|Do you see faces or a vase?|
In the book, readers learn that the left hemisphere (the dominant one in most people) is in charge of speech, logic, and most intellectual pursuits like analyzing, using symbols, and thinking abstractly. It also keeps track of time and presents things in a linear, sequential fashion. The right-brain is in charge of nonverbal communication, intuition, spacial relationships between objects, object recognition, nonlinear thinking (thinking 'outside the box'), and holistic perspectives (seeing the 'big picture' and the patterns in it).
This reminded me very much of the plotters versus pantsers in writing. Those who don't prefer to outline might simply be more right-brained when they work. Meanwhile, the left-brain is concerned with sequence, and order.
Because your right-brain controls your left side and your left-brain controls your right side, ambidextrous and left-handed people have more crossover between the hemispheres of their brain. Their hemispheres 'share' more and they might display more right-brained traits in their everyday life. It doesn't mean they're artists or musicians, but they have a tendency toward great ideas, spacial relationships and 'thinking outside the box'.
I'm right-handed, but I learned recently that I use my left side/right-brain more than a lot of other right-handed people. My right-brain (left hand) dominates in ways I hadn't realized before. I'm also good at seeing spacial relationships between objects, good at non-linear thinking (I'm a pantser), intuitive, and good at picking up the nonverbal queues people give off. I think I inherited this, since my mother has a lot of these same traits.
The point of the vase/faces image is that you draw one side and then you try to draw the other side to compliment it. This exercise is designed to allow the 'shift' between left-brain and right-brain thinking. It's only one of the great exercises in Drawing On the Right Side of the Brain.
What about you? Are you in your Right Mind?