Objective but not subjective effect of height in a virtual slack-rope balance task

Ten young adults performed a balance task in a virtual environment projected via a head referenced head mounted display. The task constituted of crossing a canyon along a slack-rope, positioned at three different heights (2,50 & 100 meters above a river) and in three velocities (slow, medium & fast). Time (s) of crossing of the canyon was measured as the outcome measure. The results show that the time was directly dependent upon the height of the rope above the river, i.e., the higher the rope, the slower the time, in the fast (F(2,18)=5.24, p=0.016) and in the slow (F_(2,18)=8.469, p=0.003) velocities. However, subjectively, all participants reported they felt no difference in their own performance in the different heights. Thus, this gap between the objective performance and the subjective perception of performance may indicate a height-time trade-off in performing a virtual balance task.