1. Posture considerations writing with head mounted eye tracker 10-12 April 2012, Mshs, University of Poitiers, France

2. Eye trackers primarily designed to read on screen have geometric requirements. Participant line of sight should be perpendicular to the screen surface (more or less). 10-12 April 2012, Mshs, University of Poitiers, France

3. Handwriting support can be “tilted”. Nowadays, handwriting is usually done on a flat surface, not a vertical one. Except in this case ! (Beware to backache) 10-12 April 2012, Mshs, University of Poitiers, France But when seated, problems with line of sight tends to appear.

4. When seated: from the eye tracker head camera (and participant) point of view, screen is not a square, but a trapeze participant moving up / down or tilting head creates parallax effect: gaze point is miscalculated. participant are closer to “screen” than recommended by manufacturer: because of forearm length, participant’s eye is about 35 cm from screen. 10-12 April 2012, Mshs, University of Poitiers, France

5. A solution Participant stands up, desk is elevated toward his elbow. electrically adjustable height 10-12 April 2012, Mshs, University of Poitiers, France