We can quickly spot a face staring at us in a crowd. We can do this much quicker, for example, than we can determine that no one is staring at us, as this movie demonstrates. A grid of 100 pictures of Greta will be flashed for about 1/3 of a second. Can you spot the photos where she’s looking at you? You’ll see two different grids.
Most people are able to detect the staring faces much faster than those looking to the side. But we can also sometimes be fooled by faces, something we discussed on one of the first-ever CogDaily posts:
In this picture, the eyes for each face are exactly the same, but the face on the right appears to be staring directly at us, while the face on the left seems to be looking off to the viewer’s right.
A similar effect can be achieved in reverse, keeping the head position the same while changing the eyes:
Faces 1 and 2 are identical except for the eyes, and face 1 appears to be looking at us while face 2 seems to be looking away. Meanwhile, neither face 3 nor face 4, which use the same eyes as faces 1 and 2, seems to be looking at us. So when the only difference between the faces in a group is a subtle difference in eye position, will we still spot the pictures that seem to be looking at us faster?
Hirokazu Doi and Kazuhiro Ueda showed volunteers these faces arranged in groups of nine:
In every case, eight of the faces were the same. Half the time, the ninth face was subtly different (only the eye orientation was different), and half the time it was the same as the other eight. Viewers pressed a key as quickly as possible to indicate whether all the faces were the same or there was one different face. Here are the results:
This graph shows the average reaction time when one of the faces was different from the others. When the different face appeared to be looking right at the viewers, they reacted significantly faster than when it was looking slightly to the side.
This occurred even in the case of pictures 1 and 2, where the head orientation was identical.
A similar pattern was found when all the faces were the same: people took longer to decide that the faces were the same when it was looking straight at them, compared to faces looking away, even when the head orientation is the same.
Doi and Ueda say that in one sense this is unsurprising because staring faces attract our attention faster than faces looking away. But what’s surprising is that we appear to process the whole face (is it looking at us or not?) faster than we process the local features about that face (the orientation of the head and eyes).
Hirokazu Doi, Kazuhiro Ueda (2007). Searching for a perceived stare in the crowd Perception, 36 (5), 773-780 DOI: 10.1068/p5614