strong enough to tell its face is actually hollow. Keen observers will note that the head doesn't actually follow them, but appears to turn twice as fast around its center than they do themselves. The Hollow-Face illusion is weaker among people with schizophrenia and other populations with psychotic symptoms, perhaps as a result of reduced tendency to interpret any kind of ambiguous 3D object as convex. It appears to be related to current mental state, namely in regard to current positive symptoms, inappropriate affect, and need for structure. The illusion seems to strengthen among successfully treated patients. People on the autism spectrum have been shown to be less susceptible to visual illusions, including the hollow-face illuson. Examples See also Illusion References External links "The Hollow Face Illusion" at Grand Illusions Optical illusions