Visually directed walking to briefly glimpsed targets is not biased towardfixation location

When observers indicate the magnitude of a previously viewed spatial extent by walking without vision to each endpoint, there is little evidence of th e perceptual collapse in depth associated with some other methods (eg visua l matching). One explanation is that both walking and matching are perceptu ally mediated, but that the perceived layout is task-dependent. In this vie w, perceived depth beyond 2-3 m is typically distorted by an equidistance e ffect, whereby the egocentric distances of nonfixated portions of the depth interval are perceptually pulled toward the fixated point. Action-based re sponses, however, recruit processes that enhance perceptual accuracy as the stimulus configuration is inspected. This predicts that walked indications of egocentric distance performed without vision should exhibit equidistanc e effects at short exposure durations, but become more accurate at longer e xposures. In this paper, two experiments demonstrate that in a well-lit env ironment there is substantial perceptual anisotropy at near distances (3-5 m), but that walked indications of egocentric distance are quite accurate a fter brief glimpses (150 ms), even when the walking target is not directly fixated. Longer exposures do not increase accuracy. The results are clearly inconsistent with the task-dependent information processing explanation, b ut do not rule out others in which perception mediates both walking and vis ual matches.