We investigated the effect of familiarity on people's perception of facial
likeness by asking participants to choose which of two mirror-symmetric chimeric
images (made from the left or right half of a photograph of a face) looked more
like an original image. In separate trials the participants made this judgment
for their own face and for the face of a close friend; half of them matched to a
true image of the original and half matched to a mirror image of the original.
In the case of matching to a friend's face presented in the familiar
orientation, over 80% of participants chose the left-left composite to be a
better likeness to the original, whereas only 62% showed the same left-side bias
when matching to a mirror image. The difference is significant, and the result
contrasts markedly with a second experiment where participants who were
unfamiliar with the faces showed comparable left-side biases when matching to
true or mirror reversed images. The result suggests that perceptual asymmetries
are retained in our long-term memory for highly familiar faces. While matching
to images of self also showed an effect of familiarity, the data in this
condition show less evidence of perceptual asymmetry and are discussed in
relation to recent research on the representation of one's own face