Visually perceived eye level: Changes induced by a pitched-from-vertical 2-line visual field.

Abstract

The physical elevation corresponding to visually perceived eye level (VPEL) changes linearly with the pitch of a visual field. Deviations from true eye level average more than 0.5 times the angle of pitch over a 65 degrees pitch range. A visual field consisting of 2 dim, isolated vertical lines in darkness is more than 4/5 as effective as that of a complexly structured visual field; 2 horizontal lines have a small and inconsistent effect. Differences in influence on VPEL between pitched-from-vertical and horizontal lines were predicted from an analysis that extracted differences in retinal perspective resulting from changes in pitch. The Great Circle Model (GCM), based on a spherical approximation to the erect, stationary eye, predicts the present results and results of 8 other sets of experiments. The model treats the influence of a single line on VPEL as systematically related to the elevation of the intersection between the great circle containing the image of the line and the central vertical retinal meridian; generalized GCM combines visual inputs with inputs from the body-referenced mechanism and maps onto the central nervous system.

Influence of gaze elevation on estimating the possibility of passing under high obstacles during body tilt

“…This finding might lead to a new and hybrid reference frame, corresponding to a sustained intermediate state between a geocentric reference frame normally required to adequately perform the task, and a disturbing egocentric reference frame. Successive transformations of coordinates required to perform the task (Matin and Li 1992;Stoper and Cohen 1989) may account for the influence of one reference frame to another.…”

“…earth-based) systems of coordinates, including the direction of gravity and the physical horizon (Howard 1982). Gaze elevation may have an influence on geocentric estimates because information about the position of the target on the retina and information about the position of the eye in the head are required for such perceptual tasks (Matin and Li 1992;Stoper and Cohen 1989). By successive transformations of coordinates, a stable map can be maintained between spatial localization, spatial orientation, and physical space (Matin and Li 1995).…”

The field dependence/independence cognitive style does not control the spatial perception of elevation

“…(2) The subsequent stages of processing are carried out separately by different higher order processes in different cortical regions. Such a model for the processing of VPV and VPELcommon lower level processing and separate higher level processing in the cerebral cortex-accounts well for the original requirement of two higher order mechanisms to account for the basic results with one-line and two-line stimuli with VPV and VPEL discriminations (Matin & Li, 1992a, 1992b, 1994a, 1994b, as well as for the more recent correlations between the two discriminations for the experiments with one-line and two-line inducers and for the experiments with the frame, without invoking a still higher common level of processing that involves cognitive restructuring (Shavit et al, 2004).…”

“…However, there is a second possible basis for the correlations between VPV and VPEL measures: The relation between VPEL and the orientation of the one-line or twoline inducers is nearly linear, as is the relation between VPV and the orientation of the one-line or two-line inducers (Li & Matin, 2005a, 2005cMatin & Li, 1992a, 1992b, 1994a, 1994b. These near-linear relations have been well fitted by straight lines with slopes that are invariably less than the slope of 1.00 corresponding to the slope for which there is a 1:1 relation between the discrimination measure-VPEL or VPV-and line orientation.…”

“…For such dimensions, the theoretical approach to FDI would suggest that analogous manipulations of the inducing field might produce effects that are mediated by the same differences among individuals in cognitive style as those that have been suggested to be significant for the perception of verticality. The perception of elevation is such a dimension; large systematic effects on the setting of a visual target to appear at eye level (visually perceived eye level [VPEL] discrimination) are generated by changes in the pitch of a visual field (Hudson, Li, & Matin, 2000;Li, Dallal, & Matin, 2001;Li & Matin, 1996, 1998Matin & Fox, 1986Matin & Li, 1992a, 1992b, 1994a, 1994b, 1995, 1999, 2000Poquin, Ohlmann, & Barraud, 1998;Post, Teague, Welch, & Hudson, 2003;Post & Welch, 1996;Post, Welch, & Clark, 2000;Stoper & Cohen, 1989; these effects are nearly linear with visual pitch over a range between 40º and 30º. Both setting a target to VPEL in the presence of a pitched visual field and setting a rod to appear vertical in the presence of a roll-tilted visual field-the visually perceived vertical (VPV) discrimination employed in the RFT-involve significant discordances between visual and gravitational stimulation, although in different spatial dimensions (see Figure 1).…”