Stereoscopic Depth Constancy Depends on the Subject's Task

Abstract

Under identical viewing conditions, observers made two types of judgement about the shape of stereoscopically defined surfaces: one required an estimate of viewing distance for correct performance (e.g. setting the depth of a hemi-cylinder to equal its half-height or a dihedral angle to 90 deg), the other did not (matching the depth of, for example, sinusoidal corrugations or hemi-cylinders presented at two distances). Depth constancy for the two types of task was about 75% and 100%, respectively. We argue that observers may use a simple "direct" strategy to perform the depth matching task rather than constructing and comparing a metric representation of each surface.

Stereoillusory motion concomitant with lateral head movements

“…As expected, perceived depth was greater in the 20¢ of arc than in the 10¢ of arc disparity condition, and, furthermore, perceived depth for each disparity condition increased as a function of viewing distance. The latter result is consistent with those previously reported in the literature relevant to stereoscopic depth constancy (e.g., Glennerster, Rogers, & Bradshaw, 1996;Ono & Comerford;1977;Patterson et al, 1995;Ritter, 1977Ritter, , 1979Shimono, Nakamizo, & Tsuchida, 1990). The depth data were submitted to a two-way repeated measures (4 disparity 3 3 viewing distance) ANOVA.…”

Toward a new theory of stereopsis.

“…In order to perceive the values d 1 and d 2 , the observer must have information about the egocentric distance of the object (D) to scale the relative depth information and size specified at the retina (Glennerster, Rogers & Bradshaw, 1996;Landy et al, 1995;Kaufman et al, 2006). If cues to egocentric distance are available, the 3-D shape, scale and absolute depth values can all, in principle, be derived ( Figure 4B).…”

“…There have been several propositions that the perception of 3-D space consists of multiple distinct or dissociated representations; related to stages of information processing, or tied to specific adaptive roles. For example, some authors have suggested that depth processing proceeds in a constructive fashion, from the initial detection of depth order, to the derivation of quantitative relative depth relations, to the final derivation of absolute depth values (Glennerster, Rogers & Bradshaw, 1996). They proposed that different visual functions may have access to different stages of this processing.…”

“…One possibility is that these tasks either partially or fully tap into representations different from those driving the perception of global surface/object shape. Different depth judgement tasks are thought to access different aspects of depth representation or levels of processing (Koenderink and van Doorn, 2003;Glennerster, Rogers & Bradshaw, 1996). For example Di Luca, Domini & Caudek (2010) found that judgements of curvature, local slant and depth separation between points on the same surface were not metrically consistent.…”

Direct perception of global invariants is not a fruitful notion

“…The selection starts even earlier if one considers the movements we make to obtain the information. Separate independent processing for different judgments can result in substantial conf1icts between them (Abrams & Landgraf 1990;Glennerster et al 1996;Mack et al 1985). Nevertheless, the separation seems be so complete that we even fail to notice conflicts between attributes when the conflicts themselves could give us valuable additional information (Brenner & Damme 1999;Brenner & Landy 1999).…”