Source: http://en.wikipedia.org/wiki/Gestalt_psychology
All other information unknown

The Gestalt Principle of Reification is the idea that the image your viewing contains more spatial information than what it provides in positive space. This is a basic example of reification, its a simple concept, so it’s not normally used so plainly in artwork. Basically, reification is the idea that there is information in the negative space that is created through the use of the positive space; as shown above, the separate shapes put together in a particular way create another shape in the negative space.