Self-Referential Memory and Mental Time Travel

Abstract

Episodic memory has a distinctive phenomenology. One way to capture what is distinctive about it is by using the notion of mental time travel: When we remember some fact episodically, we mentally travel to the moment at which we experienced it in the past. This way of distinguishing episodic memory from semantic memory calls for an explanation of what the experience of mental time travel is. In this paper, I suggest that a certain view about the content of memories can shed some light on the experience of mental time travel. This is the view that, when a subject remembers some fact episodically, their memory represents itself as coming from a perception of that fact. I propose that the experience of mental time travel in memory is the experience of representing one of the elements in this complex content, namely, the past perceptual experience of the remembered fact. In defence of this proposal, I offer two considerations. Firstly, the proposal is consistent with the idea that memories enjoy a temporal phenomenology (specifically, a feeling of pastness). Secondly, the proposal is consistent with the possibility that some of our other cognitive capacities might yield an experience of mental time travel which can be oriented towards the future. I argue that the received conception of mental time travel is in tension with those two ideas.

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Notes

  1. 1.

    In this discussion, I will focus on memories that we report as being about facts, as opposed to objects, properties or events. Thus, I will focus on the kind of memory that we would express by saying, for example, ‘I remember that Mary was a the party’, and not on the kinds of memories that we would express by saying ‘I remember Mary’, ‘I remember being at the party’ or ‘I remember the party’. The reason for concentrating on this type of memory is that this is the type of memory that we express propositionally. However, the account of episodic memory to be proposed below generalises to non-propositional memories; memories that we report as being about objects, properties and events. (See note 20.)

  2. 2.

    The terminology originates in Endel Tulving’s (1972). One may have episodic memories of facts which, unlike the presence of the house keys on the kitchen island, are not objective. Thus, one may episodically remember one’s past moods, or one’s past dreams. For the purposes of this discussion, I will concentrate on the simpler case of episodic memory for facts that one perceptually experienced in the past.

  3. 3.

    If cognitive operations, in general, have an associated phenomenology, then this seems quite plausible. On cognitive phenomenology, see (Bayne and Montague 2011).

  4. 4.

    Tulving, for example, distinguishes episodic memory from semantic memory by appealing to this aspect of episodic memory in (2005, 9). His definition of episodic memory in (1983, 1) also mentions ‘travelling back into the past in one’s mind’.

  5. 5.

    The converse is not true. A subject may perceptually experience a fact, and tell a friend what their experience was like. Later, the subject may forget what it was like for them to experience the fact in the past. But they may learn, through their friend’s testimony, what it was like for them to experience it. In that case, the subject is in a position to form beliefs about their past experience of the fact without remembering the fact episodically.

  6. 6.

    An anonymous referee contends that there could be ways in which the state of remembering might represents a past experience which do not involve the rememberer knowing what the experience was like. While I agree that there are such states of remembering, I do not think that we would be inclined to classify them as episodic rememberings.

  7. 7.

    In (2005, 14). The idea that a subject who remembers a fact episodically ‘relives’ the remembered fact can be found throughout Tulving’s work. See, for example, (2001, 21), (2002a, 6), (2002b, 313) and (1983, 1).

  8. 8.

    Let us not underestimate this virtue of the view, since it is not easy to achieve. It is tempting, for example, to try to explain the intuition that there is a certain type of mental projection in memory by appealing to the idea that memory involves a special kind of consciousness. If one follows that path, one is trading the mystery of what mental time travel is for the mystery of what that type of consciousness amounts to. And, on the face of it, solving the latter mystery does not seem to be an easier task than solving the former one.

  9. 9.

    The feeling of pastness in memory is discussed, for example, in (Russell 1921, 161–162), (James 1890), and (Bergson 1911).

  10. 10.

    For this objection, see (Matthen 2010, 8) and (Byrne 2010, 21).

  11. 11.

    Some empirical reasons for thinking that the feeling of pastness is not essential to episodic memory can be found, for example, in (Michaelian 2016, 117). The feeling of pastness in memory is also downplayed in (Teroni 2017) and (Debus 2016).

  12. 12.

    For reasons discussed in (Fernández 2019).

  13. 13.

    Naturally, if I expected to hear the final note, then one of my mental states has not been fulfilled, namely, my expectation. But my expectation is different from my imaginative episode of the relevant auditory experience. My expectation is identical with (or at least partly composed of) my belief that I was going to have the experience in question. And it is this belief, and not my imaginative episode, which has turned out to be false.

  14. 14.

    Strictly speaking, it is false that there is no such thing. But it seems that the only scenario in which such a thing could happen is a time travel scenario. Thus, in order to allow for the possibility of mental time travel to the future in cases of intended experience, the advocate of the re-presentation view needs to claim that all cases of intended experience are, in fact, instances of time travel. This claim is intelligible, but it is also highly implausible.

  15. 15.

    There is a complication worth highlighting here. There are two senses in which an intentional state can be accurate, or true, ‘with respect to’ a possible situation. It can be true in that situation, or it can be true of that situation. Consider my belief, in the actual situation, that nobody believes anything. Consider, furthermore, a different possible situation in which nobody believes anything. My belief is true of that possible situation, but it is not true in that possible situation. Hereafter, when I talk about a memory being accurate, or true, with respect to a possible situation, I will mean that the memory is true of that possible situation. For more on this distinction, see (Adams 1974) and (Pollock 1985).

  16. 16.

    Notice that, since I will be working with a notion of content according to which the contents of memories are identical with their accuracy conditions, the sense in which the causal histories of our memories are part of their contents is that their accuracy conditions involve those histories. There is a narrower conception of mnemonic content according to which the properties represented by our memories must be properties which can be imagistically represented. Mohan Matthen, for example, makes this claim on the grounds that episodic memories are inherently imagistic in (Matthen 2010). This conception of mnemonic content is narrower than that which I will be working with because, as far as I can see, every property imagistically represented by a subject’s episodic memory will need to have been instantiated for the memory to qualify as being accurate, but the converse is not true. For example, in order for the memory to be accurate, the remembered fact will need to have been perceptually experienced by the subject of the memory. But the fact that it was them, and not someone else, who perceptually experienced the remembered fact, is not something which is imagistically represented by the subject’s memory. Similarly, in order for the memory to be accurate, the subject’s memory will need to causally originate in that perceptual experience of the subject. But the fact that it was that perceptual experience, and not testimony or imagination, which has given rise to the memory is not something which is imagistically represented by the subject’s memory either.

  17. 17.

    In (1983, 85).

  18. 18.

    In (2001, 228).

  19. 19.

    Nothing in the view proposed below hinges on the fact that P is a perceptual experience of an objective fact. The proposal applies to the case in which M is a memory which originates in a dream, a mood, or some other mental state which does not involve our awareness of an objective fact.

  20. 20.

    Notice that the reflexive view can be extended to memories that we report as being, not about facts, but about objects, properties or events. In those cases, the proposal is that a memory represents itself as causally originating in a veridical experience of some object, property or event. (See note 1.)

  21. 21.

    What about the extreme case in which M is a ‘false memory’, that is, a mental state which falsely appears to me to be a memory? The reflexive view of mnemonic content allows for the possibility that mental states other than memories, and in particular so-called false memories, have contents with the CSR structure, just like genuine memories do. In fact, if the phenomenology of episodic memories is, as I will argue below, due to the nature of their contents, then this is precisely what we should expect. For false memories are often mistaken for genuine memories due to the fact that they enjoy a similar phenomenology.

  22. 22.

    Denis Perrin argues against the idea that the feeling of pastness in episodic memory stems from a representation of the causal origin of the memory in (Perrin 2018, 45). According to Perrin, if pastness derives from the representation of causality in the memory, then the feeling of pastness would be concluded or derived from the representation of causality. And this, Perrin argues, conflicts with the fact that the feeling of pastness is an intrinsic part of the phenomenology of episodic memory. I agree with Perrin that a subject does not have the feeling that a fact they are remembering took place in the past because they are inferring this piece of information from the content of their memory. But this does not mean that the feeling does not arise from the representation of the causal history of their memory. What happens to the subject, when they have a feeling of pastness associated with their memory, is that they experience one of the things represented by their memory. We commonly have perceptual experiences with associated phenomenal features when those experiences represent certain properties. By looking at a blue wall, for example, I experience the fact that my perceptual state represents a certain reflectance property of the surface that I am looking at. I experience it in a qualitiatively distinctive way; the way which is characteristic of seeing blue. The thought is that, analogously, by remembering the red apple, I am experiencing the fact that my memory represents its own causal history in a distincitive way which involves the feeling of pastness. The feeling of pastness is not inferred from the representation of the causal history of my memory, just like the experience of colour blue is not inferred from the representation of the relevant reflectance property.

  23. 23.

    A similar idea can be found in (Soteriou 2018, 307–308). Soteriou seems to accept that the experience of mental time travel, when we have a memory, is due to the fact that the memory represents the past experience in which it originates. A difference with the account proposed here is that Soteriou does not try to account for the feeling of pastness in memory by appealing to the structure of mnemonic content.

  24. 24.

    For a discussion of the nature of mental representation broadly, see (Stich 1994). For an overview of the issues on representation and cognition more specifically, see (Ryder 2009).

  25. 25.

    See (Searle 1983) for a defence of this idea.

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Fernández, J. Self-Referential Memory and Mental Time Travel. Rev.Phil.Psych. 11, 283–300 (2020). https://doi.org/10.1007/s13164-019-00453-w

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