Eye-movement changes associated with a height-induced threat

Authors: Hollman R, LuuMJ, de Faye S, Carpenter MG

Affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC

Height-related threat effectson 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 heightshave a more restricted gaze behavior when standing on heights compared to controls. Thus, we hypothesizedthat 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 towardsa blank canvas for 5 minutes at 0.80 mabove ground (away from the edge; Low) and 3.2 mabove ground (at the edge; High) on a hydrauliclift(order counter-balanced across subjects). Eye movements were measured with the Dikabliseye tracker,and 6 QR code markers were used to define afixed 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 alongthe horizontal direction was comparable; 36.9 cm in Lowversus 31.3 cm in High. In contrast, the average standard deviation alongthe vertical direction wasmuch smaller atLow(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 patternwhen standing on high heights.

Acknowledgement: Funded by NSERC