As an independent researcher of MBTI, it was revealed to me that many times typical traits of one type may be completely opposite when under stress, and in some ways mirroring other types under normal conditions. read more
As for nature vs. nurture, I don’t think there’s a clear cut line between where personality type is the result of nature and where it’s the result of nurture, but from my observations and readings it seems most likely that it’s a combination of the two. read more