Philip A Duke | Search PubMed

PubMed2003

Adaptation to vertical disparity induced-depth: implications for disparity processing.

Depth aftereffects produced by prolonged inspection of an object in depth can be mediated by monocular and binocular depth cues. The adapting mechanisms responsible for such effects have not yet been fully determined. Theories of binocular depth aftereffects typically posit a role of an adaptive horizontal disparity sensitive mechanism, implying multiple cue-specific mechanisms for depth aftereffects. Here we examined whether binocular depth aftereffects can be attributed to such a cue-specific mechanism. In Experiment 1 we did so using a technique allowing us to maintain horizontal disparities and vergence constant for our adaptation stimuli, whilst manipulating simulated depth by virtue of a vertical disparity induced-depth effect. We found that depth aftereffects were almost identical to those produced by adaptation to stimuli of equivalent depth produced by conventional horizontal disparity modulations. In Experiment 2, we examined depth aftereffects following adaptation to apparently frontal surfaces produced by different combinations of horizontal and vertical disparity modulations. Aftereffects were close to zero. These results suggest that binocular depth aftereffects are not due to adaptation of a horizontal disparity sensitive mechanism, and we argue that adaptation occurs at the level of a 3D shape sensitive mechanism derived from multiple cues. Experiment 3 was a control to examine whether the two types of adaptation stimuli in Experiment 1 were indeed perceptually the same, since in theory they may differ if vertical disparities influenced metric depth scaling. We found no evidence of this, and concluded that the two classes of stimuli used in Experiment 1, though consisting of very different patterns of disparity, were perceptually equivalent.

Adaptation, Physiological↗

PubMed2003

Monocular transparency generates quantitative depth.

Monocular zones adjacent to depth steps can create an impression of depth in the absence of binocular disparity. However, the magnitude of depth is not specified. We designed a stereogram that provides information about depth magnitude but which has no disparity. The effect depends on transparency rather than occlusion. For most subjects, depth magnitude produced by monocular transparency was similar to that created by a disparity-defined depth probe. Addition of disparity to monocular transparency did not improve the accuracy of depth settings. The magnitude of depth created by monocular occlusion fell short of that created by monocular transparency.

Adult↗

PubMed2003

Stereoscopic surface interpolation supports lightness constancy.

The human visual system has a remarkable ability to construct surface representations from sparse stereoscopic, as well as texture and motion, information. In impoverished displays where few points are used to define regions in depth, the brain often interpolates depth estimates across intervening blank regions to create a compelling sense of a solid surface. The set of experiments described here examined stereoscopic interpolation using a novel technique based on lightness constancy. The effectiveness of this method is notable because it stands as the only technique to date that unequivocally examines the perception of interpolated surfaces, and not surfaces inferred subjectively from depth information in the stimulus. Further, these data support the growing evidence that a primary function of the stereoscopic system is to define three-dimensional surface structure.

Adult↗