I’ve had an idea that answers the question “What are dreams for?” floating around in my head for several years now. Whenever there’s an article or a podcast about sleep, I listen to hear whether anyone else has had the same idea. This meaning of life dialog comes close.
Bob Wright asks the classic question “Why do we dream?” and Robert Stickgold gives a long and fascinating answer about the role of dreams in information processing and its relationship to forming memories.
There are studies demonstrating that, if you are given a cognitively complex task to perform and then tested on that task three hours later, your performance will degrade. However, if you have a nap during the three hour interval, you’ll perform even better after the interval than you did when you first attempted it.
A more elaborate version of the study has the researchers waking the subjects from their naps at periodic intervals and asking them what they were dreaming about. The subjects who reported dreaming about the task, performed better at the task when they were retested than those who didn’t. Robert Stickgold’s conclusion is that (one reason) we dream is to help form associations between events. I think this is wrong and it’s got to do with a muddle over the meaning of the word consciousness.
When you wake up in the middle of the dream it seems as if there was consciousness of the dream but if you didn’t wake up, you would never be able to recall it. It’s as though consciousness has to be a part of the information processing infrastructure.
It seems completely obvious to me that memory and awareness are separate functions in the brain and Robert corrects Bob’s error…
You are conflating a couple of things. One has to do with remembering your dreams when you wake up.
…but then goes on to make a similar error himself. Let’s deal with Bob’s error first.
Arguments about the meaning of consciousness have a long and storied history and I expect that a lot of the controversy arises because it’s not obvious what the term consciousness refers to. Is it the difference between being asleep and awake? Is it something to do with recognizing yourself in the mirror? Is it that ineffable quality of experiencing the colour red? I think it’s none of those things and all of the mystery goes away if we stop using the word consciousness and talk about awareness or attention instead.
In a previous dialog with David Chalmers, Bob tried to explain the distinction between perceiving the color red and having the experience of perceiving the color red. That distinction, in a nutshell, according to Bob, is what consciousness is all about and is what separates us from the lower animals and is why machines will never be conscious. But, for the life of me, I struggle to understand this distinction and wonder whether or not I am actually conscious myself.
The real explanation is simpler.
I can perceive the colour red and I can be aware (or not) that I have perceived the colour red and I can have a memory (or not) that I was aware that I have perceived the colour red and those are all separate ideas. It’s well established that we can perceive things without being aware of it—this is the basis for subliminal messaging—but it’s less obvious that we can be aware of something but to then immediately forget that we were aware of it. At least, it’s less obvious to Bob.
When you think about it, our brains must have a finite memory and to make sure we remember the good stuff we have to throw away a lot of the bad stuff and our brains continuously make decisions about which is which. This brings us back to Robert’s explanation of what dreams are for.
Dreams, according to Robert, are for making associations between events and for fitting them into an information schema in our memories so that we can recall them at appropriate times in the future. According to this explanation, our dreams rummage through the day’s events and decide which are significant and which are not (paying special attention to the emotional valence of an event, which is why dreams are often emotionally disturbing). I think this is close, but wrong.
Michael Gazzaniga discovered through experiments on patients with split-brains, that is patients who have had the connection between the left and right halves of their brains severed, that different areas of the brain have different responsibilities. You can think of these areas as specialized modules.
From a New York Times article,
In the decades to follow, brain scientists found that the left brain-right brain split is only the most obvious division of labor; in fact, the brain contains a swarm of specialized modules, each performing a special skill — calculating a distance, parsing a voice tone — and all of them running at the same time, communicating in widely distributed networks, often across hemispheres.
In short, the brain sustains a sense of unity not just in the presence of its left and right co-pilots. It does so amid a cacophony of competing voices, the neural equivalent of open outcry at the Chicago Board of Trade.
In one experiment, Dr. Gazzaniga showed different pictures to different halves of the brain.
The man’s left hemisphere saw a chicken claw; his right saw a snow scene. Afterward, the man chose the most appropriate matches from an array of pictures visible to both hemispheres. He chose a chicken to go with the claw, and a shovel to go with the snow. So far, so good.
But then Dr. Gazzaniga asked him why he chose those items — and struck gold. The man had a ready answer for one choice: The chicken goes with the claw. His left hemisphere had seen the claw, after all. Yet it had not seen the picture of the snow, only the shovel. Looking down at the picture of the shovel, the man said, “And you need a shovel to clean out the chicken shed.”
The left hemisphere was just concocting an explanation, Dr. Gazzaniga said.
In this multi-module model of how the brain works, there is a module for recognizing faces, another for experiencing emotions and yet another for reasoning. But most importantly for our purpose here, there is a module whose job it is to make up stories about what we’ve just seen. Dr Gazzaniga calls it the interpreter or narrator.
The brain’s cacophony of competing voices feels coherent because some module or network somewhere in the left hemisphere is providing a running narration.
Back to the question of what dreams are for. Putting together what we’ve learned from Dr. Gazzaniga and Professor Stickgold, my answer is: nothing at all.
I imagine that there’s a module somewhere in our brain that sorts through our memories, categorizing them and throwing away the useless ones. As this memory sorter looks at each memory, it comes to the attention of the interpreter module which makes up a story about it.
So, imagine your memory sorter going through your recent memories one by one:
- Big presentation at work (file it under anxiety).
- Beautiful lady said ‘Hi’ on the bus (file it under lust).
- Taxes are due next week (file it under dread).
These three things are unrelated except for the fact that they were memories to be filed away. Meanwhile, the poor old interpreter is watching these memories as they scroll by and feels compelled to make up a story about them and suddenly you are back in 10th grade giving a presentation to your class in double history and, when the cute girl in the front row smiles, you realize you are naked and run away screaming.
There’s no rational meaning to the dream (like President Trump, the storyteller’s gonna tell stories whether they are true or not) and if you happen to wake up at the right moment, the story itself becomes a memory. And that’s where dreams come from.
Dreams are not for anything. They are a weird side-effect of your memory-processing system being watched by your story-telling system. They have no function and no predictive power. Just enjoy them.
Dream Photos from Flickr (Creative Commons)