Strange-face-in-the-mirror illusion

摘要

I describe a visual illusion which occurs when an observer sees his/her image reflected in a mirror in a dimly lit room. This illusion can be easily experienced and replicated as the details of the setting (in particular the room illumination) are not critical. These observations were made in a quiet room dimly lit by a 25 W incandescent light. The lamp was placed on the floor behind the observer so that it was not visible either directly or in the mirror. A relatively large mirror (0.5 m x 0.5 m) was placed about 0.4 m in front of the observer. Luminance of the reflected face image within the mirror was about 0.2 cd m~(-2) and this level allowed detailed perception of fine face traits but attenuated colour perception. The illusion occurred even at higher levels of illumination of observer's face (from 0.2 to 1.6 cd m ~(-2)). The task of the observer was to gaze at his/her reflected face within the mirror. Usually, after less than a minute, the observer began to perceive the strange-face illusion.