Freud distinguished primary repression (neurologically based avoidance of pain) and psychologically defensive secondary repression (repression proper), the avoidance of instinctual conflict in the whole object Oedipal period.
In the intermediate stages of development, repression is represented by the concepts of splitting and dissociation and autistic states. Working backward from the Oedipal stage, the post self-object theorists find narcissistic dissociation, splitting of self representations, and expressions of the broken primary link and the failed or dead mother.
Dissociative Identity Disorder doesn't fall neatly into this scheme, and we are left wondering if there is really any difference between a dissociation and a split, or for that matter, a repression.
But what we are really interested in is what is being repressed, split, projected, introjected and dissociated and in whom is doing it. Splits of object representations are called projections and introjections of self representations are called splits.
Dividing by the lowest common metaphorical demoninator, we are left with projection/introjection (flow of energy/meaning) between the poles of self and other, and an ego or psyche which can only repress, split and dissociate.
Summarizing, four distinctly different processes have been postulated in the history of psychoanalysis to account for the various conditions of memory. In developmental order they are:
(1) primary (neurologically conditioned) repression which acts to foreclose the possibility of reengaging in activities formerly experienced as physically painful;
(2) ego-affect splitting in which mutually contradictory affect states give rise to contrasting and contradictory self and other transference and resistance memories;
(3) dissociation in which certain whole sectors of internal psychic experience are (defensively) walled off from the main personality because they cannot be integrated into the overall span of the main personality; and
(4) secondary (policy decision) repression brought about by self instruction against socially undesirable, internal, instinctually-driven thought and activity.
The layman's notion (which judges, jurors, and survivor's groups are most likely to hold) which presupposes massive forgetting of an intense social impingement and the later possibility of perfect video camera recall, is not a part of any existing psychoanalytic theory of memory. A century of psychoanalytic observation has shown that the common sense notion of forgetting, derived as it is from the everyday experience of lapses in memory with sudden flashes of recall, simply does not hold up when emotionally charged interpersonal experiences from early childhood are involved. What appears to the layman as forgetting is considered by psychoanalytic theory to be the result of the operation of selective forms of recall which are dependent upon the nature of the relationship context in which the memories are being recalled.
Nor do psychoanalytic theories regarding how emotionally charged memories operate support the common prejudice that human beings are accurate recorders of the historical facts out of which their personal psychic existences are forged! Human memory is simply not an objective camcorder affair, but rather a calling forth or creation of subjective narrational representations within a specified and highly influential relational context.
Lawrence E. Hedges: Taking Recovered Memories Seriously