The Noh mask effect: vertical viewpoint dependence of facial expression perception

Full-face masks, worn by skilled actors in the Noh tradition, can induce a variety of perceived expressions with changes in I-lead orientation. Out-of -plane rotation of the head changes the two-dimensional image characteristi cs of the face which viewers may misinterpret as non-rigid changes due to m uscle action. Three experiments with Japanese and British viewers explored this effect. Experiment 1 confirmed a systematic relationship, between vert ical angle of view of a Noh mask and judged affect. A forward tilted mask w as more often judged hal,py, and one backward tilted more often judged sad. This effect was moderated by culture. Japanese viewers ascribed happiness to the mask at greater degrees of backward tilt with a reversal towards sad ness at extreme forward angles. Cropping the facial image of chin and upper head contour reduced the forward-tilt reversal. Finally the relationship b etween head tilt and affect was replicated with a laser-scanned human face image, but with no cultural effect. Vertical orientation of the head change s the apparent disposition of facial features and viewers respond systemati cally to these changes. Culture moderates this effect, and we discuss how p erceptual strategies for ascribing expression to familiar and unfamiliar im ages may account for the differences.