Visually mismatched feedback within a head-mounted display affects a perceptual-motor but not a cognitive real world egocentric distance response

We describe an experiment in which mismatches between actual walking speed and visual indicators of the speed of self-motion within a head-mounted display (HMD) alter a perceptual-motor but not a cognitive indication of egocentric distance perception in the real world. We conducted a within-subject design experiment (pre- and post-test) that had four between subject conditions: 2 HMD feedback conditions (visually faster, visually slower) × 2 response measures in the real world (blind walking to previously viewed targets, verbal reports). While pre-tests revealed accurate real world direct blind walking performance, visually faster and slower post-tests showed an 11 undershoot and 17 overshoot, respectively. Verbal reports in the real world were approximately 81 of the actual distance both before and after HMD feedback. We previously found that verbal reports and blind walking in an HMD, which without feedback are both compressed, became near accurate after matched continuous visual feedback was given within the HMD. The same experience within the HMD had little or no effect on either real world blind walking or real-world verbal reports of distance (Mohler et al. 2006 APGV). The result from this previous experiment that both perceptual-motor and cognitive responses within the HMD were affected by feedback that was predominately perceptual-motor in nature suggests to us one of three explanations: (1) a common cognitive rule is applied across responses, (2) perceptual-motor and cognitive responses are adapted using different mechanisms producing similar changes, or (3) adaptation produces a general change in the perception of space. The current results showing a differential effect on two response measures in the real world, one perceptual-motor and the other cognitive, argues against an explanation exclusively involving changes in space perception and supports an account in which cognitive effects, perhaps combined with perceptual-motor adaptation, play a role