After thinking about the past and imagining the future, how do people separate these real and imagined events in memory? We had subjects engage in past and future autobiographical elaboration, then later take memory tests that required them to recollect these earlier generated events. In Experiment 1, testing memory for previously generated past or future autobiographical events led to fewer source memory confusions than did an elaborative control task, suggesting that the distinctive features of autobiographical elaboration improved subsequent retrieval monitoring accuracy. In Experiment 2, we directly compared retrieval monitoring accuracy for previously generated past and future autobiographical events and found that subjects made fewer source confusions when searching memory for future events. This asymmetry suggests that the features characterizing future elaborations (e.g., cognitive operations) were used more effectively during reality monitoring than were the features characterizing past elaborations (e.g., perceptual details), and has implications for future-oriented theories of memory.
Memory confusion can occur between events that actually happened and events that were only imagined. For instance, people can confuse whether they performed some action or imagined it (e.g., Goff & Roediger, 1998) or whether some autobiographical event was real or only imagined (e.g., Garry, Manning, Loftus, & Sherman, 1996). Such confusions between an event originating from an external source (perception) and an event originating from an internal source (imagination) are called reality monitoring errors (see Johnson & Raye, 1981, for a review). Reality monitoring fits into a general source monitoring framework (Johnson, Hashtroudi, & Lindsay, 1993), asserting that people recollect features of information and must use these features of information to reconstruct memories. Because this reconstruction process is not perfect, we must infer missing features of information through retrieval monitoring processes.
To apply reality monitoring research to autobiographical memories, it is important to know what types of imagination are common or important in daily life and thereby most likely to be confused with real events. According to the constructive episodic simulation hypothesis, a critical function of autobiographical memory is to imagine possible future events and plans (Addis, Wong, & Schacter, 2007; Schacter & Addis, 2007; Schacter, Addis, & Buckner, 2007). In fact, it has been argued that the ability to remember evolved from the need to generate plans and actions for the future (e.g., Suddendorf & Busby, 2005; Suddendorf & Corballis, 1997, 2007) and that the ability to generate future simulations may have been given adaptive priority (Schacter et al., 2007). Consistent with the idea that past and future autobiographical elaboration have overlapping cognitive processes, recent studies have shown that the neural signatures of remembering the past (past elaboration) are similar to those of imagining the future (future elaboration) (e.g., Addis et al., 2007; Szpunar, Watson, & McDermott, 2007), suggesting overlapping processes between past and future events. Moreover, like past elaboration, future elaboration entails the creation of a scene that has a narrative structure accompanied by a sense of mental time travel (Tulving, 1985) and is likely to involve self-referential processing when considering one's future goals or plans (Conway, 2005). This research highlights the similarities between past and future events, in that both involve reconstructive processes that operate on similar features or episodic content (Botzung, Denkova, & Manning, 2008; Buckner & Carroll, 2007; Schacter et al., 2007; Szpunar et al., 2007).
If imagination of future autobiographical events is a critical function of human memory, the high degree of overlap between past memories and future imaginations that has recently been uncovered by neuroimaging and subjective reports poses a major theoretical question for reality monitoring processes. …