Despite many similarities (see Chapter 4), some important differences can be found between involuntary and voluntary autobiographical memories. These differences are best explained as consequences of the different ways in which the two kinds of memories are retrieved. As pointed out by Tulving more than thirty years ago: “the interaction between trace information and retrieval information [is the] sine qua non of all memory phenomena” (Tulving, 1974, p. 75). In other words, the content of both involuntary and voluntary autobiographical memories is formed by an interaction between the retrieval process and stored autobiographical information. Because of the dissimilar retrieval mechanisms characterizing the two kinds of memories, the content of involuntary and voluntary recollections tends to differ on some dimensions.

The most direct evidence for this claim comes from a recent diary study examining representations of possible personal events in the future that come to mind involuntarily – that is, with no preceding retrieval attempt (Berntsen and Jacobsen, in press). Such involuntary future representations (or flash forwards) were compared to representations of future events recalled voluntarily in response to cue words.