Thinking about thinking is hard, and thinking about dreaming is harder. Believe it or not, there is only one evolutionary theory of dreaming seriously at work these days in academia. Indeed, a theory supporting the biological function of dreams has a steep hill to climb, as we don’t really have a complete theory for the biological function of sleep. So dreaming is still an unknown within an unknown.
But that hasn’t stopped Antti Revonsuo, a Finnish philosopher who teaches at the University of Turku. At the 2008 IASD conference last month, researcher Katja Valli discussed the newest findings of the Revonsuo’s team in regards to their Threat Simulation Theory for dreams.
In a nutshell, the theory states that the biological function of dreaming is to stimulate threatening events in order to rehearse the perception of threats and how to go about avoiding them. So our ancestors are those who were good dreamers, and used dreams to practice the mental and physical skills needed to survive in the world. What isn’t stated in this theory is whether or not dreams need to be remembered for them to do the job. Perhaps dreaming the tiger and forgetting about it did the trick?
This theory rests on the widely-accepted observations that most remembered dreams are stressful – filled with negative emotions and dramatic conflicts. Revonsuo focuses on this empirical dream content, and has spent the last decade illustrating the patterns of threats in the dreams of children, traumatized patients, nightmare sufferers, and even some contemporary hunter-gatherers for cross-cultural comparison.
Most recently, Revonsuo, Katja Valli and their team (see citation below) have focused on the threatening images of children – comparing traumatized children versus non-traumatized. They found that traumatized children (from war, abuse, and natural disasters) do indeed have more threats in their dreams. It’s as if their early life triggered the dream simulation into high-gear.
Anyhow, many clinical psychologists would agree that dreams are revealing of our central conflicts, our past traumas, and so they represent a way of working with the turmoil of living. What marks this as an evolutionary theory, however, is tying this folk wisdom (and I mean this with all respect – this is empiricism at the ground level) to the evolutionary goals of reproductive success and the passing on of ones genes.
I”d love to hear some psychologists and anthropologists comment on this paring!
For me, this theory is intriguing, but it does not account for a mechanism that clearly links “successful dreaming cognition” with reproductive success. I”m not a strict materialist either, but if you”re going to play that game, you gotta stay within the rules. If we”re just ticking meat sacks, then we need mechanisms.
Deeper still, this theory rests on the assumption that early human life was full of risks and trauma that are not present today – the old “tiger in the woods,” red tooth and nail. Reminds me of the Footprints of Acahualinca, which I saw in Nicaragua a couple years ago. For many years these amazing “fossilized” human footprints from 6000 years ago were thought to show a tribe of humans fleeing from a volcano. That has been recently disproved, based on improved geological information and dating techniques
But look at the gait of those footprints – this is a group of people sauntering across the mudflats, not running for their lives. It’s so easy to project “disaster and terror” onto the distant past, but truthfully there is more danger in the world now than ever before. Tigers still eat solitary humans, but today’s real dangers are much bigger and systemic: overpopulation, mass extinction rates, peak oil, GM foods, and the techno-military wing of global capitalism that threatens all of us.
My point is: life is still hard, and life is still beautiful. Dreaming as threat stimulation is only the first slice of the function of dreams being currently debated in the West. Ultimately, the theory a great first step, but it denies the rich imaginal levels of dreams that are just as important for human meaning: which is what people really talked about around the campfire a hundred thousand years ago.
VALLI, K., REVONSUO, A., PALKAS, O., ISMAIL, K., ALI, K., PUNAMAKI, R. (2005). The threat simulation theory of the evolutionary function of dreaming: Evidence from dreams of traumatized children. Consciousness and Cognition, 14(1), 188-218. DOI: 10.1016/S1053-8100(03)00019-9
Hi Ryan,
Great article. I’m really enjoying your posts about the presentations and discussions from the IASD conference. It makes me wish I’d attended!
This theory about dreaming as threat simulation is intriguing, at least as an explanation for the origins of dreaming. It doesn’t seem to explain why so many dreams feature aspects lifted from memories of events that have already taken place, except perhaps as a mechanism of incorporating real-life details to create a more realistic scenario for practice at surviving similar situations.
How does this theory explain common dream themes that seem to have no relation (metaphorically or otherwise) to threats? For example, I can understand how in our modern world the fear of being unprepared for a situation could prompt stressful dreams about finding yourself in a classroom and being unprepared for the exam. That could be considered a threat simulation because in certain situations being unprepared could translate into a threat to your survival. On the other hand, how do we translate a dream of teeth falling out? What sort of threat simulation is being represented in that dream?
I’ve never had a dream of being unprepared in a classroom or of showing up naked at school or at work, and I’ve never encountered anyone who has had those supposedly common dreams, but I’ve encountered several people who have dreamed of losing some or all of their teeth and I once had that type of dream myself. I wonder if it is a theme carried forward from our ancestors and somehow translates to the threats of starvation, famine, tainted food, etc.
Teeth and words/speech share the location of the mouth. Words fall from our mouths. If the words are rotten (gossip etc), the person might dream of rotten teeth falling from their mouth. Usually this comes the night after uttering “bad” words the previous day.
I like the way you frame this theory as one layer of advantage for dreaming consciousness, without reducing its purpose to only threat stimulation practice.
I have to be careful with these theories. Evolutionary biology is like candy to me – irresistible, but full of empty epistimological calories, because we have so much trouble seeing outside our projections of the past. However, it seems safe to say that psychological, cultural, and biological phenomenon that do not help in some way don’t stick around very long.
I wonder about the practice aspect of the theory, since many of the responses I’ve had to dream threats are not plausible reactions in reality, such as melting through a floor, or leaping off a building. Perhaps the practice is not about how you respond, but to help keep you from freezing when you meet a form of terror.
Do you know if these researchers are bracketing dreams as a human-only experience?
Yikes, I meant Evolutionary Psychology (not biology) is candy…that’ll teach me to respond while I’m sleepy.
I couldn’t agree more with your assessment, dreams as threat practice is only one piece of the pie. This theory wouldn’t account for why humans must dream, for hasn’t been proven that if we don’t dream after a certain period of time our mental processes suffer? IMO that seems to point to a deeper attachment between dreaming and consciousness.
thanks for the feedback, ya’ll. sorry I’m so late to the game – I took off this weekend for a backpacking trip in the wilds of the CA mountains.
so, Kris: I think Valli and Revonsuo would respond by suggesting that many of today’s threats are not the ones we’ve been “hardwired” for in the last few hundred thousand years – on the other hand, the classroom dream is a form of social stress/embarrassment and that’s variable but definitely old-school. I spoke to Valli about this point and she suggested that basically “the modern era is not adaptive” ie. there are many novel threats that may not trigger threat simulation or vice versa, insignificant threats may trigger the simulation.
dreams of teeth: now that’s old-school! They are literally the greatest source of our mortality and definitely constitute a threat/indicator of health. Modern dentistry has shielded most of the first world from that ugly truth, but in the old days, and in many parts of the world today, an infected abscessed tooth can be deadly. (side note: out teeth were healthier before we adopted the grain diet of the neolithic, 6000 years ago).
so, based on their research, if you live a tough life (early exposure to trauma, personal or systematic), there are more likely to be perceivable threats in the dream. I suppose it’s preparation for the future but also a healing process, if we look to clinical psychology to deepen the theory.
Kathleen – thanks for the compliment and I think you’re on to something that the theory does not address: bizarre (non-rational) responses to dream threats. I melt through walls myself. My attention turns towards the emotional valence in these situations, not the concrete imagery – in other words, gaining courage in traumatic dreams may be helpful for preparing for everyday life’s surprises.
And I’m not sure of Revonsuo’s take on animal dreams (animals dreaming dreams, i mean). Most cognitive researchers are comfortable with dreaming as a proto-mammalian thing at least, given the presence of REM in lower mammals.
of course, dreams do not equal REM. but that’s what we’ve got on the material strata.
Kevin: you’re right about REM deprivation; it’ll mess you up bad, and can lead to native hallucinations (also called REM intrusion) and put you in bodily harm. Eventually you just go to sleep no matter what the stimulus is, iow you pass out cold. There is currently no complete scientific theory that accounts for the need for sleep from a biological perspective. Memory consolidation seems to be the best bet for consciousness-related topics, but all kinds of complex cellular refreshments happen too during sleep.
I agree with you about consciousness and dreams: it’s hand in hand. It’s impossible to discuss the significance of dreaming without nodding to the need to make meaning from these experiences.
If I may be so bold, I think Revonsuo and his team missed the mark. I think that any theory as to why humanity and other species dream must have a basis in brain evolution. When we examine the neurological components of sleep and dreaming, we find that each component evolved in stages that conform to how the brain likely evolved.
According to my study of the available research, dreaming began at the diencephalic stage of brain evolution. Interestingly, the muscle immobility (atonia) that accompany dream sleep evolved in the brain millions of years before it began to dream. The desynchronous brain activity associated with consciousness and dreaming evolved as the brain became capable of processing visual sensory.
The contemporary brain begins to dream at the onset of atonia. My study suggests that atonia evolved as a means to extend the energy reserves of resting animals through periods or cycles of food privation. This process allowed these primitive animals to devote more of their energy reserves to physiological systems more vital to their survival such as heart, lung, and brain.
Resting animals had no need for muscle toncity or readiness during extend periods of food privation. However, they did have need to remain alert to the restoration of food sources.
Dreaming, as my study suggests, is a consequence of the sensory vigilance primitive animals required to remain alert to restored food sources. These early animals didn’t actually dream; they just had actively alert brains of the kind that gave rise to the dreaming brain. This is suggested in contemporary animals through functional study of decortication. Functional study of the normal dreaming brain suggests that dreaming is a type of consciousness or wakefulness rather than sleep.
Evolution of the brain suggests even more about why we remain mostly immobile while our eyes move rapidly when we dream. Our eyes move because their muscle evolved in the brain after those that control muscle tone in the body; our eye evolve with the dreaming dreaming. There is even more to be said as to why dreams are difficult to remember without practice. Evolution of the brain, my friend, is the key.
DreamDoc, thanks for this important perspective. I believe that Revonsou’s perspective can be entertained simultaneously with this lesson in early mammalian sleep function – IF we make the concession that Revonsou’s theory really explores the psycho-biological function of dreams as opposed to the biological origins of dreaming. Two different time-tables here, in my opinion, and both have their own validity.
But I doubt Revonsou would share my opinion. His assumption is that threat simulation pushes back into early mammalian cognition, but he does not actually posit a biological strata or mechanism for such a cognitive leap. This discussion highlights how important it is for some to find biological functions for dreams, in a way so dreaming can be blessed by the white coats of science, today’s shaman-priests and holders of knowledge. Dreaming is looking for legitimization by the sciences and so it often adopts its language – much like anthropology as a field of study, and psychology as well. There was a time, a hundred years ago, that biology sought this legitimization from the ivory tower as well.
The secret moral dilemma underneath this struggle is this question: Is dreaming simply a psychological “after-effect” of a deep biological process – and therefore, is it really valuable? This is a mirror of the larger debate in consciousness studies: is consciousness a thing in itself, or is it an epi-phenomenon?
I think the perspective of dreaming as a “psychological ‘after-effect’ of a deep biological process??? may have empirical support in how the various neurological constituents of dreaming appear to have evolved. When we examine the activity in the brain and brainstem that appears to initiate and constitute dreaming, we find that the separate neurological components of that activity arises in a separate and distinct order that conforms to how the brain evolved.
In the normal brain, dreaming appears to initiate at the onset of atonia. Atonia, as Sir Charles Sherrington discovered and Dr. Michel Jouvet later confirmed, is mediated by neural activity in the metencephalic region of the brainstem. Spinal cord aside, the brainstem is the most primitive component of our central nervous system (CNS) and the evolutional evidence I???ve studied suggests that atonia evolved as an effective means to extend resting animals??? tolerance of prolonged periods without the availability of life sustaining nutrients. In preexistent animals, as in contemporary species, atonia results in the suspension of muscle tone (muscle readiness) and the devotion of energy reserves to neurological and biological systems more vital to survival. At the onset of atonia in contemporary animals, increased heart, lung and brain activity results in more energy usage by these organs.
If we accept the preexistence of animals with metencephalic neural functions (inclusive of atonia) before those with the neural activity and grey matter structures associated with the contemporary dreaming brain, then the activity in the brainstem (atonia) that is perceived as the initiate of dreaming in contemporary animals paints an evolutional portrait of dreaming as an ???after-effect??? of what began as a neural function to sustain life through privation periods.
As to the question of dreaming???s value, I cannot find a single studied that suggests the benefits of dreaming without atonia; however, atonia without dreaming appears to offer benefits equal to normal dream sleep. Rather than dreaming, the evidence appears to promote the value of atonia to beneficial sleep. So the question remains: what is the function of dreaming?
The uptake of energy by the primitive neural components of the contemporary brain at the onset of atonia stimulates neural activity, which activates brain function to almost wakeful levels. The distinction between this type of wakefulness (dreaming) and true wakefulness (consciousness) is the partial cessation of somatosensory afference: the dreaming brain???s connection to physical sensory and reality is partially severed.
When we dream, physical sensory data does not enter our wakeful brain activity as it does when we are consciously awake. Without this data, the dreaming brain???s ability to distinguish physical experience and reality is impaired. When we awake from a dream, we are able to distinguish our experiences within as a dream from true physical reality because of the physical sensory data that rushes into our conscious brain from its reactivated and tonic physical sensory array. Whether we are dreaming or consciously awake, there is no evidence suggesting that our brain engages in a function that is distinct from what it was evolved to do.
I think most researchers agree that the evolved function of our brain is to perceive, interpret and response to sensory data. However, the dreaming brain does not appear to be responding to the sensory data that flows from true physical experience. This leads us to question exact what is the dreaming brain perceiving, interpreting and answering.
The decorticate experiments performed by Jouvet and other researchers showed that the cortex does not engage in any activation without a neural link to subcortical structure. This suggests that the dreaming brain may only engage in this activity through the activation or sensory input from subcortical structure. Simply, the dreaming brain appears to be perceiving, interpreting and responding to sensory data generated by brainstem activation in the absence of a connection to true physical inexperience. Specifically, it is my opinion that the dreaming brain is responding to influences that initiate through hypothalamic activation. This appears to place the source of dream content outside those associated with stored memories.
Looking at the evidence brain evolution appears to provide, I???ve formed very firm opinions about the nature of the mind as it might relate to dreaming and consciousness. From the perspective of brain evolution I???ve studied, a mind is the environment of cognitive activity within the brain that arises from brain function. Neurologically, a mind is quantified by the structure in the brain that gives it???s host the capacity to integrate divergence types of sensory data (aural, tactile, visual, olfactory, oral) in a way that allows the host to engage in behaviors independent of instinct. This is the ability to behave proactively rather than reactively. In the human brain, the structure that appears to give us this ability is the thalamus, which happens to be a brainstem structure of striking resemblance to cortical structure with a right and left hemisphere and hemispheric adhesion.
Dream Doc, I’m not sure how this comment slipped past my radar! As always, I enjoy your reasoning. I get where you’re coming from, brains encase minds. But sounds like you are equating dreaming whole-sale with REM atonia. That association is a little looser than previously thought. Also consciousness, in my book, is distinct from wakefulness, hence lucid dreaming.
But I think you nailed it with the statement: “However, the dreaming brain does not appear to be responding to the sensory data that flows from true physical experience. This leads us to question exact what is the dreaming brain perceiving, interpreting and answering.” Indeed! That’s where dream research begin to get interesting.
Lastly, have you seen Tore Nielen’s recent work about the hippocampus and the neocortex switch hitting with activity during the memory consolidation process? He’s got some interesting data correlated with day residue and memory incorporations from dream reports.
When life began, it was with equal parts of light and dark. the reality explains the whole. When we can explain why we dream we will have the answer to all that makes us what we are and indeed, the destiny that we are designed for.
I’ve been looking for info on dreaming from an evolutionary POV for a while. Most people look at it from the mystic POV and it’s a lot of theory and old wives tales. Great info.
I realize this thread has been “dead” a long time, but I came across it only today. My reason for posting is the OP’s question, “…how do we translate a dream of teeth falling out? What sort of threat simulation is being represented in that dream?”
It’s possible I have an answer to that particular question…not necessarily the only answer, but one I can at least document.
I used to dream constantly my teeth were rotting, turning to mush, or for other reasons falling out…sometimes a single tooth, sometimes all of them.
About 7 years ago, I switched dentists based on a friend’s enthusiastic recommendation. At my first visit, the new dentist noted, among other things, it appeared I had been grinding my teeth frequently. I said I was unaware of it; she replied tooth grinding tended to occur most often during sleep, and unless one’s partner or spouse commented on it, most people remained unaware of it, unless they were familiar with the related symptoms.
She also said a problem with one’s bite was the most usual cause, and went through a common procedure for correcting the problem, i.e., identifying the problem spots using a sort of dental “carbon paper” on which I bit down, then gently grinding down any colored hot spots until no more could be found.
I mentioned this to my partner, who confirmed I often ground my teeth while sleeping. (I omit the brief, mostly amicable, discussion which ensued as to why he had not shared that observation with me previously.)
After a second bite correction a month later, I stopped grinding my teeth at night.
Since then, I haven’t had a single dream in which my teeth – or even a single tooth – rotted, turned to mush, or fell out.
I’m not claiming other people’s tooth-loss dreams invariably incorporate the same “warning” or occur for the identical reason. I only wanted to document my experience, since my own tooth-loss dreams were definitely resulting from night-time tooth-grinding.
If anyone questions that conclusion, I would be interested in hearing their reasons for doing so, so long as their reasons and arguments are logical and have some documented basis in fact. I’d especially also be interested in any scientific studies or publications including similar instances.
For what it’s worth.
All best,
cordwainer
that’s awesome, thanks for sharing. I have bruxism too. I can tell you my teeth dreams definitely come at the more anxious times in my life, and that’s precisely when I tend to grind my teeth in my sleep. I only know bc i wake up with sore jaw. yeah, sometimes health warning dreams are very literal. Here’s another article that explores this idea in greater detail:http://dreamstudies.org/2009/08/05/dreams-come-through-our-bodies/