Sweet Dreams are Made of This

Anything is fair game in a psychology class. Teaching psychology has made me learn the subject much better. Now I can anticipate the kind of questions that students have about various topics. Anybody who has taken an intro psych class knows that one of chapters covered is about sleep and dreams. Personally, this is one of my favorite chapters (although I could go all semester just discussing human memory). Anyway, during my first semester teaching, a student made an interesting comment when we got to the chapter on sleep and dreams. I asked the class where dreams come from thinking that we could discuss the material in the textbook. This student replied that his mom told him that dreams come from another dimension. Let’s take a look at what we know about dreams and then I will tell you how I replied to his comment.

Dreams come from another dimension. How could we know if this was true or not? You can’t test it. You can’t disprove it. But how do you know that it’s not the case? Well, one of the telltale signs of pseudoscience is that they are largely unprovable. This is the case with pseudosciences such as astrology and palmistry. A person who endorses astrology will often try to shift the burden of proof onto the skeptic by saying that they need to disprove its existence. For something to be scientific, we need to be able to formulate hypotheses that can disprove its existence. Anything that is unprovable is by definition not science. Science stipulates the conditions by which a theory is true or not. If the theory stands up to scrutiny and investigation then we accept it; if the theory can be falsified then we discard it.

So, what do we know about where dreams come from? Sleep follows a kind of architecture through the night. Typically, people go through stages 1 to 4, then they come back up to stage 2, and then they alternate between stages 2 and REM (rapid eye movement) sleep for the rest of the night. Stages 1 and 2 are the light stages of sleep, while stages 3 and 4 are the stages of deep sleep. Regardless of whether a person says they usually remember their dreams or not, more than 85% of the time they will report a dream if they are awoken during REM sleep. As a result, REM sleep is the stage most often associated with dreaming.

During REM sleep, a structure in the brainstem called the pons emits electrical discharges to different parts of the brain. When the messages are sent to the visual cortex, we see images; messages sent to the areas of the brain responsible for memory have us access memories; messages sent to the emotional part of the brain have us experience feelings; and messages sent to the front part of the brain cause us to try to make a story out of all these experiences. There is much debate about what dreams mean, but what happens physiologically cannot be disputed.

REM sleep appears to be something that is associated with cognitive development. Infants spend up to 50% of sleep in REM, whereas adult spend only 15 to 20% of their sleep time in REM. Animals that need to fend for themselves right from birth have less REM than other animals. The guinea pig, for instance, is a natural prey animal. The only way it can defend itself is to freeze or run. As a consequence, guinea pigs spend only 10% of their sleep in REM. Humans, on the other hand, are basically helpless from birth. We need caregivers to keep us alive. So, in a way, REM sleep is a luxury that certain animals have. Another interesting thing about REM is that it is something that evolved phylogenetically in mammals. Reptiles and amphibians do not experience REM, whereas mammals do.

This brings us back to the original question about whether dreams comes from another dimension. We can’t test whether this idea is true or not. We do know, however, what happens in the brain while we dream. If beings from another dimension were beaming our dreams to us, then they would know only to do it during the last four hours of the night when the pons was actively transmitting electrical messages to different parts of the brain. The aliens might know about the human sleep cycle. They might know when the right time during the night is to send their messages. All the evidence points to dreaming being a natural phenomenon that aids mammals in cognitive development. So, in response to my student’s question, I said that the aliens might be smart enough to know all these things, but it seems very unlikely this is what is happening. Dreams come from another dimension. I don't think so.