The first two points that people look at to tell whether a face is familiar to them or not are around the nose, American researchers have revealed.
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.
They used an eye tracker to record the movements of the participants, which helped detect where on the faces shown the volunteers looked.
The researchers also 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.
It was done while the eyes were "in flight" to the next fixation, when the participants were virtually blind until they landed at the next spot.
Reporting their findings in the journal Psychological Science, the researchers said that the first two places the participants looked at were around the nose, with the first fixation point being slightly to the left of the nose.
While previous studies had suggested that the eyes might be the critical point for face perception, the latest study showed that it was not until the third fixation that participants looked at the eyes.
The researchers also found that two fixations were 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.
"This suggests that the second fixation has functional significance: to obtain more information from a different location," said the authors of the study.
They concluded that the nose "may be the 'centre of the information, where the information is balanced in all directions, or the optimal viewing position for face recognition."