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We started our eye tracking experiences with a paradigm that required subjects to do a radar tracking task for up to 3 hrs per session with each session divided into a series of 15-min scenarios. Ss could take breaks between sessions. Because of the length of the total session we worried that a head-mounted system would be too heavy and, over time, become extremely uncomfortable. Hence, we went for the magnetic head tracker. Unfortunately we never got the accuracy that we required from the MHT. For the past year we have been using a chin rest that my brother-in-law salvaged for us from some old optometry equipment. We calibrate Ss as they are in the chin rest and have them use the chin rest the entire time they are in the scenario (for each 15-min scenario). The chin rest has improved our accuracy greatly. To my surprise, none of our Ss has complained about it. We are sold on the value of chin rests. They (a) hold people's head still while calibrating; (b) relatively still during the scenario (compared to the MHT); and (c) give them a "calibrated" place to return to if they choose to move around or get up between scenarios. Chin rests may not be useful if you are doing reading research where you need to know which letter a person is looking at, but in our simulation the visual angle between screen objects is typically much greater than the visual angle between letters in a word. All in all, we believe that we are now getting data that is as accurate as we can expect. Hope this helps. -- _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ Wayne D. Gray, Professor of Psychology Program Director HUMAN FACTORS & APPLIED COGNITIVE PROGRAM SNAIL-MAIL ADDRESS (FedX et al) VOICE: +1 (703) 993-1357 George Mason University FAX: +1 (703) 993-1330 ARCH Lab/HFAC Program ************************ MSN 3f5 * Work is infinite, * Fairfax, VA 22030-4444 * time is finite, * http://hfac.gmu.edu/~gray * plan accordingly. * _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ -- EYE-MOVEMENT mailing list ([log in to unmask]) N.B. Replies are sent to the list, not the sender To unsubscribe, etc. see http://www.jiscmail.ac.uk/files/eye-movement/introduction.html Other queries to list owner at [log in to unmask]