Eye-movement changes associated with a height-induced threat


Height-related threat effects on the sensori-motor control of posture has been broadly studied; however, the effect on eye-movements during stance are less known. Kugler et al. (2014) showed that subjects susceptible to fear of heights have a more restricted gaze behavior when standing on heights compared to controls. Thus, we hypothesized that individuals will demonstrate less exploratory gaze behaviour when standing on high compared to low heights. Subjects (n=4, 1 female) were asked to stand facing towards a blank canvas for 5 minutes at 0.80 m above ground (away from the edge; Low) and 3.2 m above ground (at the edge; High) on a hydraulic lift (order counter-balanced across subjects). Eye movements were measured with the Dikablis eye tracker, and 6 QR code markers were used to define a fixed area for analysis (10.9 m2). Calibration trials (1 min) were performed after each condition to correct for offsets (along the horizontal and vertical axes) and normalize the subject's eye-level. The average standard deviation of gaze patterns along the horizontal direction was comparable; 36.9 cm in Low versus 31.3 cm in High. In contrast, the average standard deviation along the vertical direction was much smaller at Low (56.9 cm) versus High (122.5 cm). Contrary to past findings that subjects fearful of height freeze their gaze to the horizon (Kugler et al. 2014), these results indicate that individuals employ a more exploratory eye-movement pattern when standing on high heights.

Acknowledgments: Acknowledgement: Funded by NSERC