Closure

With the law of closure, we often fill in gaps in a picture to create a complete, whole object. We ignore gaps and fill in contour lines with our minds in order to see objects.

               http://graphicdesign.spokanefalls.edu/tutorials/process/gestaltprinciples/gestaltprinc.htm

We apply this to many things in real life including in this panda, which serves as the logo for WWF. This picture of a panda has many open lines, but we fill them in with our brains and are still able to perceive the panda.