It is a great question. I am not qualified to add any weight to the matter, but I have seen the phase shift that occurs when you speak to a JW, and they stop properly thinking and start reciting information.
Strangely, my Bible Study Conductor spoke to me about how sometimes when witnessing someone would ask a question, and he would recall an answer that he had forgotten he knew, and how it must have been the Holy Spirit taking him over. I don't think it is anything so sinister, but rather just subconsciously recalling part of your indoctrination.