SAME BOWL OF VEGGIES... OR IS IT?
This still life by Italian painter Giuseppe Arcimboldo (left) includes the ingredients for his favorite minestrone soup and the bowl to serve it in. Turned upside down (right), Arcimboldo's bowl of vegetables becomes a whimsical portrait of a man's head, complete with bowler hat.
There are several interesting aspects to this illusion. First, why do we see a face in the arrangement, when we know that it is just a bunch of vegetables? Our brains are hardwired to detect, recognize and discern facial features and expressions using only minimal data. This ability is critical to our interactions with other people and is the reason that we perceive personality and emotion in everything from crude masks to the front end of cars.
Second, why do we see the face much more clearly when we flip the image vertically? The answer is that the same brain mechanisms that make face processing fast and effortless are optimized to process right-side-up faces, so upside-down faces are much harder to see and recognize.