Janet Hsiao, UCSD

How is it that we recognize a face we have seen before? This process is so automatic that we rarely think about how we do it. It is often thought that we can recognize a face in a single glance. Now, a new study has shown that in fact, two glances, i.e., two fixations, are best. Cognitive Scientists Janet Hui-wen Hsiao and Garrison Cottrell from the Temporal Dynamics of Learning Center at the University of California, San Diego examined this by showing volunteers frontal-view images of faces, one at a time, and recording their eye movements with an eye tracker. By using the eye tracker, the researchers were able to measure fixation points when the faces were shown (i.e. where on the face the volunteers looked). In addition, the researchers limited the number of fixations that volunteers could make when looking at the faces to one, two, three or an unlimited number, by replacing the face with an average of all of the faces in the study when the number of fixations exceeded the limit. This is done while the eyes are "in flight" to the next fixation - when we are virtually blind until we land at the next spot.

The results, reported in the October 2008 issue of Psychological Science, showed that during face recognition, the first two places we look at are around the nose, with the first fixation point being slightly to the left of the nose. This was surprising, as previous research has suggested that the eyes may be the critical point for face perception. In this study, it was not until the third fixation that participants looked at the eyes. This difference from previous studies can be explained by the fact that in most previous studies, the face is presented in the center of gaze – subjects don’t have to move their eyes to the center of the face, because they start there.
The researchers also found that two fixations are optimal for face recognition. Given the same amount of time to view each face, the volunteers performed better when they were allowed to make a second fixation than when they could look at only one fixation. The authors conclude that the nose "may be the 'center of the information', where the information is balanced in all directions, or the optimal viewing position for face recognition.”