Figure-ground Perception

The term figure-ground perception is used to describe the tendency of the visual system to simplify a scene into the main object that we are looking at (the figure) and everything else that forms the background (or ground). 

In the above examples, it is difficult to discern what the object is and what the background is. In the examples there are multiple interpretations of what the object is and what the background is. For example, the first picture can look like two faces close to one another, or it can also look like a vase with a black background.