Apparently, MBTI practitioners are taught that preference scores indicate clarity within the user, not strength of preference. So, 100% N doesn't mean you're a total N-head, it means you are very, very clear that you prefer to use iNtuition. Likewise, say, 52% T does not mean you're close to the T/F divide, but instead that you're not consciously so sure you prefer Thinking over Feeling. And either way, being clear (or unclear) about your preferences is different from actually having preferences within your psychological makeup. So, it would seem, scores can change over time the more clear a person becomes about who they are (and, I guess, always were.).
Presumably we need from somewhere a good meaning for the term "preference". If say one prefers T over F, does "prefer" mean you can approach the world in an F way if you want but you like it better if you do T; or does it mean that trying to go against your preference is sufficiently psychically painful that you generally won't try it.
Are there really strengths of preference? Are there people who can genuinely easily switch preference? (As opposed to people who think they can easily switch.) How hardcore is "preference" really?
I have the intuition that if there are weak preferences then there are weak personalities--personalities without clear definition. And I say this because it seems like "personality" really only exists over time. If there isn't a consistency, there isn't a personality. Or is there?
How can we know?