Seriously, though, most 'tests' on personality and brain activity evaluate the 'normal' or 'average' behaviour. For example, in a management course I did a long time ago, we were told about one method of assessing personalities that used two axis -- introverted->extroverted and task-oriented->people-oriented. The key thing the instructor told us was to look at your behaviour in a stress environment, not in a relaxed environment. When I'm relaxed, I can be extroverted (like I was at that course), but in a stress environment, I'm very introverted. The other students at that course were very surprised when I insisted I'm introverted....
In this case, that fact that I generally see CW movement means I'm using one part of my brain more than the other. For those who can see both easily probably have a more balanced use of their brain. I can, with a lot of effort, NOW make myself see CCW movement, but it's not something that comes easily for me -- I'm not used to using that part of my brain in this context.