"What are Dreams?", by Will Johnson, firstname.lastname@example.org on knol.google.com
Creative Commons Attribution 3.0 License
What are dreams? Why do we have them? Do lower forms of life have them as well? How low?
I present a theory of my own.
Our brains are not a single coherent entity, but rather many separate functions all running simultaneously and presenting information to each other on occasions and keeping other information suppressed as well.
During the time we're awake, we have both sensory and low-level internal inputs, constantly being processed by mid-level systems. All of our sensory input cannot rise to our consciousness, as we would be overwhelmed with information about how soft the chair is, how the coffee smells, whether we're warm or cold and so on. The vast majority of these inputs are shut out by a system which determines what might be important and what is not. The important information is presented to our consciousness so we can act on it, while the unimportant information is not presented to our consciousness at all.
These sensations are not completely ignored however by other processes. Within our brain we have a process that I call the Story Teller. The Story Teller's function is to provide sub-conscious continuity, between our sensations of the world and our concepts about it. That is, when we have the sensation of being warm, the Story Teller incorporates an idea that it's a warm day, the sun is out, the heater is on, and so on. It turns the sensation into some kind of meaningful higher-level concept. Once the importance of that higher-level concept rises to our consciousness, we are presented not only with the idea that we feel warm, but also with the idea that the sun is shining into the room and we should open a window, or the heater is on and needs to be turned down. The Story Teller has woven several external and internal strands into a consistent continuous concept about our situation and presented it intact to our conscious brain to act upon. The continuous sensations then sink again to the mid-conscious level.
However, in addition to the Story Teller being able to present to our consciousness, our consciousness also exerts a counter-force against the Story Teller. The Story Teller can apparently make conceptual mistakes, turning "I feel warm" into "there is a fire on my skin" and so on. So there is a dampening function also at work, we'll call him the Skeptic. The function of the Skeptic is to decide whether something the Story Teller has come up with, seems likely or not. The Skeptic might compare the story to memories of other situation, or logical outcomes, and decide to silence the story or alter it by dampening the most outrageous parts of it.
When we go to sleep, our highest conscious brain shuts off, and the Skeptic shuts off with it, in addition the majority of the low-level sensory processors shut off. Our Story Teller however, keeps running. The Story Teller now becomes the highest awareness and also in part the lowest, since that part of the brain that had kept it in check, is asleep, and as well the majority of sensory input is shut off. Now there is nothing to stop the Story Teller from weaving whatever story it can think of, and since there is little sensory input to act upon, it creates these stories mostly from various concepts and memories stored in the brain. With little sensory input for it to match up to, it generates instead seemingly random requests to memory and then tries to create a consistent story out of the results it receives. So the "consistent" stories it creates can become quite outrageous.
The Story Teller's stories do not represent repressed ideas, nor memories of the day, nor prophetic dreams. Dreams can sometimes be manipulated by focusing the brain on a certain concept while you are going to sleep. This "primes" the memory to present that concept in-focus for the Story Teller to grab. Other memories and concept it grabs with that however can still be rather random. So your dead mother might want to talk to you how peanut butter can save life on Mars. That's what causes dreams.
Life forms with an internal Story Teller can dream. So dogs dreams, cats dreams, possibly all mammals dream. However animals that do not require continuity, do not have a Story Teller, and so do not dream.