Dement & Kleitman – Sleep and Dreams

What is the first main assumption of the biological approach?

Behaviour, cognition and emotions can be explained by the brain and the effects of hormones, genetics and evolution.

What is the second main assumption of the biological approach?

Similarities and differences between people are due to biological factors and how these interact with other factors such as environment and experience.

What are the two main types of sleep in Dement & Kleitman’s study?

REM (rapid eye movement) sleep and nREM (non-rapid eye movement) sleep.

How many stages does nREM sleep have?

Four stages.

What are ultradian rhythms in sleep?

90-minute rest–activity cycles that create repeating sleep stages (including REM and nREM) across the night.

What is a "dream" in the Dement & Kleitman study?

A vivid, generally visual sequence of imagery that usually occurs during REM sleep.

Why are dreams hard to study scientifically?

Because people are asleep and cannot communicate during dreams, and once awake researchers depend on subjective self-reports of dream content.

What does an EEG measure?

Electrical activity of the brain (patterns of brain waves).

What does an EOG measure?

Electrical activity of the eye muscles, showing the presence, size and direction of eye movements.

What do EEG patterns look like in REM versus nREM sleep?

In REM: low voltage, high frequency waves. In nREM: high voltage, slow waves or sleep spindles (short high-voltage, high-frequency bursts).

What was the overall aim of Dement & Kleitman (1957)?

To investigate dreaming objectively by examining the relationship between eye movements during sleep and dream recall.

What was specific aim 1 of Dement & Kleitman?

To test whether dream recall differs between REM and nREM sleep.

What was specific aim 2 of Dement & Kleitman?

To see whether there is a positive correlation between subjective estimates of dream duration and the length of the REM period.

What was specific aim 3 of Dement & Kleitman?

To test whether eye-movement patterns are related to dream content (visual dream experience or random CNS activity).

What research method and design did Dement & Kleitman use?

A laboratory experiment using observations, self-reports and correlational analysis with a repeated measures design.

Describe the sample in Dement & Kleitman (number and gender).

Nine adults: seven males and two females.

How were participants selected in Dement & Kleitman?

Opportunity sampling.

How were participants identified to keep their data confidential?

Using their initials instead of full names.

What pre-sleep instructions were given to participants?

They were told to eat normally but avoid alcohol and caffeine on the day of the experiment.

How were electrodes attached in the Dement & Kleitman study?

To the scalp for EEG and around the eyes for EOG, with the wires gathered into a "ponytail" so participants could move.

How were participants woken during the study?

By a loud doorbell that could wake them from any sleep stage.

What did participants do immediately after awakening?

They said whether they had been dreaming and then described the dream into a voice recorder.

How did the researchers define a "dream report"?

A coherent, fairly detailed description of dream content; vague fragments were not counted as dreams.

For aim 1, what was the independent variable (IV) and dependent variable (DV)?

IV: Sleep stage (REM vs nREM). DV: Whether the participant reported a dream and how detailed the report was.

For aim 2, what happened before waking the participants?

They were woken after either 5 or 15 minutes of REM sleep.

For aim 2, what were the IV and DV?

IV: 5 vs 15 minutes of REM before waking. DV: Participant’s choice (5 or 15 minutes) and the length of the dream report (number of words).

For aim 2, what extra analysis was carried out?

A correlational analysis between the estimated dream duration and the number of words in the dream narrative.

For aim 3, when were participants woken?

After they had shown a single eye-movement pattern (for example, mainly vertical) for more than a minute.

For aim 3, what were the IV and DV?

IV: Eye-movement pattern type (horizontal, vertical, mixed, or little/none). DV: Dream content report.

In the Dement & Kleitman study, how long did uninterrupted dream stages last?

Between about 3 and 50 minutes, with an average of around 20 minutes.

When did dream stages tend to be longer?

Later in the night.

How many rapid eye movements typically occurred in a dream stage?

Irregular bursts of between 2 and 100 rapid eye movements.

What percentage of REM awakenings produced dream recall?

About 79.6% (152 out of 191 REM awakenings).

What percentage of nREM awakenings produced dream recall?

About 6.9% (11 out of 160 nREM awakenings).

What does aim 1 show about dreaming and REM sleep?

People are far more likely to recall dreams when woken from REM sleep than from nREM sleep.

How accurate were participants when woken after 5 minutes of REM sleep?

88% correctly said they had been dreaming for 5 minutes.

How accurate were participants when woken after 15 minutes of REM sleep?

78% correctly said they had been dreaming for 15 minutes.

What correlation was found between dream duration estimates and narrative length?

A positive correlation (about 0.4–0.71); longer REM periods produced longer dream narratives.

Overall, were eye-movement patterns related to dream content?

Yes, eye-movement direction matched the visual content of the dreams.

Give an example of vertical eye movements linked to dream content.

A dream of climbing up a ladder and looking down.

Give an example of horizontal eye movements linked to dream content.

A dream of two people throwing tomatoes at each other.

What dream content was linked with little or no eye movement?

Viewing something in the distance.

What dream content was linked with mixed eye movements?

Talking to or looking at a group of people.

What is the main conclusion about REM sleep and dreams?

Dreams occur during REM sleep but rarely during nREM sleep.

According to Dement & Kleitman, when is dreaming most likely?

Towards the end of the night, when REM stages are longer.

What did the study conclude about eye movements and dreaming?

Eye-movement patterns reflect the visual experience of dreaming.

Give one reason Dement & Kleitman has high internal validity.

The concept of a "dream" was clearly defined and participants were not told about their sleep stage, reducing demand characteristics.

Give one reason the study has high reliability.

EEG and EOG provided objective, quantitative data and the procedure was standardised.

Give one reason Dement & Kleitman has low generalisability.

It used only nine participants, mainly male, all from one country.

Give one reason the study has low ecological validity.

Participants slept in a laboratory, attached to electrodes, and did not follow their usual caffeine or alcohol habits.

State an ethical issue in the Dement & Kleitman study.

Participant WD was deceived about whether he was woken from REM or nREM sleep.

Give one real-life application of Dement & Kleitman’s findings.

EEG can be used to monitor sleep stages and help diagnose and treat sleep disorders such as insomnia or parasomnias.

How does Dement & Kleitman relate to the nature–nurture debate?

It emphasises nature by showing that dreaming is strongly linked to biological REM processes recorded by EEG.