Open Loop Pointing in Virtual Environments

The two visual systems hypothesis is a powerful neuroanatomical model of the relationship between visual perception and motor action. The hypothesis claims that two independent streams of visual processing within the human brain maintain independent representations of surrounding space. A cognitive stream of visual processing maintains an allocentric map of space, while a sensorimotor stream of visual processing maintains an egocentric map of space. The interactions between these two spatial maps are believed to be responsible for an apparent dissociation between cognitive (non-motor) and sensorimotor responses in numerous artificial settings. Substantial evidence supports the two visual systems hypothesis, ranging from case studies of patients with brain damage to psychophysical studies of normal subjects in tasks that involve the presence of visual illusions. Because even the most advanced virtual reality systems can unintentionally synthesize visual display artifacts that resemble common visual illusions, the two visual systems hypothesis may be helpful in guiding the design and evaluation of usable interaction techniques for complex virtual reality applications. The hypothesis suggests that inherently cognitive classes of interaction techniques, such as vocal interaction and closed loop (with visual feedback) pointing, are subject to particular execution errors, while inherently motor classes of interaction techniques, such as open loop (no visual feedback) pointing, are not. This thesis describes an experimental investigation of open loop and closed loop pointing compared to voice-based input in a large-scale interactive display. Experimental results verify that the unintentional illusory errors that are predicted by the two visual systems hypothesis appear with the use of vocal interaction in the presence of a visual illusion known as the Roelofs Effect. Similar response errors were found in closed loop pointing, but there were comparatively fewer illusory errors in open loop pointing. An examination of lag (temporal delay in visual feedback) yielded evidence that lag may also reduce the illusory response errors. These findings support our claim that the two visual systems hypothesis can be influential in improving the usability of virtual reality applications.