Exploring environments by hand or foot: Time-based heuristics for encoding distance in movement space.

In Experiment I, blindfolded observers judged (a) the distance of pathways felt by hand and (b) the straight-line distance between pathway endpoints inferred from such exploration.In Experiment 2, blindfolded observers made corresponding estimates after traversing similar pathways on foot.Pathways were explored under three different speeds.Under both manipulatory and ambulatory exploration, there was substantial length distortion of inferred distance: The straight-line distance was increasingly overestimated with increases in the length of the explored pathway.With manipulatory exploration, slower movements increased length distortion, but duration effects proved secondary to effects of spatial extent.For ambulatory exploration, no duration effects were obtained.Observers used time-independent heuristics, that is, a footstep metric for estimating the pathway actually travelled and a spatial imaging strategy for estimating the inferred line between pathway endpoints.The studies establish length distortion as a general phenomenon in movement space and identify its major causes as spatial rather than temporal.Substantial research in visual perception and cognition has investigated how an observer achieves a representation of the layout of objects in space and how that representation departs from veridicality (e.g., Gogel, 1978;Hirtle & Jonides, 1985;Moar & Bower, 1983; and see later discussion).In contrast, we know little about the representation of spatial layout by observers who are denied the use of sight.Theories of spatial representation frequently distinguish between large-and small-scale space.Note that size and scale are not considered synonymous.For example, according to Siegel (1981), distinctions in size (e.g., large, small) involve comparisons of space along some physical metric, for example, centimeters or meters.In contrast, distinctions in scale involve comparisons of the perceptual and motor mechanisms used.Acredolo (1981) articulated two major features of a largescale environment, based on a discussion by Ittelson (1973).First, a large-scale space encloses an observer; a small-scale space does not.Second, a large-scale environment is typically explored from multiple vantage points, and to this extent in-