The Gestalt laws numerous processes to identify visual recognition (perception) failed resulting optical illusions resulting.
The most common are “Fund-Figure” in which the outline of objects defines what can be found in the first or last plane.
The “Familiarity of objects” also heavily involved in the recognition and constantly compared with the known elements looking for repeating patterns.
From the point of view of the recognition of the human figures we usually identify two main patterns, the front view and profile. Any intermediate position we can interpret as a transition between the two, being the contour (profile or silhouette) one aspect that mark recognition in this case.
The picture accompanying, Received by email, is a photograph of a person front view has been partially erased by setting a contour similar to that of a person in profile. If we look a little cost us identify the position, since our recognition mechanism will be influenced by the mentioned aspects.
Do you think that figure is rotated onto her profile?