Metaphorically, vision can be described as "open" or closed." A person with "open" vision can expand or open his or her perception to see "laterally," sliding off to a new track. To have a sense of humor one needs lateral vision. At the moment we understand a joke or see a new parallel to our thoughts, we are seeing and thinking laterally. This ability is a hallmark of the creative process. If the eyes and vision system are more flexible, it is easier to develop and expand one’s "creative" vision.