Abstract
Head rotation is a cue for perceived gaze direction in face perception. This work examined how perceived head orientation is influenced by the dynamic rotation of neighboring faces. Within each trial, two identical contextual faces were presented 3.2° to the left and right of fixation for 240ms. Halfway through the presentation of contextual faces, a static target face appeared briefly (27ms) at fixation. Observers reported whether the target face was rotated further to the left or right than the contextual faces. Target face orientation was varied from trial to trial, so that the point of subjective equality (PSE) for head orientation between target and contextual faces could be measured. Three conditions were interleaved: contextual faces were either dynamic (rotating from 4 to 16° or 16 to 4°) or static at a head rotation of 10°. All three conditions were similar during target presentation, in that dynamic contextual faces were oriented at 10° during the 27ms target exposure. The PSE (n=4) for the static condition was 9.9° (±1.1°) but for rotating conditions shifted to 15.1° (±2.0°) and to 3.0° (±1.0°) for the 4–16° and 16-4° directions, respectively. Results suggest that perceived head orientation is influenced by that of neighboring faces, and that when contextual faces undergo a dynamic rotation, the flashed face appears to lag behind. This demonstrates that the flash-lag effect applies to complex constructs and motions, such as head rotation. Implications for motion mechanisms and perceived gaze direction are addressed.
This work was supported by an NIH grant to HRW (# EY002158), by a CIHR training grant in Vision Health Research, and by a CIHR Postdoctoral Fellowship to CH.