Similarity of size

This picture displays a fine grasp upon the understanding of the gestalt theory. Gestalt argues that objects that look the same are "automatically" grouped together by the brain (just like RAM in computers). More precisely, this picture shows the law of similarity of size. One could notice six cans that have the same shape and color; on the other hand, one of the six cans have a different size. A person is usually interested in this picture for its dissimilarity rather than similarity. It is dissimilarity that attracts and drags attention.