The Noh Mask Effect: Culture and View Dependent Facial Expression Perception

Out-of-plane rigid rotation of the head distorts metric properties of the face as it appears in the two dimensional projection of the visual world on the retina (Cavanagh et al., 1988, Kappas et al. 1994). It is interesting to ask whether this distortion interferes with the interpretation by visual system of the non-rigid displacement of internal facial features due to facial expression. In other words, is facial expression perception viewpoint invariant? The present study was stimulated when we learned that certain masks (figure 1) used in Japanese Noh drama appear to change expression as the vertical inclination of the mask is changed. Tilt the mask forward and it appears to smile; tilt it backwards and it appears sad.