It may be stating the obvious to mention that when looking at something, we impose top-down concepts and images from our memory along with the bottom-up perception of what is in front of our eyes.
As Siân Ede says in 'Art And Science' (2005); 'When we look at a ... scene ... we may receive only partial information but our brains automatically fill in the gaps to make sense of things.'
Likewise when we stand in front of a piece of art. This tendency of our brains to 'fill in' can be exploited in art. Neurobiologist Semir Zeki believes that the most compelling artworks are those which contain only vague clues and perhaps even those works that are actually incomplete. They are the ones that make the viewer work hardest, with a pleasurable payoff when the imagination 'solves' the problem.
Although this is only a news item, it explores the work of Zeki and the pleasure some kinds of art gives us compared with other types.
Here is Semir Zeki's excellent and thought-provoking blog.