Good question
I went in as an adult... 27, but I was very vulnerable.. I had recently broken off my relationship with my son's father and my own father had passed away only 2 months after that... I was under a lot of stress...
The loss of my father hit me very hard, and I began searching for answers to questions that I had no real reference to. When the witnesses knocked on the door, they seemed warm, kind and very sincere... and they seemed to have the answers to my questions... I didn't really understand the issues but hey... the answers sounded great!
What I didn't realize at the time was I was looking for a safe haven, I was in a place I had never been before emotionally and I was looking for security... and the WT provided an appearance of that.. and I was fooled by it. I don't think the problem is especially stupidity... although I do feel quite stupid for being duped ... I think it's a matter of reference and vulnerability... I beleive that if I had some kind of religious reference that helps you to identify cults... or even better, some real training in logical thought, I think it would have gone a long way to help me be less vulnerable to the WT.
Also, the way the WT presents it's material... they word it in such a way as to make it appear foolish not to agree with them.. It's sometimes subtle and sometimes blatant.. but hey, effective... who wouldn't want to live forever in perfect health having everything you ever wanted and spend eternity with loved ones... and if all you gotta do is sell magazines and books to get there.. .well, let me at them books and magazines... simple emotional appeal... not in any way logical...
It took me ten years to realize my mistake... I was such a busy little JW that I didn't have time to reflect.. not once in ten years... but, then I broke my leg in several places... (would you believe stepping off a curb on a friday the 13th... hahahahaha. how's that for luck eh, don't knock it.. I got my life back... lol ) ... and suddenly I had lots of time to reflect. Within weeks of that... I started to find out the truth about my religion and I started to see the flaws in my own reasoning.... I started to see a business where a religion once was... and I woke up... but you need time to do that... and the WT is very good at stealing your time, at indoctrination and fear tactics.. breaking my leg or being laid up somehow was the only way I was ever gonna have that time....
It's funny that JWs haven't much picked up on that ... they are all gung ho about visiting people in hospital... where most can't actually do any real research.. .but they are not so enthusiastic about visiting the infirm at home... where all the books, all the reference material.. and best of all, the computer, the WT CD and the internet are...big mistake... yep.. they left me alone, to my own devices... and I found out the real truth about the WT...it kinda makes me laugh...
I was gonna go on... but there's enough there for another post... lol
Inq from the broken but free class