This image shows the observe side of a mask that has been painted to showcase a face. When people see the reverse side of a mask, they are usually unable to perceive it as concave or a hollow face, but instead see a convex regular face as seen in this image. This illusion is a classic example of how brain uses its top-down expectations to shape visual perception. The ““Predictive coding account of perceptual inference”” suggests that brain has a model of the world and this generates an expectation of how things should look which is used to explain the visual input it receives. When the priors are very robust in this instance, faces are always convex in real life, then the incompatible visual input is reinterpret to fit this expectation, resulting in this illusion. Such illusions are not only fun but useful to study certain psychiatric conditions. Neuroscientists have found that people suffering from schizophrenia instead see the veridical percept of a hollow face instead, which suggests a pathophysiological account of how patients’ brains perceive relying less on their expectations. Could this be the reason for these patients to hear voices?
