This is an interesting subject, and I think one of the shortcomings of Hassan's book, RTB, is that it gives a very basic explanation of this phenomenon.
First of all, I think it is something we can all relate to. As a previous poster mentioned, we all have different personas. We have our "work persona", our "out with the guys" persona, our "religious persona". We probably all can relate to the uncomfortable feeling we get when these worlds collide. For instance I can recall drinking and having a good time at my brother's wedding. I was in my "out with the guys" persona. Then my grandmother tapped me on the shoulder. She didn't say anything, or act in any way dissaprovingly. Nevetheless, I was suddenly ashamed.
I think many of our personalites are exclusive and even contradictory.
The reason it is important to understand the phenomenon if you are wanting to help someone be open to the flaws in the jw paradigm, is that they are most open when they are not in their jw persona. THink of it as a sheild. When they are in jw-mode, their sheild is up. When they are not, it is down.
I think Jgnat brought up an excellent point, that anyone hoping to open a jw's eyes, will need to become accomplished and aware of how to manipulate a jw in and out of this mode.
Another thought I had about this is that there is some inertia involved. I think the longer a person spends in one persona, the more difficult it is to switch back to the other. Furthermore, when a person spends more time in a persona that is in conflict with another, the difficulty in switching is more profound.
The trick I think with a jw is to get them out of jw mode, but do it in a way that when the subject comes back around to something that contradicts the jw paradigm, it doesn't trigger their jw personality. This is a highly skilled bit of jiu-jitsu or maybe ballet, that I am not sure I have a good idea how to employ. Furthermore, it requires a level of sophistication that is difficult to realistically inject into a spontaneous conversation. To attempt to force it into a conversation is to risk coming off like a salesman. This subject is definitely an area where I lack a solid understanding.
CYP