James H Elder1, Jonathan Victor2, Steven W Zucker3. 1. Department of Electrical Engineering & Computer Science, Department of Psychology, Centre for Vision Research, York University, 4700 Keele Street Toronto, Ontario M3J 1P3, Canada. Electronic address: jelder@yorku.ca. 2. Feil Family Brain and Mind Research Institute, Weill Cornell Medical College, 1300 York Avenue, New York, NY 10065, USA. Electronic address: jdvicto@med.cornell.edu. 3. Depts. of Computer Science and Biomedical Engineering, Yale University, 51 Prospect St., New Haven, CT 06520-8285, USA. Electronic address: steven.zucker@yale.edu.