I know that the general answer to this question can be found easily. It was added to the Book in 1981, which is when Spencer W Kimball was the president of the Church. So it could probably be said that it was written under his direction - or something like that. However, I'm interested in more information than that. Also, although he did write at least one book I can think of, at that time President Kimball was having health problems which seem to me may have stopped him from doing much more than just approving writing work.
I'm wondering if there's any specific information about who wrote the Introduction, who supervised the writing of it, or anything like that - or if it was just anonymously produced "by The Church".