Subject-coincident coordinate systems and sustained motions

Abstract

Vestibular research on human perception of self-motion and orientation generally uses the head-based coordinate system standardized by Hixson, Niven, and Correia (1966) for specifying accelerations of the subject. This paper expands the head-based system to include velocities, thereby incorporating both the visual and vestibular systems, and formally defines the resulting concept of asubject-coincident coordinate system. By capturing the organism's vantage point during self-motion, subject-coincident systems give a natural framework for studying the relationship between stimulus, physiology, and perception; however, the essential approach differs from that familiar in traditional physics, so the necessary equations of motion are developed here. In addition, these equations are used to investigate the set ofsustained motions, those motions that can be sustained over a period of time. These motions can cause disorientation and misperception of motion because of saturation or adaptation of the human sensory receptors. The results on sustained motions are summarized in a complete categorization of the set of sustained motions.