What happens to you when you go to sleep? What happens in your mind? Do you stop thinking, do you simply think less, or do you perhaps just think differently? Do thoughts and emotions in unconscious parts of your mind enter more easily into consciousness? Is sleep somewhat like entering another plane of existence; or perhaps even like death? And why do we spend so much of our lives (approximately a third, on average) sleeping? Does it help us to survive longer? Does it help our minds to run more smoothly? Does it help us to conserve energy or perhaps to create new energy? Can we do with less sleep and still function well? Can we perhaps train ourselves to do without sleep at all?

There are many, many questions we can ask about sleeping and dreaming. How do we begin to answer them? Should we consult spiritualists or others who might have special insight into dreaming? A spiritualist might tell us that dreams are messages from another plane of existence, and that we should pay attention to them since these messages come from entities trying to help us. Should we look at what psychotherapists[∂] have to say about dreaming? A psychotherapist might tell us that dreams are expressions of fundamental concerns that derive from our unconscious minds — concerns about life, death, and the meaning of our existence.

These are extremely interesting claims. You might be wondering how you can be certain that these people know what they are talking about. If we are to be good skeptics, we need to ask the following question: what evidence do these people have for their claims about dreaming? Were these claims simply passed down to them from other authorities? Did they test these claims directly themselves? What would you think if the spiritualist stated that she obtained her information from supernatural entities from an unobservable dimension of reality? Should we trust her evidence? What I am asking you to do is to answer the following question: what would be the best evidence for showing that claims about sleep and dreams are true (or false)?

You've already learned something about the kinds of evidence preferred by scientific researchers. First, scientific researchers are empirical in their approach and, therefore, would want to observe people directly while they slept and ask them about their dreams when they woke up. Second, scientific researchers are skeptical. A person with a skeptical attitude believes that we should always closely examine the evidence supporting any claim and that an answer to a research question is rarely final: new evidence may show that the answer was wrong.

But even if we accept the scientific approach as our starting point, there still is a major problem. What exactly should psychologists observe in order to discover important information about sleep? Should they observe bodily movements during the night; changes in blood pressure and digestion; changes in heart rate; changes in brain activity; changes in what goes on in the mind of a sleeping person? Because there are so many things we could observe, it's difficult to know where to start. It turns out that what we choose to observe depends on what we think might be important proximal or distal causes of the phenomenon we are studying.

In other words, we must already have a theory that specifies some of the causes of whatever it is we're interested in understanding, even if it is a highly speculative theory. For example, if you want to understand why your car isn’t working, what observations are you going to make? It depends on what you believe to be the proximal cause(s) of the normal functioning of cars. If you believe that cars work because of invisible elves living in the glove compartment who, when you turn the key, travel into the engine and make the parts move, then you’ll probably make detailed observations of the glove compartment to see if you can detect any problems with the invisible elves. We know, however, that the normal functioning of a car is caused by the combustion of fuel in your engine that then activates other parts in your engine; therefore, you will make careful observations of the activity of different engine parts. (It still might be that invisible elves do live in your glove compartment, but we don’t have to try to observe them to get the car running again).

In the case of sleep and dreams, researchers most often have observed the following events:

(a) electrical activity of the brain;
(b) bodily movements;
(c) physiological processes;
(d) mental experiences (for example, dreams).

The reasons for observing people while they sleep and asking them what they have experienced during sleep are probably obvious to you — such observations are essential if we are going to understand anything about sleeping and dreaming. The reasons for observing the electrical activity of the brain also should be obvious: as stated in the previous section, electrical activity in the nervous system is the most proximal cause of mental events and behaviors. After deciding what to observe and then making observations, a second problem arises: how should the observations be explained? The development of adequate theories generally is a much greater problem for the scientist than the initial observing and describing of the phenomenon itself. As for sleep, we will see that different theories have been developed depending on what researchers were trying to understand about sleep.

Changes in Brain Activity During Sleep

In order to describe the changes that occur during sleep, two researchers at the University of Chicago — Eugene Aserinky (1921-1998) and Nathaniel Kleitman (1895-1999) — looked at changes in brain waves (Aserinsky & Kleitman, 1953). Before Aserinsky and Kleitman published their first paper in 1953, scientists wishing to describe and understand sleep realized that changes in brain activity must lead to sleep: there were obvious changes in behavior and mental events that could be explained only by supposing that changed electrical activity in the brain was involved. However, not until Aserinsky and Kleitman came along did sleep researchers begin to have a more complete understanding of what these changes were.

What do you think might happen to brain activity during sleep? Since thinking seems to slow down and become more illogical during sleep, it seems reasonable to predict that, the longer we sleep, the less active our brains become, and that our brains become more active only when we begin to wake up again. Before beginning their sleep research, Aserinsky and Kleitman agreed that earlier research had shown this to be true and, therefore, they decided that studying changes in brain activity would be unnecessary and unproductive. But when testing the EEG machine before beginning his research, Aserinsky noticed that, several times during the night, the eyes of the test subject (his eight-year-old son) moved about very rapidly, and that this movement was associated with increased brain activity. In fact, his son's brain became so active that it looked as if he were wide awake! This finding was sufficiently interesting that Aserinsky and Kleitman decided to look at what was happening during these very active sleep periods. They soon referred to these periods as rapid-eye-movement (REM) sleep because of the rapid bursts of eye movements that distinguished it from other periods of sleep.

By measuring changes in brain activity during sleep and determining when particular brain waves were most likely to occur, Kleitman and his colleagues identified several stages of sleep. These stages were characterized primarily by the types of brain activity observed in each one. Furthermore, they noticed that there were many deviations from the average type of brain activity that characterized each stage, both within individuals from one night to the next, and across individuals on the same night. Before discussing their findings further, we first need to better understand how to measure and interpret averages (means) and individual deviations from these averages (variances).

Study Questions for Section 2-6

1. What kinds of evidence would scientific researchers consider to be best for describing sleep and dreams and for testing their theories?
2. Why do sleep researchers focus on these kinds of evidence?
3. What did Aserinsky and Kleitman (1953) initially predict about changes in brain activity during sleep?
4. How did the observations made by Aserinsky and Kleitman (1953) show this prediction to be incorrect?
5. What is rapid-eye-movement (REM) sleep? Why was its discovery important to Aserinsky and Kleitman?

Go to Quiz 2-6 questions

Go to Readings Section 2-7