Ambiguous figure illusions: do they offer a window on the mind?

Do you see a wife, or a mother-in-law in this picture? Ambiguous figures have intrigued scientists since the 1800s, but what can they tell us about our visual system? This figure is called ‘My Wife and my Mother-in-Law’. There are two different ways of interpreting this image. One is of a young lady looking back over her shoulder, the other of an elderly lady in profile looking down. This sort of image is referred to as an “illusory” or “ambiguous” figure. In