Visual Attention and Cognition W.H. Zangemeister, H.S. Stiehl and C. Freksa (Editors) 10 1996 Elsevier Science B.V. All rights reserved. EXPERIMENTAL METAPHYSICS: THE SCANPATH AS AN EPISTEMOLOGICAL MECHANISM Lawrence W. Stark and Yun S. Choi Neurology and Telerobotics Units, School of Optometry, University of California, Berkeley 94720-2020 Abstract Experimental metaphysics involves two experimental approaches, one to the philosophical fundamentals of epistemology, the theory of knowledge, and the other to ontology, the theory of reality. Our contribution to epistemology centers on the scanpath theory of vision: that internal cognitive models control active looking eye movements, perception, and active vision in a top-down fashion. Quantitative evidence about experimentally recorded scanpaths has recently been obtained in the form of string editing distances which measure the similarities and differences between scanpaths made by different human observers as they view a variety of pictures. A decisive new experiment documented that scanpaths during visual imagery tasks and those scanpaths formed while looking at actual pictures were the same. The subject's tasks during the imagery period was to imagine the previously viewed picture. Our contribution to ontology stems from the new field, popularly known as "virtual reality". This "hype" name describes virtual environments formed by computer generated dynamic pictures projected on video screens and worn as head-mounted displays. Interaction, immersion, and interest provide routes to a sense of "telepresence," the compelling feeling that the human subject is acting and behaving in this distant artificial environment. This raises the ontological question, "Why does one feel present in the pupil of one's own dominant eye, here and now, in the so-called 'native reality'?" The answer is that normal vision, like virtual reality, is formed by illusions — of completeness and clarity, of space constancy, of continuity in time, of instantaneous action, of vivacity — and these illusions create our sense of presence. Key Words: eye movements, scanpath, perception, string editing metrics, virtual reality, illusions, telepresence, robotic image processing