Pitching people with an inversion table: Estimates of body orientation are tipped as much as those of visual surfaces.

Abstract

In the current work we investigate people's perception of their own body tilt in the pitch direction. In Experiment 1, we tilted people backward at 1 of 5 different randomly assigned angles using an inversion table. People significantly overestimated the angle at which they were tilted backward at angles from 8° to 45°. The slope of the plotted average overestimates had a gain of 1.46, fitting nicely with previously reported gains of verbal overestimates of visually perceived slant of natural outdoor geographically oriented slopes as well as man-made wooden slopes within and outside of reach in the laboratory. In Experiment 2, we showed participants a 45° line and asked them to indicate when they were positioned at that orientation. Participants again significantly overestimated the angle at which they were tilted backward. This extends work showing that a scale-expanded theory of visual space is multisensory, results in equivalent estimates for both verbal and nonverbal/nonnumeric methods, and can now be expanded to include the perceived orientation of one's own body.