Comparison of two indicators of perceived egocentric distance under full-cue and reduced-cue conditions

It has not been established that walking without vision to previewed targets is indeed controlled by perceived distance. To this end, we compared walking and verbal report as distance indicators, looking for a tight covariation in responses that would indicate control by a common variable. Targets from 79-500 cm away were presented under dark and well-lit conditions. Both verbal reports and walking indicated overestimation of near targets and underestimation of far targets under dark viewing conditions. Moreover, the finding that verbally reported distance plotted essentially as a single-valued function of walked distance and vice versa is evidence that both indicators were responding to the same internal variable, ostensibly perceived distance. In addition, binocular parallax, absolute motion parallax, and angular elevation were evaluated as distance cues, and only angular elevation exerted a targe influence on perceived distance.