Memory without content? Radical enactivism and (post)causal theories of memory

Abstract

Radical enactivism, an increasingly influential approach to cognition in general, has recently been applied to memory in particular, with Hutto and Peeters (in: Michaelian and Debus (eds) New directions in the philosophy of memory, Routledge, New York, 2018) providing the first systematic discussion of the implications of the approach for mainstream philosophical theories of memory. Hutto and Peeters argue that radical enactivism, which entails a conception of memory traces as contentless, is fundamentally at odds with current causal and postcausal theories, which remain committed to a conception of traces as contentful: on their view, if radical enactivism is right, then the relevant theories are wrong. Partisans of the theories in question might respond to Hutto and Peeters’ argument in two ways. First, they might challenge radical enactivism itself. Second, they might challenge the conditional claim that, if radical enactivism is right, then their theories are wrong. In this paper, we develop the latter response, arguing that, appearances to the contrary notwithstanding, radical enactivism in fact aligns neatly with an emerging tendency in the philosophy of memory: radical enactivists and causal and postcausal theorists of memory have begun to converge, for distinct but compatible reasons, on a contentless conception of memory traces.

This is a preview of subscription content, access via your institution.

Notes

  1. 1.

    Our focus here will be exclusively on radical enactivism, and we will have nothing to say about the implications of other forms of enactivism for the philosophy of memory. Hutto and Myin (2013) argue that “sensorimotor enactivism” (Hurley 1998; O’Regan and Noë 2001; Noë 2004) takes perception to be a matter of embodied action but does not entirely give up on the idea that perception is representational, while “autopoeitic enactivism” (Varela et al. 1991; Thompson 2007) relies on metaphors (e.g., “interpretation”, “sense-making”) that are often understood in representational terms. Radical enactivism, we take it, is meant to differ from these other enactivist approaches in that it attempts to break entirely with the view that cognition involves representation.

  2. 2.

    Radical enactivism has been the target of a number of objections (see Myin and Hutto 2015). Some have objected that, given the entrenched status of the concept of content in philosophy and its explanatory utility in cognitive science, radical enactivists have not provided sufficient reason for abandoning it (Campbell 2014; Shapiro 2014; Colombo 2014). Others have objected that radical enactivists have not adequately taken concepts of representation that do not appeal to accuracy conditions into account (Roberts 2013; Gładziejewski 2015). And others have objected that radical enactivists have not provided clear positive accounts of specific forms of cognition, as opposed to negative arguments against representationalist accounts (Shapiro 2014). The account of remembering proposed by Hutto and Peeters can be seen as providing a partial response to the last of these objections.

  3. 3.

    Hutto and Peeters read De Brigard as endorsing a contentless conception of traces. Though he does not explicitly make this claim, we will not challenge their reading here.

  4. 4.

    With respect to the first body of theory, we focus on extended rather than embodied aspects of remembering. This is in keeping with Hutto and Peeters’ own focus.

  5. 5.

    Since our focus here is on radical enactivism, we will have nothing to say about the relationship between Hutto and Peeters’ argument for NC and historical attacks on contentful traces. For background on this history, see chapter 16 of Sutton 1998.

  6. 6.

    See Robins 2016b for detailed discussion of the relationship between connectionist networks and networks of the kind thought to be involved in memory.

  7. 7.

    In order to avoid terminological confusion, we note that, while Hutto and Peeters (like Perrin 2018; see Sect. 4) would prefer not to refer to memory traces at all, this is because they take it a contentful conception of traces for granted; they would presumably be willing to refer to traces on the condition that these are understood in line with the contentless conception outlined below.

  8. 8.

    This project is motivated, in turn, by the claims, first, that there is no naturalistically respectable account of content available (the so-called “hard problem of content”) and, second, that eliminating reference to content in cognitive science does not result in loss of explanatory power (Hutto and Myin 2013, 2017).

  9. 9.

    The literature in question is voluminous, and we will not attempt to duplicate De Brigard’s summary and interpretation of it here.

  10. 10.

    One might object here that a disposition to produce a certain content is naturally viewed as carrying that content. While it is not our aim here to defend Hutto and Peeters’ move from the distributed conception to the contentless conception, we note that the obvious response to this objection is to point out that the issue is about storage of content and that a disposition is simply not the sort of entity that might store content. One might further object that the notion of a contentless trace is unintuitive and that a much more detailed statement of the contentless conception is required before radical enactivism about memory can be properly assessed. While our project here, which is concerned with the relationships among existing theories rather than with developing those theories in further detail, does not require us to undertake this, we acknowledge that radical enactivists (and procedural causal and nontransmissionist simulation theorists; see Sect. 4) will eventually need to develop the contentless conception in more detail.

  11. 11.

    Just as we do not aim to assess the viability of radical enactivism, we do not aim to assess that of the causal theory or the other theories of memory discussed below.

  12. 12.

    Shanton and Goldman (2010) and De Brigard (2014) defend simulationist accounts of remembering but, unlike Michaelian, do not explicitly deal with the question of the necessity of appropriate causation. In addition to the simulation theory, the category of postcausal theories includes Fernández’ (2018) functionalist theory and, arguably, James’ (2017) version of the epistemic theory.

  13. 13.

    See Perrin and Michaelian 2017 and Sant’Anna 2018 for reviews.

  14. 14.

    This argument takes the mental time travel framework for granted and, moreover, rests on a “continuist” interpretation of that framework according to which it implies that, aside from their different temporal orientations, there is no difference in kind between episodic memory and episodic future thought. For alternative “discontinuist” interpretations of the mental time travel framework, see Perrin 2016 and Dokic and Arcangeli 2018. For an argument against the framework itself, see Mahr and Csibra 2018.

  15. 15.

    This slowness may be due to a failure on the part of philosophers of memory to take older debates over the storage of content in connectionist networks—in which some (e.g., Ramsey et al. 1990) argued that the lack of storage of explicit content in such networks meant that they simply did not store content, while others (e.g., O’Brien 1991) argued that they might nevertheless store implicit content—into account.

  16. 16.

    See Robins 2016a for a recent approach in the same general spirit.

  17. 17.

    One might worry here that the puzzle analogy allows the procedural causal theorist to smuggle into his account the very (componential) content that he rejects (in the form of the puzzle pieces). The procedural causal theorist would presumably argue, in response, that the components of the content of the retrieved representation are generated at the time of retrieval by the reactivation of areas that were activated during experience.

  18. 18.

    In addition to Perrin (2018) and De Brigard (2014), Robins (2016b) and Cheng and Werning (2016) have hinted at the necessity for a contentless conception of traces. Going further back, there are few clear discussions of the issue, though Vosgerau (2010) does presage recent developments in some respects.

  19. 19.

    The preservationism/generationism debate is multifaceted, and “preservationism” and “generationism” have been used to refer to a variety of pairs of views related to but distinct from those discussed here. See, e.g., Fernández (2016) on whether episodic memory generates (second-order) knowledge of the source of one’s (first-order) knowledge in past experience (cf. Dokic 2014) and Lackey (2005) and Senor (2007) on whether memory generates knowledge via the coming and going of defeaters. Frise (2017) and Bernecker and Grundmann (forthcoming) discuss additional varieties of preservationism/generationism.

  20. 20.

    A comparison of the transmissionist and nontransmissionist versions of the anti-sufficiency argument suggests two observations. The first is that distributed and procedural causal theorists have yet to really offer an account of appropriate causation. Given the local conception of traces, there might in principle be a one-to-one correspondence between traces and experiences, even if, in practice, there is always always a one-to-many correspondence. Given the distributed conception, in contrast, there is a one-to-many correspondence virtually by definition. The second is that, while the one-to-many correspondence between traces and experiences ensures that the the nontransmissionist simulationist can come to the same conclusion as the transmissionist simulationist regarding the insufficiency of appropriate causation, the structure of the nontransmissionist anti-sufficiency argument does not precisely mirror that of the transmissionist anti-sufficiency argument. The latter turns on the claim that distinct contents originating in experiences of distinct events can make their way into a single retrieved memory. The former replaces this claim with the claim that retrieval of a single memory can be treated as the activation of a disposition originating in experiences of distinct events. In order for the nontransmissionist argument to mirror the transmissionist argument, it would need, instead, to appeal to the claim that retrieval of a single memory can be treated as the activation of distinct dispositions originating in experiences of distinct events. Whether this claim is coherent cannot be determined without a more detailed discussion of the nature of the relevant dispositions than we can feasibly undertake here.

  21. 21.

    If we deny the possibility of such cases, insisting that there is always a causal connection, then the necessity condition collapses into triviality.

  22. 22.

    See Michaelian (2016a), forthcoming for a response.

  23. 23.

    That the procedural causal theory and the simulation theory are both compatible with radical enactivism about memory does not imply that there is no significant disagreement between them: the procedural causal theory remains a causal theory, and the procedural causal theorist will need to find a way of resisting (the nontransmissionist versions of) the simulation theorist’s anti-necessity and anti-sufficiency arguments.

  24. 24.

    Strictly speaking, Michaelian’s view is that the fundamental distinction is between “cognitive” and “noncognitive” memory, terms that do not map precisely on to “declarative” and “nondeclarative”. This subtlety does not affect our argument.

  25. 25.

    One might wonder whether a nontransmissionist simulation theorist can really say everything that Michaelian says in the passage quoted on page 14. The same thing goes for nontransmissionist theorists in general: it is unclear how a procedural causal theorist, for example, can say everything that we need to say about the ways in which memory feeds into other cognitive processes and leads to behaviour without making any reference at all to stored content. We grant that this is unclear and indeed take it to be a major challenge for nontransmissionism. Our goal in this section, however, has not been to show how nontransmissionists might meet that challenge but only (more modestly) to show how they might coherently adopt something like Michaelian’s approach to the taxonomy of memory.

References

  1. Adams, F., & Aizawa, K. (2008). The bounds of cognition. Hoboken: Wiley.

    Google Scholar 

  2. Arcangeli, M. (2018). Supposition and the imaginative realm: A philosophical inquiry. New York: Routledge.

    Google Scholar 

  3. Bernecker, S. (2010). Memory: A philosophical study. Oxford: Oxford University Press.

    Google Scholar 

  4. Bernecker, S. (2017). A causal theory of mnemonic confabulation. Frontiers in Psychology, 8, 1207.

    Google Scholar 

  5. Bernecker, S., & Grundmann, T. (forthcoming). Knowledge from forgetting. Philosophy and Phenomenological Research.

  6. Byrne, A. (2010). Recollection, perception, imagination. Philosophical Studies, 148(1), 15–26.

    Google Scholar 

  7. Campbell, D. (2014). Review of the book Radicalizing Enactivism by D. D. Hutto and E. Myin. Analysis, 74, 174–176.

    Google Scholar 

  8. Cheng, S., & Werning, M. (2016). What is episodic memory if it is a natural kind? Synthese, 193(5), 1345–1385.

    Google Scholar 

  9. Clark, A., & Chalmers, D. (1998). The extended mind. Analysis, 58(1), 7–19.

    Google Scholar 

  10. Colombo, M. (2014). Explaining social norm compliance. A plea for neural representations. Phenomenology and the Cognitive Sciences, 13(2), 217–238.

    Google Scholar 

  11. De Brigard, F. (2014). Is memory for remembering? Recollection as a form of episodic hypothetical thinking. Synthese, 191(2), 155–185.

    Google Scholar 

  12. Debus, D. (2008). Experiencing the past: A relational account of recollective memory. Dialectica, 62(4), 405–432.

    Google Scholar 

  13. Debus, D. (2017). Memory causation. In S. Bernecker & K. Michaelian (Eds.), The Routledge handbook of philosophy of memory (pp. 63–75). New York: Routledge.

    Google Scholar 

  14. Dokic, J. (2014). Feeling the past: A two-tiered account of episodic memory. Review of Philosophy and Psychology, 5(3), 413–426.

    Google Scholar 

  15. Dokic, J., & Arcangeli, M. (2018). Affective memory: A little help from our imagination. In K. Michaelian, D. Debus, & D. Perrin (Eds.), New directions in the philosophy of memory (pp. 139–157). Abingdon-on-Thames: Routledge.

    Google Scholar 

  16. Fernández, J. (2016). Epistemic generation in memory. Philosophy and Phenomenological Research, 92(3), 620–644.

    Google Scholar 

  17. Fernández, J. (2018). The functional character of memory. In K. Michaelian, D. Debus, & D. Perrin (Eds.), New directions in the philosophy of memory (pp. 52–72). New York: Routledge.

    Google Scholar 

  18. Fivush, R. (2011). The development of autobiographical memory. Annual Review of Psychology, 62, 559–582.

    Google Scholar 

  19. Fivush, R., & Nelson, K. (2004). Culture and language in the emergence of autobiographical memory. Psychological Science, 15(9), 573–577.

    Google Scholar 

  20. Frise, M. (2017). Preservationism in the epistemology of memory. The Philosophical Quarterly, 67(268), 486–507.

    Google Scholar 

  21. Genone, J. (2014). Appearance and illusion. Mind, 123(490), 339–376.

    Google Scholar 

  22. Gładziejewski, P. (2015). Explaining cognitive phenomena with internal representations: A mechanistic perspective. Studies in Logic, Grammar and Rhetoric, 40(1), 63–90.

    Google Scholar 

  23. Goldman, A. (2006). Simulating minds: The philosophy, psychology, and neuroscience of mindreading. Oxford: Oxford University Press.

    Google Scholar 

  24. Hoerl, C. (2007). Episodic memory, autobiographical memory, narrative: On three key notions in current approaches to memory development. Philosophical Psychology, 20(5), 621–640.

    Google Scholar 

  25. Hurley, S. (1998). Consciousness in action. Cambridge: Harvard University Press.

    Google Scholar 

  26. Hutto, D. D. (2017). Memory and narrativity. In S. Bernecker & K. Michaelian (Eds.), The Routledge handbook of philosophy of memory (pp. 192–204). New York: Routledge.

    Google Scholar 

  27. Hutto, D. D., & Myin, E. (2013). Radicalizing enactivism: Basic minds without content. Cambridge: MIT Press.

    Google Scholar 

  28. Hutto, D. D., & Myin, E. (2017). Evolving enactivism: Basic minds meet content. Cambridge: MIT Press.

    Google Scholar 

  29. Hutto, D. D., & Peeters, A. (2018). The roots of remembering: Radically enactive recollecting. In K. Michaelian, D. Debus, & D. Perrin (Eds.), New directions in the philosophy of memory (pp. 97–118). New York: Routledge.

    Google Scholar 

  30. Intraub, H., Bender, R. S., & Mangels, J. A. (1992). Looking at pictures but remembering scenes. Journal of Experimental Psychology: Learning, Memory, and Cognition, 18(1), 180–191.

    Google Scholar 

  31. Irish, M. (2016). Semantic memory as the essential scaffold for future-oriented mental time travel. In K. Michaelian, S. B. Klein, & K. K. Szpunar (Eds.), Seeing the future: Theoretical perspectives on future-oriented mental time travel (pp. 389–408). Oxford: Oxford University Press.

    Google Scholar 

  32. James, S. (2017). Epistemic and non-epistemic theories of remembering. Pacific Philosophical Quarterly, 98, 109–127.

    Google Scholar 

  33. Klein, S. B. (2015). What memory is. Wiley Interdisciplinary Reviews: Cognitive Science, 6(1), 1–38.

    Google Scholar 

  34. Klein, S. B., Loftus, J., & Kihlstrom, J. F. (2002). Memory and temporal experience: The effects of episodic memory loss on an amnesic patient’s ability to remember the past and imagine the future. Social Cognition, 20(5), 353–379.

    Google Scholar 

  35. Lackey, J. (2005). Memory as a generative epistemic source. Philosophy and Phenomenological Research, 70(3), 636–658.

    Google Scholar 

  36. Loader, P. (2013). Is my memory an extended notebook? Review of Philosophy and Psychology, 4(1), 167–184.

    Google Scholar 

  37. Mahr, J. B., & Csibra, G. (2018). Why do we remember? The communicative function of episodic memory. Behavioral and Brain Sciences, 41, e1.

    Google Scholar 

  38. Martin, C. B., & Deutscher, M. (1966). Remembering. The Philosophical Review, 75(2), 161–196.

    Google Scholar 

  39. Michaelian, K. (2011). Generative memory. Philosophical Psychology, 24(3), 323–342.

    Google Scholar 

  40. Michaelian, K. (2012). Is external memory memory? Biological memory and extended mind. Consciousness and Cognition, 21(3), 1154–1165.

    Google Scholar 

  41. Michaelian, K. (2015). Opening the doors of memory: Is declarative memory a natural kind? Wiley Interdisciplinary Reviews: Cognitive Science, 6(6), 475–482.

    Google Scholar 

  42. Michaelian, K. (2016). Confabulating, misremembering, relearning: The simulation theory of memory and unsuccessful remembering. Frontiers in Psychology, 7, 1857.

    Google Scholar 

  43. Michaelian, K. (2016). Mental time travel: Episodic memory and our knowledge of the personal past. Cambridge: MIT Press.

    Google Scholar 

  44. Michaelian, K. (2018). Episodic and semantic memory and imagination: The need for definitions. American Journal of Psychology, 131(1), 99–103. Review essay on M. S. Humphreys and K. A. Chalmers, Thinking about Human Memory.

    Google Scholar 

  45. Michaelian, K. (forthcoming). Confabulating as unreliable imagining: In defence of the simulationist account of unsuccessful remembering. Topoi.

  46. Michaelian, K., Perrin, D., & Sant’Anna, A. (forthcoming). Continuities and discontinuities between imagination and memory: The view from philosophy. In A. Abraham, (Ed.), The Cambridge handbook of imagination. Cambridge University Press.

  47. Michaelian, K., & Robins, S. K. (2018). Beyond the causal theory? Fifty years after Martin and Deutscher. In K. Michaelian, D. Debus, & D. Perrin (Eds.), New directions in the philosophy of memory (pp. 13–32). New York: Routledge.

    Google Scholar 

  48. Myin, E., & Hutto, D. D. (2015). REC: Just radical enough. Studies in Logic, Grammar and Rhetoric, 41(1), 61–71.

    Google Scholar 

  49. Nelson, K., & Fivush, R. (2004). The emergence of autobiographical memory: A social cultural developmental theory. Psychological Review, 111(2), 486.

    Google Scholar 

  50. Noë, A. (2004). Action in perception. Cambridge: MIT Press.

    Google Scholar 

  51. O’Brien, G. J. (1991). Is connectionism commonsense? Philosophical Psychology, 4(2), 165–178.

    Google Scholar 

  52. O’Regan, J. K., & Noë, A. (2001). A sensorimotor account of vision and visual consciousness. Behavioral and Brain Sciences, 24(5), 939–973.

    Google Scholar 

  53. Perrin, D. (2016). Asymmetries in subjective time. In K. Michaelian, S. B. Klein, & K. K. Szpunar (Eds.), Seeing the future: theoretical perspectives on future-oriented mental time travel (pp. 39–61). Oxford: Oxford University Press.

    Google Scholar 

  54. Perrin, D. (2018). A case for procedural causality in episodic recollection. In K. Michaelian, D. Debus, & D. Perrin (Eds.), New directions in the philosophy of memory (pp. 33–51). New York: Routledge.

    Google Scholar 

  55. Perrin, D., & Michaelian, K. (2017). Memory as mental time travel. In S. Bernecker & K. Michaelian (Eds.), The Routledge handbook of philosophy of memory (pp. 228–239). New York: Routledge.

    Google Scholar 

  56. Ramsey, W., Stich, S., & Garan, J. (1990). Connectionism, eliminativism, and the future of folk psychology. In D. J. Cole, J. H. Fetzer, & T. L. Rankin (Eds.), Philosophy, mind, and cognitive inquiry: Resources for understanding mental processes (pp. 117–144). Berlin: Springer.

    Google Scholar 

  57. Roberts, T. (2013). Review of Radicalizing enactivism by D. D. Hutto and E. Myin. Notre Dame philosophical reviews. http://ndpr.nd.edu/news/40035-radicalizing-enactivism-basicminds-without-content/. Accessed: 04/06/2018.

  58. Robins, S. (2016). Misremembering. Philosophical Psychology, 29(3), 432–447.

    Google Scholar 

  59. Robins, S. (2016). Representing the past: Memory traces and the causal theory of memory. Philosophical Studies, 173(11), 2993–3013.

    Google Scholar 

  60. Robins, S. (2017). Memory traces. In S. Bernecker & K. Michaelian (Eds.), The Routledge handbook of philosophy of memory (pp. 76–887). New York: Routledge.

    Google Scholar 

  61. Robins, S. (forthcoming a). Confabulation and constructive memory. Synthese.

  62. Robins, S. K. (forthcoming b). Mnemonic confabulation. Topoi.

  63. Sant’Anna, A. (2018). Mental time travel and the philosophy of memory. Unisinos Journal of Philosophy, 19(1), 52–62.

    Google Scholar 

  64. Sant’Anna, A., & Michaelian, K. (forthcoming). Thinking about events: A pragmatist account of the objects of episodic hypothetical thought. Review of Philosophy and Psychology.

  65. Senor, T. D. (2007). Preserving preservationism: A reply to Lackey. Philosophy and Phenomenological Research, 74(1), 199–208.

    Google Scholar 

  66. Shanton, K., & Goldman, A. (2010). Simulation theory. Wiley Interdisciplinary Reviews: Cognitive Science, 1(4), 527–538.

    Google Scholar 

  67. Shapiro, L. (2014). Review of Radicalizing Enactivism by D. D. Hutto and E. Myin. Mind, 123, 213–220.

    Google Scholar 

  68. Sutton, J. (1998). Philosophy and memory traces: Descartes to connectionism. Cambridge: Cambridge University Press.

    Google Scholar 

  69. Sutton, J. (2010). Exograms and interdisciplinarity: History, the extended mind, and the civilizing process. In R. Menary (Ed.), The extended mind (pp. 189–225). Cambridge: MIT Press.

    Google Scholar 

  70. Sutton, J., & Williamson, K. (2014). Embodied remembering. In L. Shapiro (Ed.), The Routledge handbook of embodied cognition (pp. 315–325). New York: Routledge.

    Google Scholar 

  71. Szpunar, K. K., Spreng, R. N., & Schacter, D. L. (2016). Toward a taxonomy of future thinking. In K. Michaelian, S. B. Klein, K. K. Szpunar (Eds.), Seeing the Future: Theoretical Perspectives on Future-Oriented Mental Time Travel, pages 21–35. Oxford University Press.

  72. Thompson, E. (2007). Mind in life: Biology, phenomenology, and the sciences of mind. Cambridge: Harvard University Press.

    Google Scholar 

  73. Travis, C. (2004). The silence of the senses. Mind, 113(449), 57–94.

    Google Scholar 

  74. Tulving, E. (1972). Episodic and semantic memory. In E. Tulving & W. Donaldson (Eds.), Organization of memory (pp. 381–402). Cambridge: Academic Press.

    Google Scholar 

  75. Tulving, E. (2005). Episodic memory and autonoesis: Uniquely human? In H. S. Terrace & J. Metcalfe (Eds.), The missing link in cognition: Origins of self-reflective consciousness (pp. 3–56). Oxford: Oxford University Press.

    Google Scholar 

  76. Tulving, E. (2007). Are there 256 different kinds of memory? In J. S. Nairne (Ed.), The foundations of remembering: Essays in Honor of Henry L. Roediger III (pp. 39–52). Abingdon on Thames: Psychology Press.

    Google Scholar 

  77. Varela, F., Thompson, E., & Rosch, E. (1991). The embodied mind: Cognitive science and human experience. Cambridge: MIT Press.

    Google Scholar 

  78. Vosgerau, G. (2010). Memory and content. Consciousness and Cognition, 19(3), 838–846.

    Google Scholar 

  79. Werning, M., & Cheng, S. (2017). Taxonomy and unity of memory. In S. Bernecker & K. Michaelian (Eds.), The Routledge Handbook of Philosophy of Memory (pp. 7–20). New York: Routledge.

    Google Scholar 

Download references

Author information

Affiliations

Authors

Corresponding author

Correspondence to Kourken Michaelian.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Thanks for feedback to audiences at the Naturally Evolving Minds conference at the University of Wollongong in February 2018 and the Memory and Perception: Fishing for Connections workshop at the University of Otago in May 2018. Thanks also for written comments to Carl Craver and John Sutton and for extremely interesting reports to two referees.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Michaelian, K., Sant’Anna, A. Memory without content? Radical enactivism and (post)causal theories of memory. Synthese 198, 307–335 (2021). https://doi.org/10.1007/s11229-019-02119-7

Download citation

Keywords

  • Episodic memory
  • Radical enactivism
  • Memory traces
  • Mental content
  • Causal theory of memory
  • Simulation theory of memory