به یاد گذشته برای پیش بینی آینده در اواسط دوران کودکی: رشد ارتباط بین حافظه کاوشی و حافظه اپیزودیک

Prospection is the mental simulation of future events and may promote positive, future-oriented action in the present. Despite evidence of a relation between prospection and episodic memory, there is a paucity of research comparing the developmental trajectories of each during middle childhood, a time of substantial episodic memory development. This study examined prospection and episodic memory in 5-, 7-, and 9-year-old children and adults (N = 80). Participants provided narratives and introspective judgments about their experience of mentalizing past and future events. The development of prospection was more protracted than that of episodic memory, although individual differences in past event episodicity predicted prospection. Although both prospection and episodic memory were characterized by a rich subjective experience, future events were rated as more difficult to envision and were more frequently viewed in the third-person perspective. Although both prospection and episodic memory appear to improve during middle childhood, results suggest that prospection may require additional skills.

Prospection is the ability to mentally project forward in time in order to pre-experience future events (Tulving, 1985 and Tulving, 2005). This capacity is critical for adaptive behavior. While it is possible to plan for the future based on a factual understanding of contextual consequences (e.g., I will practice piano because I want to be part of the year-end recital), mentally pre-experiencing possible outcomes (e.g., pre-experiencing the feeling of joy at being selected or disappointment at being excluded) connects an individual with a future self and may provide stronger motivation for action (Suddendorf & Corballis, 2007). Although the capacity to anticipate future events is associated with a number of abilities including planning (Hudson et al., 1995 and Thompson et al., 1997) and reasoning about mental states (Lagattuta, 2007), a special role for episodic memory has been proposed (Schacter and Addis, 2007a and Schacter and Addis, 2007b). Episodic memory is the capacity to mentally reinstate a personally experienced event in specific, sensory–perceptual detail (Conway, 2001, Tulving, 1972, Tulving, 1985 and Tulving, 2005). Despite their opposite temporal directions, episodic memory and prospection are similar in that they involve mentalizing about personal events that are isolated in space and time and contain rich contextual features (Tulving, 1985). Both are also characterized by autonoetic consciousness, which enables one to be aware of (and reflect on) one's subjective experience during an event's mental simulation (Tulving, 2001). Therefore, reports on phenomenological experience (such as the clarity and visual perspective of an event) may provide important insight into the similarities and differences between mentalizing past and future events. The Constructive Episodic Simulation hypothesis provides a theoretical basis for an emphasis on similarities between these abilities (Schacter and Addis, 2007a and Schacter and Addis, 2007b) by proposing that the mental simulation of future events involves accessing and then recombining details from one's autobiographical memory (Conway, 2001) in order to mentally simulate a realistic, yet novel, future event. From this perspective, remembering the past and mentally pre-experiencing the future are integrally related. Empirical comparisons of the functioning of episodic memory and prospection suggest a strong relation between the two abilities in adults. Although representations of past events tend to be more detailed than future events, variables like valence and temporal distance affect past and future event representations similarly (D’Argembeau & Van der Linden, 2004). We also know there are commonalities in the neural substrates supporting these abilities (Addis et al., 2007 and Buckner and Carroll, 2007), and that impairments in episodic memory often co-occur with impairments in prospection (Tulving, 1985 and Williams et al., 1996). Although these similarities support a functional relation between episodic memory and prospection, an important additional question is whether these two abilities exhibit similar developmental trajectories. The present study addresses this question by investigating the relation between episodic memory and prospection during middle childhood and comparing children's abilities to those of young adults. 1.1. The development of episodic memory during middle childhood Developmental studies show robust improvements in episodic memory during middle and late childhood (Billingsley et al., 2002, Ghetti and Angelini, 2008, Ghetti et al., 2011, Piolino et al., 2007, Schneider et al., 2002 and Shing et al., 2008). In a study of personal event narratives, Piolino and colleagues (2007) asked 7–13-year-olds to report specific personal events from three different time periods in the past and to describe these events with as many details as possible. Analyses of event narratives revealed age-related increases in the episodicity of events within each time period (see also Picard et al., 2009 and Willoughby et al., 2012). Similar developmental improvements have been observed in studies (Ghetti and Angelini, 2008, Ghetti et al., 2011 and Shing et al., 2008) in which children were shown a series of items and asked to remember each item and its associated contextual features or subjective experience (defining features of episodic memory; Tulving, 1972). Results from these behavioral studies are complemented by developmental research on the neural substrates of episodic memory showing similar age-related differences (DeMaster et al., 2013, Ghetti et al., 2010 and Ofen et al., 2007). Together, these studies yield strong evidence of a protracted developmental trajectory for episodic memory. Since prospection and episodic memory are thought to be related, one might expect their developmental trajectories to mirror one another. However, the Constructive Episodic Simulation hypothesis (Schacter and Addis, 2007a and Schacter and Addis, 2007b) suggests that prospection relies on episodic memory and may therefore be a more constructive and cognitively demanding process. If true, the development of prospection may lag behind that of episodic memory, its trajectory more protracted. It is also possible that there is no evident developmental relation given that the developmental trajectories of episodic memory and prospection may be constrained by cognitive processes unique or differentially important to one over the other. 1.2. The developmental relation between episodic memory and prospection A lack of prior research makes it difficult to compare the development of prospection and episodic memory during middle and late childhood. However, research provides some support for an early developmental relation. Busby and Suddendorf (2005) asked preschoolers to report things they did and did not do yesterday, as well as things they would and would not do tomorrow. Analyses revealed significant improvement in children's ability to report both yesterday and tomorrow events between ages 3 and 5. More importantly, there was a positive correlation between 3 and 4-year-olds’ ability to bring to mind and report true yesterday events and likely-true tomorrow events, supporting a positive relation between episodic memory and prospection during early childhood. Quon and Atance (2010) have provided additional support for an early developmental relation. Preschoolers were asked content questions (e.g., “What did you do/get/eat…?”) about past, generalized present (semantic memory condition), or future events that varied according to the level of control a child would typically have during those events. Results revealed age-related improvement in the accuracy of children's reports across all three conditions (per parental ratings). Additionally, high-control events were associated with greater response accuracy than low-control events across past and future conditions only; there was no effect of control in the semantic memory condition. This result suggests that both episodic memory and prospection develop gradually across the preschool years and supports a relation between past and future thinking that may not extend to semantic memory. Together, these studies provide nascent support for a developmental relation between episodic memory and prospection. Nevertheless, there are many unknowns – two of which we address here. First, given the protracted development of episodic memory, it is important to trace the developmental trajectory of prospection beyond the preschool years. Second, episodic memories are characterized by vivid subjective experience. If episodic memory and prospection are functionally related, introspective reports should capture these mentalizing activities during prospection, as is the case for episodic recollection (Ghetti et al., 2011). Additionally, if developmental differences in the ability to introspect on episodic memory are evident, these should extend to prospection. No study to date has compared children's phenomenological experiences during episodic memory and prospection. 1.3. The present study To address the aims of the study, we adapted a cue-word technique developed for school-aged children (Bauer, Burch, Scholin, & Guler, 2007) and a recollection/prospection paradigm used with adults (Addis et al., 2007). Participants were presented with cue words and asked to generate past and future event narratives related to them. Temporal distance and direction were varied within individuals; participants provided narratives about events occurring one week and one year into their personal pasts and futures. Research has shown that temporal distance affects the contextual quality of adults’ reports of past and future events similarly (D’Argembeau & Van der Linden, 2004), but should not affect the ability to retrieve semantic information about events. Results indicating a similar effect of distance on children's past and future event narratives would therefore support a developmental relation between episodic memory and prospection. Event narratives were assessed for veracity by parent or close other to ensure that past events were true and future events were likely to be true (as opposed to implausible or make-believe). Although we predicted participants would provide event narratives of high veracity, future events (particularly those occurring in the distant future) were expected to receive lower veracity ratings than past events due to the uncertainty inherent in future occurrences. It is challenging to assess the episodic content of children's event narratives because age differences could reflect changes in reporting skills or language ability rather than true changes in experience. We attempted to address this issue by using a coding scheme (adapted from Piolino et al., 2007) that assessed episodic content independent of narrative length (i.e., credit was given for referencing any spatial or temporal element of an event regardless of amount of elaboration associated with that element). Furthermore, narrative length was coded so that we could account for this variable in explaining episodicity. We predicted that children's ability to provide both past and future event narratives of high episodicity (i.e., positioned in space/time and including other contextual detail) would improve across middle childhood due to presumed commonalities in the mechanisms underlying episodic memory and prospection. Based on findings with adults (Addis et al., 2007), we also predicted an effect of temporal direction such that the episodicity of past event narratives would be higher than that of future event narratives. We also predicted that age-related improvements in the episodicity of future event narratives would be more protracted than age-related improvements in the episodicity of past event narratives. Since prospection is thought to involve accessing and recombining details from multiple past experiences (Schacter and Addis, 2007a and Schacter and Addis, 2007b), we reasoned that it may be particularly challenging for children given that they have less flexible retrieval than adults (Ackerman, 1982 and Paz-Alonso et al., 2009). Finally, the episodicity of temporally close event narratives was expected to be higher than that of temporally distant event narratives given previous findings with adults (D’Argembeau & Van der Linden, 2004). To assess the subjective experience of episodicity, we asked participants to provide ratings of their mental experience during each event mentalization. These included: (a) degree of clarity with which the event was envisioned, (b) whether the event was envisioned from a first- or third-person visual perspective, and (c) how easy it was to think of the event. A rich subjective experience should be associated with higher ratings of event clarity, first-person visual perspective, and ease of thinking of the event (Berntsen and Rubin, 2006, Sutin and Robins, 2008, Tulving, 1972, Tulving, 1985 and Tulving, 2005). To the extent that these phenomenological dimensions are equally represented in episodic memory and prospection, they should be similarly affected by the temporal distance manipulation. Conversely, a differential effect by temporal direction would suggest that the cognitive processes underlying these ratings may contribute uniquely or differently to past versus future mentalizing. One might also anticipate different effects of our independent variables on introspective ratings based on studies showing dissociations among metacognitive judgments about episodic recollection (Metcalfe and Finn, 2008 and Finn, 2008) and prospection (D’Argembeau & Van der Linden, 2012). We make no predictions regarding these types of dissociations but note that findings could reveal something unique about the subjective experience of episodic memory and prospection. Finally, we expected that participants in all age groups would be able to report on event clarity and ease of thinking given that 4–5-year-olds can evaluate the quality of memory representations in terms of amount of memory detail and can make confidence judgments (Ghetti and Alexander, 2004 and Ghetti et al., 2002). We also anticipated that young children would be able to report on visual perspective if it is a fundamental aspect of their subjective experience. However, if a manipulation of visual imagery is needed to establish and attribute visual perspective, younger children may exhibit poorer skills reporting visual perspective compared to other introspective aspects (Kosslyn, Margolis, Goldknopf, Daly, & Barrett, 1990). Furthermore, some developmental differences across ratings were expected given evidence that introspection on memory states improves during middle childhood (Ghetti et al., 2008, Ghetti et al., 2011, Roebers and Howie, 2003 and Roebers, 2002).