Eye and Head Coordination During Reading

Abstract

Abstract: : Purpose:The maintenance of stable gaze, the sum of eye position relative to head and head position relative to space, is essential for the normal reading task. However, the mechanisms by which the brain achieves the fine, tightly controlled coupling between eye and head movements are unclear. Previous literature relating to strategies of head and eye coordination used during reading is limited to one publication in which readers followed Korean text covering 90° of the visual field (Lee, 1999). We have investigated head and eye strategies during reading of English text in which a normal reading task (A4 size, 28.6° width) was compared to that covering 90° of the visual field. Methods:Head and eye movements were monitored using an infrared pupil and head tracker. In addition, a mechanically independent measure of transient changes in head movements was recorded using a tri-axial accelerometer. The subjects were instructed to read an A4 card (A4 text) filled with single spaced, 12pt text of Times New Roman font. A second card of dimensions 550mm wide and 100mm high (wide text) contained different text but with the same style as used in card 1. The process was repeated with the exception that the content of the text was switched between the two 90° and A4 cards. Results:As previously noted, subjects made a consistent slow movement of the head during the reading of 90° text accounting for approximately 40% of the gaze amplitude. The velocity of the head movement significantly increased over the course of the first trial and remained higher for the second trial. During the normal reading task (A4 text) the head movements only accounted for approximately 5% of gaze amplitude. Head movement velocity also significantly increased over the course of the two trials. The A4 reading task was associated with a significant slow vertical head movements, which significantly increased with time. A small modulation of head movement velocity was evident during eye saccades regardless of the task used. Conclusion:Head movements during normal A4 reading were highly consistent with little horizontal movements but significant vertical movements. During normal reading and the 90° reading task, head movements show adaptation both within tasks and between tasks. Our results suggest that head and eye movement systems are highly coupled but extremely flexible. A smaller modulation in head movements compared to previous studies may be due to differences in word structure of the languages used.

Keywords: 406 eye movements • 539 reading • 495 ocular motor control