On Dreaming

What is the function of dreaming? To answer this “we then need to ask ‘what is the function of waking consciousness?’ To answer that question we need to know what waking consciousness is doing”. Dreaming is the most often occurring altered states of consciousness, yet its function remains unsolved. In this exclusive interview, Katja Valli discusses her research and work into the content, neural correlates and function of dreaming.


Katja Valli

Katja Valli

Richard Bright:  Can we begin by you saying something about your background?

Katja Valli: I trained in psychology and, very early on, when doing my Masters, I was already very interested in evolutionary biology, and studied it independently. In our psychology training, evolution was not mentioned, even once. It was also the same with sleep, I think we had only one forty five minute lecture on sleep. Sleep was an area that intrigued me and when it became time for me to choose a topic for my Masters I ran into Professor Antti Revonsuo, who was also interested in dreaming and evolution. I did my Masters on the biological function of dreams in 1999 and my Phd on the same topic in 2008. So, my background training in psychology indirectly linked to this interest in evolutionary biology, psychology, sleep and dreaming. All those combined, and twenty years later I’m still working on sleep, dreams, and evolutionary psychology.

RB: Your research focusses on sleep and dreaming. What function does dreaming serve?

KV: This is a tricky question, because we don’t know. We don’t even know whether it serves any function at all. Similarly, the function of sleep remains a mystery. When we study sleep we always ask ‘What is the function of sleep?’ instead of asking the question ‘What is the function of waking consciousness?’ We are actually doing the same thing with dreaming, we are asking ‘What is the function of dreaming’ instead of asking ‘What is the function of having experiences during wakefulness?’

My take on the issue is, awake and sleep, and waking consciousness and dreaming consciousness, shouldn’t be studied separately, but they are two sides of the same coin. If the waking consciousness has a function, and very few doubt it has, then I think that what the dream consciousness does is either reflect this function, or if dreaming has some sort of additional function then it must be very closely related to the wider function of waking consciousness. So, maybe dreaming is just the side effect of having experiences while awake, and we keep on having experiences while asleep because we can’t shut down the brain while asleep. I think we still have to take into account the possibility that, even if dreaming originally acted as a side effect of waking consciousness while asleep, then maybe later dreaming became productive for another use, so that dreaming itself started to serve a biological function or an evolutionary function. But as to the question of what function dreaming serves, the jury is still out and I can’t even guarantee that it has a function at all, that is, an independent function that it will do something that waking consciousness doesn’t do, or that sleep doesn’t do.

RB: As you say, it’s not an independent function of waking consciousness, it’s a continuation of.

KV: I think that the problem is that the question has always been framed as ‘does dreaming have a unique function?’, and then different types of functions have been suggested, but every time I look at these theories I ask, ‘what do these add to the waking state, how well can the brain do these during wakefulness?’ If we think in terms of natural selection, and in terms of survival and reproduction functions, selection operates during wakefulness. Sleep in itself is a state that puts the organism into a vulnerable position, so sleep has to add something to waking functions that is so valuable that sleep was favoured. I think that the same could then apply to dreaming as well, that it could add something to the waking function. It could help someone perform better, or remember better, or function better than during waking hours, because that is when the selection occurs. But I don’t think dreaming does anything unique that the waking consciousness does not do at all. Rather, resources are allocated differently during dreaming and waking, and dreaming only adds to the effectivity of functions that also take place during wakefulness. Another option is that dreaming has no function. Maybe it simply reflects what the brain does during wakefulness and then it does the same things during sleep. Conscious experiences cannot be completely turned off during sleep.

RB: What is the definition of an altered state of consciousness and what kind of states are there?


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