Dreaming of Memories
Melanie Rosen (Trent University)
You are driving home on a rainy night. Turning the corner, the tires lose their grip on the wet surface and your car spins towards a power pole. Struggling to gain control, you feel sweat dripping down your back and a sense of helplessness washes over you, just like the first time. You crash into the pole, again, but fortunately for you, instead of living through the consequences of the crash for a second time, you wake up.
What just happened?
After experiencing a traumatic event, this memory can be ‘replayed’ in a dream. Reportedly, such ‘replay dreams’ can be just like the initial experience. Sometimes individuals report that in the dream, they have relived the event for a second time. It is as if they were hallucinating, embedded in a virtual reality in which, from the first-person perspective, they were back in the same traumatic event. It is also possible—although not common—to have replay dreams of experiences where no trauma is involved, for instance, being back at last week’s party.
Should we class these replay dreams as remembering?
Whether we should call mental states that appear to replay events in sleep as type of ‘remembering’ depends on what memories are. If memories are simply experiences that are stored in the brain and then replayed—either intentionally or unintentionally, when a recalled event ‘pops’ into your head—then dreams that replay memories could certainly be considered ‘remembering’. The question then is simply whether these kinds of dreams really occur. Of course, many people with post-traumatic stress disorder (PTSD) report replaying events and some people who have not undergone trauma occasionally report the same. We can then ask, firstly, do dreams really replay our experiences, and secondly, if they do, should we call these experiences remembering?
In his research on dreams and PTSD, Hartman (2010), found that dreams are never exact replayings of the traumatising event. This might, at first glance, suggest that dreams do not replay experiences. In Hartman’s view, there are always one or more changes between the dream and the memory of the inciting event. For instance, many of these reports come from people who experience PTSD after war. Hartmann gives the example of a dream which replayed a traumatic memory of being in a foxhole with shells exploding nearby. While the subject insists that it was just like his original experience, on closer inspection, this dream could not have been exactly what happened. The dreamer dies in the end due to being too close to an exploding shell, which clearly did not occur in real life as the dreamer lived to tell the tale.
We might say, then, that a replay dream simply draws upon the memories of the dreamer which are used as material to compose the experience. Dreams often or perhaps always draw on memories, even when they are not ‘replayings’. However, it would be an unfair assessment to lump regular dreams with replay dreams as they have important differences. In ‘quotidian dreams’, the dream draws on memory and knowledge rather than replaying experiences. A common dream is that you are back in your childhood home, as you remember it, but you are your current age and the events that occur are not ones that you have experienced before. Replay dreams may have one or more changes from the original experience whereas quotidian dreams draw on elements of memory in the production process in a different way. How should we distinguish between drawing from and replaying memory? The foxhole dream was accurate up until the end, where it diverges significantly from reality – is this difference enough to not be considered a replay? To elucidate this difference, it will be helpful to make a few other distinctions, drawn from the literature on memory.
The process of recalling a memory, is now accepted amongst researchers as a process of creation, not simply replay (for instance, see Sutton, 1998). In fact, every instance of replay might alter the memory that is stored in the brain, known as a memory trace or engram. Thus, if we are to reject replay dreams as a type of recall, it should not simply be because they are not exact replayings of the original experience.
If we were to claim that remembering must be an exact replaying,
then humans may not be capable of remembering at all.
Thus, Hartmann’s discovery should not lead us to reject replay dreams as recall as that would hold replay dreams to higher standards than normal recollection.
Quotidian dreams draw on memories rather than replay them. When I dream of a beach scene, my representation of a beach draws from my memory of what beaches look like, and this might be the case for nearly all dream elements. “Continuity theorists” of dreaming argue that dreams reflect waking experiences, thoughts, and concerns (Hobson & Schredl, 2011). However, representing my friend’s face accurately in an imagined event is a different kind of mental state than recall, such as recalling my friend’s birthday party. Replay dreams also seem to be a different mental state than quotidian dreams. However, there are differences between dreaming and normal recall to consider before considering some dreams to be recall.
Replay dreams differ from waking recall in that they are not experienced in the same way. Dreaming does not have the same phenomenal feel as waking recall. We almost always think that we are awake in dreams. Dreamers report feeling a virtual embeddedness and embodiment within the dream, we feel that we are inside the dream world and our dream body can interact with this world (for a review of this description, see Rosen, 2024). We do not usually experience this during normal waking recall, and we should be very glad that remembering does not immerse us into a virtual world of the past! We might describe remembering as more like imagining in terms of the mode of presentation. A remembered landscape ‘looks like’ an imagined landscape, although there might be some other phenomenal differences between imagining and remembering, such as the sense that the remembered scene did exist (Rosen & Barkasi, 2021). Should mode of presentation make us reject replay dreams as a type of recall? Alternatively, perhaps recall does not usually involve intense hallucination, but that is not sufficient to exclude the potential for hallucination to be a type of recall.
Another reason to reject replay dreams as memories is that they play a different role in cognition than normal recall. Memory gives us access to the past—whether in an entirely reliable way or not. Remembering is an essential aspect of cognition without which our lives would be entirely different. Recall can be spontaneous or intentional and we constantly draw on it. Replay dreams are only spontaneous, although it is conceivable that while lucid, one could bring about intentional replay of a waking experience. Lucid dreams are dreams in which we realise we are dreaming and sometimes have increased control over the dream scene (LaBerge, 1981). These dreams are, however, very rare, and non-lucid dreams do not allow us to access past events the same way normal remembering does. In fact, since dreamers do not usually realise they are dreaming, they may also not realise when they are re-experiencing an event. Moreover, the fact that replay dreams are also rare except in people who have PTSD suggests that these dreams might serve some specific trauma-response function, or have some causal relation to trauma. The fact that such dreams do not serve a memory-like function seems a better reason to reject them as recall than mode of presentation.
A further puzzle that arises for replay dreams is our recall of these dreams after we wake up. Let’s say I have the aforementioned car crash replay dream and then remember it the following morning. If replay dreams are a kind of recall, what do we say of the recall of the dream that occurs upon waking? Is it another instance of recall, as occurs with waking recall, or is this a recall of a new experience? While it can be argued that every instance of recall changes the engram such that every instance of remembering after the first is a recall of a recall, ‘replay dream recall’ seems to have a distinct sense of recalling a new event even if we describe the dream as replaying the event.
Perhaps replay dreams should be seen as a kind of virtual simulation that draws on memory much more closely than normal dreaming, which, more often than not, is brought about by trauma. Thus, these dreams are not themselves a type of recall. This conclusion comes from taking into consideration mainly how replay dreams function in our mental life compared to the function of normal recall.
Hartmann, E. (2010). Dream Is a Creation, Not a Replay. A Dream Always Makes New Connections, Guided by Emotion. In The Nature and Functions of Dreaming (pp. 23-30): Oxford University Press.
Hobson, J. A., & Schredl, M. (2011). The continuity and discontinuity between waking and dreaming: a dialogue between Michael Schredl and Allan Hobson concerning the adequacy and completeness of these notions. International Journal of Dream Research, 4 (1), 3-7.
LaBerge, S. (1981). Lucid dreaming: Directing the action as it happens. Psychology Today, 15(1), 48-57.
Rosen, M. G. (2024). The Dreaming Mind: Understanding Consciousness During Sleep: Taylor & Francis.
Rosen, M. G., & Barkasi, M. (2021). What makes a mental state feel like a memory: feelings of pastness and presence. Estudios de Filosofía(64), 95-122.
Sutton, J. (1998). Philosophy and memory traces: Descartes to connectionism: Cambridge University Press.