Here is an article on right-left brain hemisphere tendencies as they relate to creativity.
I appreciate the article which I've linked above, because it challenges a common set of fallacies-- especially the one that assumes that only "right-brain" people can be artists. Each person, and each activity, needs both hemispheres of the brain. However, it is fascinating to begin to understand the way that each hemisphere's processing capacity can be consciously activated and realize that each of us might have a tendency to rely more heavily on one mode than the other.
Betty Edwards, who wrote Drawing on the Right Side of the Brain, is one of the names most associated with the study of the brain's hemispheres in relation to drawing. Her exercises and observations help people who feel that they cannot draw the world as it appears. By confounding the left hemisphere's forceful symbol-based logic, there are ways to get past what something "should" look like and arrive at an observational accuracy that has far more to do with curves and angles and distances than eyes and hair and teeth, for example. The result is that you can get people to look like people, and capture their particularities, with practice.
Gary Wood's drawing of Hugh Laurie
In contemporary illustration, these techniques are helpful if you are after a certain veracity. However, symbolic drawing also has a very privileged place at the table. A host of visual languages are employed and enjoyed by the contemporary audience.
Draw your attention (pun only half-intended) to the fact that black lines do not actually hold in the world around you. Line work is, instead, a human language short-hand to show where one object ends and another begins. It's all about the perception of edges. So what parts of an object are most important for determining a contour? What can be left out?