Figure-ground perception

When your brain sees a figure in the background. In this photo you can see the faces created with the space between the figure and the ground. 

Proximity

When we group nearby figures. These pencils are seen as three groups of two not just six pencils.

Similarity

When we group together figures that are similar to each other. We see these bottles and cans separately going straight down not across.

Continuity

When we perceive smooth, continuous patterns rather than discontinuous ones. We perceive these lines to be one curved line and one straight line not one line as a whole.

Closure

Closure is when we fill gaps to create a complete, whole object. In this photo the circles are half but we can perceive them as whole