GAZE MOTOR ASYMMETRIES IN THE PERCEPTION OF FACES DURING A MEMORY TASK

In 33 male and female adult volunteers, eye position recordings were p erformed by means of an infrared reflection technique. Slides of rando mly shuffled black-and-white photographs (7.5 x 10-degrees) of faces a nd vases were projected for 6 or 20 sec respectively in a visual memor y task. In each series, 10 slides of art nouveau vases and of the ''in ner part'' of masked Caucasian faces were used. During recording the h ead was fixed by a bite-board. (a) For faces the preferred targets of the centre of gaze were the eyes, the mouth and nose region, for vases the contours and some prominent ornaments. (b) Left-right asymmetries in the gaze-movement sampling strategy appeared with faces, but not w ith vases. In faces, the overall time that the centre of gaze remained in the left half of the field of gaze was significantly longer than i n the right half. (c) When, however, the amplitude of the gaze excursi ons into the left and right halves of the inspected items was taken as a measure and normalized, a preference for the right gaze field was o bserved. (d) The relative left-right bias during face inspection was s tronger with the 6 sec than with the 20 sec inspection period and sign ificantly stronger in female than in male subjects for the 6 sec tasks . (e) Left/right inversion of the face stimuli did not abolish the sid e bias. Thus the asymmetric sampling strategy when faces were inspecte d as compared to vases was due to ''internal'' factors on the part of the subjects. It is hypothesized that a left-right asymmetry in hemisp heric visual data processing for face stimuli was the cause of a left- right asymmetry in gaze motor strategies when faces were inspected.