OK, so some memories may be fictional but have a use in later life. What exactly is that meant to show? That the narrative that identifies me, my doings and life is meaningless because it may be based on fictionalised memories? Surely not, unless you hold that all memories have to be truth like. We all know that even interpretation of present events is based on selection and omission and dependent on interest and context.
So is the identification of who and what we are, the narration of what we see ourselves to be or want to be is not based on a truth like reading of reality, whatever that is.
No, narration of one’s life history, involves an interpretation of the past relative to the present, because the present is and must always be, the frame of reference, in terms of which any meaningful interpretation can be made. Without that frame the past has little significance.
Only very simple factual statements are open to the kind of empirical investigation that you mention and if people want to think of their past in non-truth like ways, although they think that they are, then let them read their past in romantic, optimistic or depressive ways. In contrast to the testable factual statements, narration and interpretation usually involve a set of sophisticated and interlocking theories which may be hard enough to determine let alone test.
One of the reasons for keeping full diaries over one’s life course, is that the entries not only include a record of events but more importantly the interpretation of them
Where a one seeks a unified story of one’s life course, one’s context, environment and ever evolving or changed world view are the most significant determinants of the story
As a child I was terrified of the dark, I think that this is true, my sister confirms the existence of the fear, but just how significant that fear was to my view of life then, I have no idea. Probably not as traumatic as I do now. But since then, having studied psychology and Freud in particular, I have become aware of the functions of a traumatic memory in one’s perception of one’s past.