prototype s ee-through, head-mounted display (HMD). When wearing video see-through HMDs in augmented reality systems, subjects see the world around them through a pair of head-mounted video cameras. The study looked at the effects of sensory rearrangement caused by a HMD design that displace d the user's ''virtual'' eye position forward (165 mm) and above (62 m m) toward the spatial position of the cameras. The position of the cam eras creates images of the world that are slightly downward and inward from normal. Measures of hand-eye coordination and speed on a manual pegboard task revealed substantial perceptual costs of the eye displac ement initially, but also evidence of adaptation. Upon first wearing t he video see-through HMD, subjects' pointing errors increased signific antly along the spatial dimensions displaced (the y dimension, above-b elow the target, and z dimension, in front-behind the target). Speed o f performance on the pegboard task decreased by 43% compared to baseli ne performance. Pointing accuracy improved by approximately 33% as sub jects adapted to the sensory rearrangement, but it did not reach basel ine performance. When subjects removed the see-through HMD, there was evidence that their hand-eye coordination had been altered. Negative a ftereffects were observed in the form of greater errors in pointing ac curacy compared to baseline. Although these aftereffects are temporary , the results may have serious practical implications for the use of v ideo see-through HMDs by users (e.g., surgeons) who depend on very acc urate hand-eye coordination.