If they don’t remember it, how do they know it happened?
I had dreams as a very young child that are like real memories to me now - but I know they were dreams.
One of thing the UFOs teach us (if we are willing to learn) is that our hard and fast categories of reality, dreams, memory, death etc. are oversimplifications of the way the world works.
Humans have some base assumptions which are drilled into them by our current culture—so basic we often don’t even realize they are there.
When you start digging deeply into the UFO world you start to run into these things—and start to ask a lot of questions—”How do I know this is true?” “Is there any way it could be wrong?”
Many people who come to them with fuzzy thoughts about how they might have been abducted start to recall over time all that has happened to them. It is traumatic.
Though they can't establish in every case that parents and grandparents were also abducted (because some parents et al are dead at the time), they have been able to put together patterns that demonstrate that it is profoundly generational.
They did use hypnosis (mostly to relax their patients to improve recall) but they learned to establish careful protocols so as to not influence any recall.
Though Mack and Hopkins are now dead and Jacobs is retired, for the most part, their work has been recorded in many videos, papers, and books. MIT hosted (not sponsored, hosted) a symposium on UFOs and the abduction experience where scientists and researchers presented over 118 papers on the subject. Here are some links (they are well worth examination...and there are many other sources than the ones listed below):
Alien Discussions: Proceedings of the Abduction Study Conference Held at M.I.T. Cambridge, Ma. Textbook Binding – January 1, 1995You don't need to buy the books to read the reviews and comments. I have read them all--the books that is--and they are quite good if scary as hell.Close Encounters of the Fourth Kind Hardcover – January 1, 1995 by C D B Bryan
Final Note: No one knows what the hell we are dealing with here but it isn't insanity. It is hard to draw any absolute conclusions.
Not mentioned above are the accounts of Dr. John Mack of Harvard. His accounts are actually the best. As an aside, Mack's tenure as a professor of psychiatry was challenged by the Harvard Medical School, the faculty of which he was a tenured member. They tore his work and career apart looking for anything they could use to recall his tenure. They failed. They could only conclude that he performed his work in a professional even laudable manner.