Dement and Kleitman (Sleep and Dreams) Flashcards
AIM:
To find more about dreaming, specifically to answer these three questions:
• Does dream recall differ between rapid eye movement (REM) and quiescent (nREM) stages of sleep? meaning, will individuals remember their dreams differently in REM and NREM.
• Is there a positive correlation between subjective estimates of dream duration and the length of the REM period before waking? meaning, will the real duration of the REM length coincide with the individual’s assumption about its length.
• Are eye movement patterns related to dream content? meaning, is what we dream influencing how our eyes move during sleep.
SAMPLE:
Initially, 9 adults were recruited to participate in the study - 7 males and 2 females. However, only 5 participants were studied in detail. The results from the other 4 were used to confirm the reliability of the other 5.
BACKGROUND:
• Aserinsky and Kleitman (1955) were first to use an EGG (a machine that detects the activity of nerve muscles) to investigate the relationship between sleep and dreaming.
• They found that humans have several sleep stages during the night, which alternate between REM and NREM.
• They reported that those participants woken up during the REM sleep stage reported more vivid and visual dreams.
PROCEDURE: (1)
Prior to the study the participants were instructed to abstain from drinking caffeinated beverages and alcohol. They were expected to arrive at the laboratory just before their usual bedtime. They had to sleep in a dark room with electrodes attached to their scalp and the wires gathered in a ponytail. They were woken at various times during the night by a loud doorbell and had to describe their dreams in a tape recorder and go back to sleep. The reports were operationalized as dreams if the participants could actually recall its content and not just a feeling or impression of it.
PROCEDURE: (2)
• For question 1, participants were woken either during their REM or nREM sleep stages, this was decided either using a random number table, in groups of three, deceiving the participant in which sleep stage they were woken up in or at the experimenter’s choice. If necessary, after recording their dream, the experimenter entered to ask further questions. There was no other communication between the experimenter and the participants.
• For question 2, participants were woken during REM sleep, at either 5 or 15 minutes after entering the stage. They had to guess the duration of their dream. Longer REM periods were also used. The number of words used to describe the dream narrative, if given, was also counted.
• For question 3, participants were woken after a particular eye-movement pattern was recorded by the EGG for more than a minute and asked to report their dream.
The eye-movement patterns detected were: mainly vertical, mainly horizontal, both vertical and horizontal and very little or no eye movement.
The reports were compared to 20 others from woken participants instructed to watch distant and close activities.
RESEARCH METHOD:
This was a laboratory experiment since all participants had to sleep in a laboratory, away from their usual environment, with electrodes from the EGG attached to them.
EXPERIMENTAL DESIGN:
The experiment had a repeated measures design since all participants generally underwent the same procedure, however, to find answers to specific questions, there were sometimes slight differences for some participants.
VARIABLES:
• For question 1, the independent variable was whether participants were woken up in REM or NREM and the dependent variable was how well they recalled their dream.
• For question 2, the independent variable was whether the participants were woken up after 15 or 5 mins in REM sleep. The dependent variable was whether their subjective guess of the real duration was right.
• For question 3, the independent variable was the specific dream content and the dependent variable was specific eye-movement patterns in relation to dream content.
RESULTS: (1) Intro
Dement and Kleitman reported some general findings, such as that all participants dreamed every night, as well as those relating to their three questions. They found that uninterrupted dream stages:
• lasted 3-50 minutes (with a mean of approximately 20 minutes)
• were typically longer later in the night
• showed intermittent bursts of around 2-100 rapid eye movements.
In addition, they observed that:
• No rapid eye movements were recorded at the beginning of REM sleep.
• The cycle length (from one REM stage to the next) varied between participants from 70 to 104 minutes (with a mean of 92 minutes), but was consistent within individuals.
• Participants tended to return back to NREM when woken on NREM but when woken in REM sleep they typically did not dream until the next REM phase.
RESULTS: (2)
Question 1
• Results from question 1:
79% of participants who were woken up in REM produced a dream recall and 93% in the NREM didn’t. The absence of dreaming in REM was more common early in the night. In NREM awakenings, participants tended to describe feelings but not specific dream content. Participants did not become more accurate over time i.e they didn’t learn the pattern of their awakenings through practice.
RESULTS: (2) Question 2
• Results from question 2:
88% of participants guessed the 5 minutes correctly and 78% of them guessed the 15 minutes correctly. The dream duration and the number of words used to describe the dream narrative were significantly positively correlated.
RESULTS: (2) Question 3
• Results from question 3:
Periods of only horizontal and only only vertical were rare.
There were 3 dreams with mainly vertical eye movements. In one dream, the participant was standing at the bottom of a tall cliff operating at a hoist (a lifting machine) and looking up at climbers at various levels then down at the machine. In another dream, a man was climbing up a series of ladders looking up and down as he climbed. In the third dream, the participant was throwing basketballs at a net, shooting, looking up at the net, and then looking down to pick up another ball from the floor.
There was one instance of a dream with horizontal movement, in which the dreamer was watching two people throwing tomatoes at each other.
Ten dreams had little or no eye movement and the dreamer reported watching something in the distance or staring at an object. (Two of those awakenings also had several large eye movements to the left just a second or two before awakening. In one, the participant had been driving the car and staring at the road ahead. He approached a road junction and was startled by a speeding car appearing to his left (as the bell rang))
21 of the awakenings had mixed eye movements. These participants reported looking at objects or people close to them, for example talking to a group of people, looking for something and fighting with someone.
The eye-movement patterns recorded from the awake participants were similar in amplitude and pattern to those occuring in dreams.
CONCLUSION:
🔹The results indicate that dreaming is experienced in REM but not nREM sleep, participants can judge the length of their dream duration and REM patterns relate to dream content.
🔹Dreaming is more likely at the end of the night, as REM stages are longer.
🔹The occasional recall of dreams from nREM is likely to happen because dreams are being remembered from the previous REM phase, and this is more likely closely following REM sleep.
🔹 Measurements using EEG to record eye movements and brain waves show that differing stages of brain activity and the presence or absence of dreams provides objective evidence supporting the idea that dreams progress in real time.
EVALUATION: (Strengths)
🔷 High Reliability - The study was a laboratory experiment. It was therefore possible to limit the effects of extraneous variables. For example, if some individuals, or participants in different stages of sleep, had woken more slowly they may have forgotten more of their dream. This was avoided by using a loud doorbell that woke them instantly from any sleep stage.
🔷 High Validity - Another strength was that the study was highly operationalized. For example dreams being clearly defined as a recollection that included content rather than just a feeling or impression of it. This helped to raise validity, as Dement and Kleitman could be sure that the details being recorded were of dreams.
EVALUATION: (Weaknesses)
🔷 Low Generalizability - The study only included nine participants in total, the small size of the sample limits generalizability. As these individuals had chosen to participate in a study on dreaming, they may have dreamed more frequently than the population in general, remembered their dreams better, or had more visual dreams for example.
🔷 Low Ecological Validity - Several aspects of the procedure potentially reduced the ecological validity of the findings. People who were used to drinking coffee or alcohol could have experienced sleep or dreams that were not typical for them as they had been asked to refrain from those drinks. Also there was no mundane realism as all participants would have found sleeping in a laboratory, connected to machines and under observation, quite different from sleeping in their normal bed. This could also have made their sleeping behaviour less typical.
