Memories of the Future: New Insights into the Adaptive Value of Episodic Memory

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Citation Szpunar, Karl K., Donna Rose Addis, Victoria C. McLelland, and Daniel L. Schacter. 2013. “Memories of the Future: New Insights into the Adaptive Value of Episodic Memory.” Frontiers in Behavioral Neuroscience 7 (1): 47. doi:10.3389/fnbeh.2013.00047. http:// dx.doi.org/10.3389/fnbeh.2013.00047.

Published Version doi:10.3389/fnbeh.2013.00047

Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:11708605

Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Other Posted Material, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#LAA Opinion Article published: 23 May 2013 BEHAVIORAL NEUROSCIENCE doi: 10.3389/fnbeh.2013.00047 Memories of the future: new insights into the adaptive value of episodic memory

Karl K. Szpunar 1,2*, Donna Rose Addis 3,4, Victoria C. McLelland 3,4 and Daniel L. Schacter 1,2

1 Department of Psychology, Harvard University, Cambridge, MA, USA 2 Center for Brain Science, Harvard University, Cambridge, MA, USA 3 School of Psychology, The University of Auckland, Auckland, New Zealand 4 Centre for Brain Research, The University of Auckland, Auckland, New Zealand *Correspondence: [email protected] Edited by: Hans J. Markowitsch, University of Bielefeld, Germany Reviewed by: Hans J. Markowitsch, University of Bielefeld, Germany Katharina Schnitzspahn, University of Geneva, Switzerland

Ingvar (1979, p. 21) theorized that memory (1) enhanced memory for event details that ing trip, or imagining a typical ­campsite plays a key role in allowing individuals to are encoded with the future in mind, (2) without reference to the past or future. construct “alternative hypothetical behavior factors that may influence the retention of During the simulation/retrieval task, par- patterns in order to be ready for what may simulated future events over extended time ticipants were asked to indicate how likely happen,” a process that he characterized as a periods, and (3) neural correlates associated it was that various items (e.g., tent, rope) “simulation of behavior”. Several years later, with encoding simulated future events. were incorporated into their self-generated Ingvar elaborated these ideas by observing Next, we provide a brief overview of this scenarios. After a brief delay, participants that “concepts about the future, like mem- emerging line of research, underscore the were presented with a blank sheet of paper ories of past events, can be remembered, significance of various findings along with and asked to recall the list of items asso- often in great detail” (Ingvar, 1985, p. 128), suggestions for future research directions, ciated with the simulation/retrieval task. and that such “memories of the future” may and conclude by discussing the relevance Participants who had simulated a future offer important insights into the adaptive of this work to the concept of episodic camping trip remembered more items than nature of human cognition. For instance, memory. As we expand on below, it is our participants who had remembered a camp- although the ability to simulate alternative opinion that these new studies represent not ing trip or simulated a typical campsite in versions of the future can benefit behavior, only a useful extension of Ingvar’s (1979, an atemporal manner. at least part of the adaptive advantage of 1985) seminal observations, but that they Notably, Klein et al. (2010) included future thinking may depend on the abil- also offer novel insights into the adaptive a fourth encoding condition that asked a ity to remember the contents of simulated value of episodic memory. separate group of participants to imagine events (for discussion, see Suddendorf a hypothetical camping scenario in which and Corballis, 1997, 2007; Szpunar, 2010; Future-Oriented Encoding they were stranded in a forest, and to indi- Schacter, 2012; Schacter et al., 2012). As Processes Enhance Retention cate how likely it was that the same set an example, enlisting mental simulations Klein et al. (2012, p. 240) have recently of items (e.g., tent, rope) would enhance of the future to help determine the best noted that systems of memory, includ- their chances of survival. This latter condi- approach for resolving a conflict at home ing episodic memory, may be “designed tion was included in response to a recent or in the workplace may confer few advan- by evolution to interface with systems of series of studies by Nairne and colleagues tages if the outcome of the simulation long-term planning” (see also Suddendorf demonstrating that attending to the sur- process is not remembered at the time the and Corballis, 2007). Accordingly, memory vival value of to-be-encoded information simulated behavior is executed. Although systems should be more efficient in dealing also enhances retention relative to other much research exists concerning prospec- with encoding manipulations that encour- well-established encoding manipulations tive memory – remembering to carry out age future-oriented processes such as plan- (for a review, see Nairne, 2010). Klein et al. future intentions (e.g., Kliegel et al., 2008; ning than other well-established encoding (2010) hypothesized that survival process- see also Brewer and Marsh, 2009) – there is a manipulations that are not necessarily ori- ing may enhance retention to the extent that striking lack of evidence concerning “mem- ented toward the future (e.g., imagery, self- it calls upon future-oriented processes such ory of the future” in the sense discussed by relevance; see also Klein et al., 2002; Klein as planning. Along these lines, Klein et al. Ingvar, that is, memory for the contents of et al., 2010; McDonough and Gallo, 2010). (2010) further suggested that the survival future simulations. Recently, however, sev- A recent line of research supports this pre- scenario might evoke planning in some par- eral studies have provided the first glimpses diction. Klein et al. (2010) asked separate ticipants but not others; for instance, some into how well people remember details groups of participants to think about one of participants may think about the survival associated with simulated future events. In three camping scenarios: imagining a future scenario in an atemporal manner. Hence, particular, these studies have demonstrated camping trip, remembering a past camp- while details associated with the survival

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scenario should be better remembered than operations (for a review, see Johnson, scenarios comprising people, ­locations, details associated with scenarios that do not 1988). Building on the results of Johnson and objects that had been extracted from evoke planning (e.g., remembering a camp- and others, McDonough and Gallo (2010) autobiographical memories or participant- ing trip), details associated with the sur- found that people were able to make use of generated lists. Memory for simulations vival scenario should not be remembered phenomenological characteristics such as was tested either shortly after simulation as well as details associated with scenarios perceptual clarity and cognitive operations (20 min) or after an extended delay (24 h) that always evoke planning (e.g., imagining when discriminating between memories by providing two elements of the simu- a future camping trip). Klein et al. (2010) of past and future events. Interestingly, the lated episode (e.g., person and object) and found support for both of these predictions. authors also found that the distinguishing probing for recall of the third element In a subsequent study, Klein et al. (2011) characteristics of future events – cognitive (e.g., location). Interestingly, more emo- systematically varied the involvement of operations – were more diagnostic in dis- tional simulations (i.e., positive and nega- planning and survival processing in vari- criminating between memories of past and tive events) were remembered than neutral ous simulated scenarios, and found that future events than were the distinguishing simulations after the short delay, whereas participants were better able to remember characteristics of memories – perceptual­ more positive and neutral simulations were details associated with scenarios that had clarity. Accordingly, McDonough and remembered than negative simulations after evoked planning, whether or not survival Gallo (2010) noted that this latter pattern the long delay. That is, negative simulations processing was relevant, than details asso- of results might reflect the workings of a were forgotten more quickly than positive ciated with survival scenarios that had not memory system whose primary function and neutral simulations. This pattern of evoked planning. involves “imagination and planning for data may reflect the influence of fading Nonetheless, some studies have failed future events” (p. 7). affect bias (Walker and Skowronski, 2009), to demonstrate a mnemonic advantage for In sum, the results of a number of studies such that the affect that binds event details encoding conditions that foster planning have demonstrated that encoding manipu- together (Mather and Sutherland, 2011) as compared to survival processing (e.g., lations that encourage future-oriented pro- may dissipate more quickly for negative Kang et al., 2008; Weinstein et al., 2008). cesses such as planning improve retention than positive events. Notably, Gallo et al. In response to these incongruent findings, relative to other well-established encoding (2011) also found a positivity bias in mem- Klein et al. (2010, 2011) pointed out that manipulations. Moving forward, studies ory for simulated future events after 24 h in enhanced memory for plans might depend that can identify the possible factors that young and old adults. Hence, the available on the extent to which plans evoke concepts underlie the mnemonic advantage associ- data suggests that people may remember a of the personal future, such as planning for ated with future-oriented encoding pro- rosy simulated future. Further studies of events that participants have experienced cesses, such as the role of familiarity and memory for simulated emotional events in the past and expect to experience again personal experience (Klein et al., 2012), will may thus have the potential to provide in the future. To test this claim, Klein et al. be of considerable interest. As an initial step insights into various mood disorders such (2012) asked separate groups of partici- in that direction, McLelland et al. (submit- as anxiety and depression. pants to plan for familiar (e.g., dinner party) ted) identified several event characteristics and unfamiliar (e.g., trip to Antarctica) sce- that predicted the likelihood of successful Neural Substrates for Encoding narios. Participants who had made plans for encoding of future events. Imagined future Simulations of Future Events familiar scenarios remembered more details events that were rated by participants as So far, studies concerning “memory of the associated with those scenarios than partici- being more detailed, more plausible, and future” have focused mainly on cognitive pants who had made plans for unfamiliar involving more familiar elements (in par- processes. Although little is known about scenarios. ticular, events with more familiar people) the neural processes that support encod- Hence, the available evidence suggests were all significantly more likely to be later ing of simulated future events, a recent that people are rather adept at encoding and remembered than imagined events with low study by Martin et al. (2011) indicates that subsequently remembering details about ratings on such characteristics. the hippocampus plays an important role. simulated future events. We conclude this During fMRI scanning, participants imag- section by discussing a recent study demon- Retention of Simulated Future ined future scenarios comprising people, strating how enhanced memory for details Events Over Extended Periods locations, and objects that were extracted associated with future events can be used to In the studies discussed thus far, memory from autobiographical memories. Memory help people distinguish between memories for future simulations was tested after for simulations was tested shortly after the of the past and future. Earlier research on relatively brief study-test delays (usually scan by providing two elements of the simu- the relation between memory and imagi- 5–20 min post simulation). Yet in the eve- lated episode (e.g., person and object) and nation had demonstrated that memories ryday situations discussed by Ingvar (1985), probing for recall of the third element (e.g., and simulated events are best character- it may be necessary to retain a simulation location); a simulation was classified as ized by distinct phenomenological features: over days and weeks. However, only two “remembered” when participants recalled remembered events tend to be character- studies of which we are aware have exam- the third element correctly, and “forgotten” ized by enhanced perceptual clarity whereas ined memory for simulated future events at when they did not. Greater hippocampal imagined events tend to be characterized extended delays. In one study, Szpunar et al. activity was observed during construction by increased representation of cognitive (2012) asked participants to imagine future of subsequently remembered than ­forgotten

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simulations even when controlling for the Brewer, G. A., and Marsh, R. L. (2009). On the role of Nairne, J. S. (2010). “Adaptive memory: evolutionary amount of detail associated with each episodic future simulation in encoding of prospective constraints on remembering,” in The Psychology of memories. Cogn. Neurosci. 1, 81–88. simulation (for discussion of related find- Learning and Motivation, ed. B. H. Ross (London: Gallo, D. A., Korthauer, L. E., McDonough, I. M., Teshale, S., Academic Press), 1–32. ings, see Addis and Schacter, 2012; Schacter and Johnson, E. L. (2011). Age-related positivity effects Schacter, D. L. (2012). Adaptive constructive processes et al., 2012). Looking ahead, studies will be and autobiographical memory detail: evidence from a and the future of memory. Am. Psychol. 67, 603–613. needed that can isolate the neural circuitry past/future source memory task. Memory 19, 641–652. Schacter, D. L., Addis, D. R., Hassabis, D., Martin, V. C., that underlies the mnemonic advantage Ingvar, D. H. (1979). “Hyperfrontal” distribution of the Spreng, R. N., and Szpunar, K. K. (2012). The future cerebral grey matter flow in resting wakefulness: on of memory: remembering, imagining, and the brain. produced by encoding information with the functional anatomy of the conscious state. Acta Neuron 76, 677–694. the future in mind. Neurol. Scand. 60, 12–25. Suddendorf, T., and Corballis, M. C. (1997). Mental time Ingvar, D. H. (1985). “Memory of the future”: an essay travel and the evolution of the human mind. Genet. Summary and Conclusions on the temporal organization of conscious awareness. Soc. Gen. Psychol. Monogr. 123, 133–167. Over the last four decades, the concept of Hum. Neurobiol. 4, 127–136. Suddendorf, T., and Corballis, M. C. (2007). The Johnson, M. K. (1988). Reality monitoring: an experi- evolution of foresight: what is mental time travel, episodic memory has evolved into a mul- mental phenomenological approach. J. Exp. Psychol. and is it unique to humans? Behav. Brain Sci. 30, tifaceted construct that is of great interest Gen. 117, 390–394. 299–313. to researchers in various areas of psychol- Kang, S. H. K., McDermott, K. B., and Cohen, S. M. Szpunar, K. K. (2010). Episodic future thought: an emerg- ogy and neuroscience (for recent over- (2008). The mnemonic advantage of process- ing concept. Perspect. Psychol. Sci. 5, 142–162. views, see Szpunar and McDermott, 2008; ing fitness-relevant information. Mem. Cognit. 36, Szpunar, K. K., Addis, D. R., and Schacter, D. L. (2012). 1151–1156. Memory for emotional simulations: remembering a Tulving and Szpunar, 2009). Here, we have Klein, S. B., Cosmides, L., Tooby, J., and Chance, S. (2002). rosy future. Psychol. Sci. 23, 24–29. highlighted recent insights into an adaptive Decisions and the evolution of memory: multiple sys- Szpunar, K. K., and McDermott, K. B. (2008). “Episodic feature of episodic memory first noted by tems, multiple functions. Psychol. Rev. 109, 306–329. memory: an evolving concept,” in Cognitive Psychology Ingvar (1985): “memories of the future,” like Klein, S. B., Robertson, T. E., and Delton, A. W. (2010). of Memory, Vol. 2 of Learning and Memory: A Facing the future: memory as an evolved system for memories of past events, can help to guide Comprehensive Reference, eds H. L. Roediger and J. planning future acts. Mem. Cognit. 38, 13–22. H. Byrne (Oxford: Elsevier), 491–509. behavior. Given the potential theoretical Klein, S. B., Robertson, T. E., and Delton, A. W. (2011). Tulving, E., and Szpunar, K. K. (2009). Episodic memory. and practical importance of understanding The future-orientation of memory: planning as a key Scholarpedia 4, 3332. memories of the future, it is perhaps sur- component mediating the high levels of recall found Walker, W. R., and Skowronski, J. J. (2009). The fading prising that so little relevant experimental­ with survival processing. Memory 19, 121–139. affect bias: but what the hell is it for? Appl. Cogn. Klein, S. B., Robertson, T. E., Delton, A. W., and Lax, M. L. Psychol. 23, 1122–1136. work has been done. Developing a more (2012). Familiarity and personal experience as media- Weinstein, Y., Bugg, J. M., and Roediger, H. L. (2008). in depth understanding of why simulated tors of recall when planning for future contingencies. Can the survival recall advantage be explained by future events are well remembered, what J. Exp. Psychol. Learn. Mem. Cogn. 38, 240–245. basic memory processes? Mem. Cognit. 36, 913–919. factors influence the long-term retention Kliegel, M., McDaniel, M. A., and Einstein, G. O. of simulated future events, and how the (2008). Prospective Memory: Cognitive, Neuroscience, Developmental, and Applied Perspectives. Mahwah, Received: 11 March 2013; accepted: 03 May 2013; published brain supports the encoding of simulated NJ: Erlbaum. online: 23 May 2013. future events, represent important avenues Martin, V. C., Schacter, D. L., Corballis, M. C., and Addis, Citation: Szpunar KK, Addis DR, McLelland VC and for future research that are likely to broaden D. R. (2011). A role for the hippocampus in encod- Schacter DL (2013) Memories of the future: new insights our understanding of the utility of episodic ing simulations of future events. Proc. Natl. Acad. Sci. into the adaptive value of episodic memory. Front. Behav. memory in everyday life. U.S.A. 108, 13858–13863. Neurosci. 7:47. doi: 10.3389/fnbeh.2013.00047 Mather, M., and Sutherland, M. R. (2011). Arousal-biased Copyright © 2013 Szpunar, Addis, McLelland and Schacter. competition in perception and memory. Perspect. This is an open-access article distributed under the terms References Psychol. Sci. 6, 114–133. of the Creative Commons Attribution License, which per- Addis, D. R., and Schacter, D. L. (2012). The hip- McDonough, I. M., and Gallo, D. A. (2010). Separating mits use, distribution and reproduction in other forums, pocampus and imagining the future: where do we past and future autobiographical events in memory: provided the original authors and source are credited and stand? Front. Hum. Neurosci. 5:173. doi: 10.3389/ evidence for a reality monitoring asymmetry. Mem. subject to any copyright notices concerning any third-party fnhum.2011.00173 Cognit. 38, 3–12. graphics etc.

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