Proximity (Bechtel)

Proximity is when we group objects that are near to each other together. Instead of viewing a large array of figures as one group, we often separate them into several groups based on how close they are to other figures. It is how we naturally associate objects. 

This is an image of soldiers marching. We view them as rows of people instead of a group because of the way they are standing.

http://photos.cleveland.com/plain-dealer/2009/05/eye_on_the_world_tuesday_may_5_6.html