Much of what we know of perception has come from studying illusions. Finding situations were the processes reveal themselves in their ‘mistakes’ give clues to how those processes work under ordinary conditions. Of course, our sensory processes have not actually made a mistake; we have misled them.A new illusion is a new departure because it added the specialized perception of faces to visual effects.
Giovanni Caputo from the University of Urbino has developed an experimental setup involving an observer staring for a long time at their face in the mirror under low light conditions, low enough to weaken colour perception. By a minute of fixed staring the face started to change. By 10 minutes, the subjects had seen:
(a) huge deformations of one’s own face (reported by 66% of the fifty participants); (b) a parent’s face with traits changed (18%), of whom 8% were still alive and 10% were deceased; (c) an unknown person (28%); (d) an archetypal face, such as that of an old woman, a child, or a portrait of an ancestor (28%); (e) an animal face such as that of a cat, pig, or lion (18%); (f ) fantastical and monstrous beings (48%).
You will notice that these percentages sum to more that 100% and so the images in the mirror may have gone through more that one transformation.
Under this situation of prolonged staring at a central fixation, the perception of an object is expected to get weaker or vanish. This is not what happens with faces in situations were an object should disappear, a face does not but instead is free to become another face. Here is another piece of evidence that perception of faces is very special and not like seeing other things. My way of looking at this illusion is that the object ‘face’ remains in place but the attributes bound to that face disappear in the prolonged fixed staring. Other attributes can then take the place of the original ones.
Interestingly the face in the mirror also loses its identification with the subject’s self and becomes a vision of another. Only the face remains not the look or the identity. Face appears to be a powerful category, which is probably why we see them anywhere (clouds, cracks) and why we spend so much time looking at people’s faces (not feet or shoulders).
Caputo, G. (2010). Strange-face-in-the-mirror illusion Perception, 39 (7), 1007-1008 DOI: 10.1068/p6466