Perception of gaze direction using 3D virtual reality displays. Effect of Sclera and Head Orientation.

Abstract

Perceived gaze direction results from a mechanism that takes into account the orientation of the eyes and the head relative to the observer (Todorovic 2006). Studies using two-dimensional images have shown that head orientation influence perceived gaze direction (Wollaston illusion; see Langton 2000). However, this effect has not been studied using 3D images; it is possible that 3D cues modulate interactions between head and gaze direction. We clarify this issue by using 3D virtual reality displays of digitized faces while manipulating eye and head orientation. We also studied the effect of the white sclera on perceived gaze direction by replacing human eyes by macaque monkey eyes. We used an Oculus rift for stimulus presentation. The stimulus presentation and data collection were conducted using Unreal Engine 4. Within a virtual world, emotionally neutral human heads with human or monkey eyes with 3 head and 7 eye orientations were presented. Subjects (n=9) judged whether gaze pointed right or left relative to them. A Weibull function was fit to the data; α (point of equality) and β (slope) were determined for each subject. We found a head orientation bias corresponding to a repulsive effect only when using human-eyes (rightward head rotation; α_Median 2.89° vs 0.05°; signed-rank test; p = 0.0039; leftward head rotation; α_Median -2.74° vs 0.05°; signed-rank test; p = 0.0195). We also found that the slope of the psychometric curves was steeper using human-eyes (human-eyes vs monkey-eyes, β_median 12.14 vs 3.87; signed-rank test; p = 0.0053). Subjects showed longer reaction times with monkey eyes (median difference= 61ms; Kruskal-Wallis p< 0.001). Our results showed that the Wollaston illusion is present in 3D displays, however, it vanishes when the white sclera is not present. This indicates that the white sclera in human eyes substantially contribute to improve the accuracy of gaze direction discrimination.

Meeting abstract presented at VSS 2018