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 large influence on perceived distance.

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A number of studies have resulted in the finding of a 3-D perceptual anisotropy, whereby spatial intervals oriented in depth are perceived to be smaller than physically equal intervals in the frontoparalleI plane. In this experiment, we examined whether this anisotropy is scale invariant. The stimuli were L shapes created by two rods placed flat on a level grassy field, with one rod defining a frontoparallel interval, and the other, a depth interval. Observers monocularly and binocularly viewed Lshapes at two scales such that they were projectively equivalent under monocular viewing. Observers judged the aspect ratio (depth/width) of each shape. Judged aspect ratio indicated a perceptual anisotropy that was invariant with scale for monocular viewing, but not for binocular viewing. When perspective is kept constant, monocular viewing results in perceptual anisotropy that is invariant across these two scales and presumably across still larger scales. This scale invariance indicates that the perception of shape under these conditions is determined independently of the perception of size.In recent years, a number of experimental studies have shown that, even under full-cue viewing, there is a clear anisotropy of perceived 3-D shape, with spatial intervals having a significant depth component appearing shorter than equal lengths oriented within a frontoparallel plane (Amorim, Loomis, & Fukusima, 1998; Baird & Biersdorf, 1967;Levin & Haber, 1993; Loomis, Da Silva, Fujita, & Fukusima, 1992;Norman, Todd, Perotti, & Tittle, 1996;Ribeiro-Filho, Fukusima, & Da Silva, 1995;Tittle, Todd, Perotti, & Norman, 1995;Todd, Tittle, & Norman, 1995;Toye, 1986;Wagner, 1985;Yang, Wade, & Proffitt, 1997); these recent studies confirm earlier studies showing systematic misperception of2-D shapes viewed with large values of slant under full cues (e.g., Beck & Gibson, 1955;Joynson & Newson, 1962;Kaiser, 1967;Wallach & Moore, 1962; see Sedgwick, 1986, for a review of much of this earlier work).It might be thought that this anisotropy of perceived 3-D shape is the consequence of some compressive nonlinearity between physical and perceived egocentric distance; such a nonlinear psychophysical mapping would imply, for instance, that depth intervals on the ground surface! would be seen as increasingly foreshortened rel- ative to frontoparallel intervals, the more distant the intervals are from the observer. Evidence for such a compressive nonlinearity has been reported in a number of studies (e.g., see review by Sedgwick, 1986); in particular, Gilinsky (1951) found that perceived distance was a hyperbolic function of physical distance with an asymptotic perceived distance of29 m. However, the depth scaling literature as a whole is equivocal about whether the psychophysical mapping is compressively nonlinear, with other studies suggesting that the mapping is linear and still others suggesting that perceived distance might even be an accelerating function of physical distance (see reviews by Baird, 1970; Da Silva, 1985;Sedgwick, 1986). Moreover, o...

D. R. Proffitt and colleagues (e. g., D. R. Proffitt, J. Stefanucci, T. Banton, & W. Epstein, 2003) have suggested that objects appear farther away if more effort is required to act upon them (e.g., by having to throw a ball). The authors attempted to replicate several findings supporting this view but found no effort-related effects in a variety of conditions differing in environment, type of effort, and intention to act. Although they did find an effect of effort on verbal reports when participants were instructed to take into account nonvisual (cognitive) factors, no effort-related effect was found under apparent-and objective-distance instruction types. The authors' interpretation is that in the paradigms tested, effort manipulations are prone to influencing response calibration because they encourage participants to take nonperceptual connotations of distance into account while leaving perceived distance itself unaffected. This in no way rules out the possibility that effort influences perception in other contexts, but it does focus attention on the role of response calibration in any verbal distance estimation task. Keywordsegocentric distance perception; effort; calibration; visual perception; instruction type Space perception researchers commonly encounter people who say, "You should study memy distance perception is terrible!" In experimental settings, however, the average participant can demonstrate remarkably good distance perception by walking accurately without vision to objects initially seen at distances up to 22 m or more (e. g., Loomis, Da Silva, Fujita, & Fukusima, 1992;Rieser, Ashmead, Talor, & Youngquist, 1990;Thomson, 1980, among a host of others). Informal discussion often reveals that people directly equate "poor distance perception" with their sense of unfamiliarity with assigning numbers to distances. Researchers, on the other hand, typically do not conceive of perceived distance as being so narrowly tied to one specific type of behavioral response. In fact, researchers have used a variety of behavioral methods to measure perceived distance in addition to blindfolded walking and verbal reports (see Loomis, Da Silva, Philbeck, &Fukusima, 1996, and Da Silva, 1985, for reviews). This illustrates that nonspecialists may have very different interpretations of "distance" and NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript "perceived distance" than researchers do. This article explores some possible conceptualizations of distance and their implications for space perception research.For researchers, perceived egocentric distance (or simply perceived distance) is a representation of the distance between oneself and an object. Some previous models of visual space perception (e.g., Foley, 1991;Gogel, 1990;Landy, Maloney, Johnson, & Young, 1995) have conceived of perceived distance as the result of a series of processing stages: taking a set of stimulus cues as inputs, weighting these cues according to their reliability, and then combining the resulting weighted st...

Three experiments investigated auditory distance perception under natural listening conditions in a large open field. Targets varied in egocentric distance from 3 to 16 m. By presenting visual targets at these same locations on other trials, we were able to compare visual and auditory distance perception under similar circumstances. In some experimental conditions, observers made verbal reports of target distance. In others, observers viewed or listened to the target and then, without further perceptual information about the target, attempted to face the target, walk directly to it, or walk along a two-segment indirect path to it. The primary results were these. First, the verbal and walking responses were largely concordant, with the walking responses exhibiting less between-observer variability. Second, different motoric responses provided consistent estimates of the perceived target locations and, therefore, of the initially perceived distances. Third, under circumstances for which visual targets were perceived more or less correctly in distance using the more precise walking response, auditory targets were generally perceived with considerable systematic error. In particular, the perceived locations of the auditory targets varied only about half as much in distance as did the physical targets; in addition, there was a tendency to underestimate target distance, except for the closest targets.Spatial hearing is concerned with the localization of sound sources and reflecting surfaces. In this paper, our focus is on the localization of sound sources. The egocentric location of a source is usually specified in these following coordinates: azimuth (compass direction with respect to the facing direction ofthe head), elevation, and distance. The vast majority of studies on the localization of sources has been concerned with directional hearing; only a few studies have dealt with auditory distance perception. Now, however, the emerging technology of virtual acoustics is promoting considerable interest in the topic. Virtual acoustic displays have considerable promise as interfaces between humans and computers in which "virtual" or "spatialized" sound is used to represent real and virtual environments and abstract data structures