Dement & Kleitman (sleep and dreaming)

Sleep is difficult to study

Participant is asleep and unable to communicate with the researcher. When awake only self-report data can be collected. Might not be valid and is subjective.

EEG

Electro-encephalogram

EEG measures

Detects and records electrical activity from nerve and muscle cells, showing brain wave frequency and amplitude over time.

EOG

Electro-oculogram

EOG measures

Eye movements

REM

Rapid eye movement sleep

nREM

Non rapid eye movement sleep

nREM stages

1-4, where 1 is the lightest, 4 is the deepest

Ultradian Rhythym

A cycle that repeats more often than daily, ex. the occurrence of periods of dreaming every 90 minutes during sleep

How is REM sleep similar to wakefulness

Eyes move, experience vivd (if bizarre) thoughts in the form of dreams, our brains are active

How is REM sleep different from wakefulness

Fairly insensitive to external stimuli, paralyzed

Ideas about what dreams are

Dreams have unconscious meanings, Dreams are the results of random firing of neurons, Dreams resolve cognitive and emotional problems we currently have in our waking state

Overall aim

To investigate dreaming in an objective way by looking for relationships between eye movements in sleep and the dreamer's recall

Aim 1

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

Aim 2

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

Aim 3

To test whether eye-movement patterns are related to dream content

Main research method

Experimental

Method of Aim 1

Experiment with repeated measures design. The IV was whether the participant was woken from REM or nREM sleep. The DV was whether they recalled a dream or not.

Method of Aim 2

Correlation. A further comparison of participants' estimates of whether they had been dreaming for 5 or 15 minutes. Another repeated measures design experiment.

Method of Aim 3

Relationships between eye-movement patterns and dream content, self-reports were compared to the direction of eye movements observed. Also repeated measures design experiment.

Sample

Nine adult participants

Gender of participants

7 male

2 female

Experimental design

Repeated measures

Aim 1 IV

REM sleep/nREM sleep

Aim 1 DV

Whether a dream was reported and, if so, the detail

Aim 2 IV

Waking after 5 or 15 minutes

Aim 2 DV

Participants' choice of 5 or 15 minutes

Aim 3 IV

Eye-movement pattern type

Aim 3 DV

The report of dream content

Eye-movement patterns detected

Mainly vertical

Mainly horizontal

Both vertical and horizontal

Very little or no movement

Before arriving to the lab

Ate normally excluding caffeine-containing drinks and alcohol.

When did participants arrive to the lab?

Just before their normal bedtime

Describe the sleeping conditions

Went to sleep in a dark, quiet room with electrodes attached beside the eyes and on the scalp, which fed into the experimenters' room . The wires were gathered together into a single cord from the participant's head (like a pony-tail) so they could move easily in bed.

How did the researchers wake the participants up?

By a doorbell

How long did it normally take the participants to fall back asleep?

5 minutes

Counted as a dream if:

Coherent, fairly detailed description of the content

How many awakenings occurred in the first two hours of being asleep?

21%

How many awakenings occurred in the second two hours of being asleep?

29%

How many awakenings occurred in the third two hours of being asleep?

28%

How many awakenings occurred in the fourth two hours of being asleep?

22%

Procedure Aim 1

Participants were woken either from REM or nREM sleep but were not told which. The choice of REM and nREM waking was decided in different ways for different participants. Participants stated whether they were having a dream or not and then, if appropriate, described the content of the dream into a recorder. When the participant had finished, the experimenter occasionally entered the room to ask further questions about the dream (they were given a brief interview).

These participants were randomly awoken (controlled & systematic - number table)

PM and KC

This participant was woken in groups of three REM then three nREM

DN

This participant was told they would only be woken in REM but actually woke them in REM or nREM randomly

WD

This participant was woken in no specific order (experimenters' whim)

IR

Procedure for Aim 2

Initially, participants were woken after a variety of REM durations and asked to estimate the time they had been dreaming. Although roughly accurate, this was too difficult for participants. Subsequently, they were woken after either 5 or 15 minutes in REM sleep. The participant guessed which duration they had been dreaming for. Longer REM periods were also used. The number of words in the dream narrative after each duration, if given, was counted.

Procedure for Aim 3

The direction of eye movements was detected using EEG electrodes around the eyes. Participants were woken after a single eye-movement patter had lasted for more than 1 minute and asked to report their dream. Comparison EEG records were taken from awake participants, 20 naive ones and five of the experimental sample, who were asked to watch distant and close-up activity.

How was the experiment controlled?

1. Loud doorbell to wake up Ps from light or deep sleep.

2. E only asked questions after recording was completed.

3. Not counted as dream if participant recalled dreaming but could not remember content.-OPERATIONALIZED.

4. Participant reported to lab slightly before regular bedtime.

5. Asked to eat normally.

6. Asked to refrain from caffeine-containing and alcoholic beverages on day of experiment.

Findings about onset of sleep

No rapid eye movements were seen during the onset of sleep even though the EEG passed through a stage of brain waves similar to those produced during REM sleep

Findings about cycle length

The cycle length (from one REM stage to the next) varied between participants from 70 to 104 minutes (with a mean of 92 minutes for all participants), but was consistent within individuals

Findings about 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 movement

How did dream recall differ between REM and nREM sleep?

Participants frequently recalled dreams when woken from REM sleep, but rarely recalled dreams when woken from nREM sleep.

What percentage of REM awakenings led to dream recall?

79.6% of REM awakenings (152 out of 191) resulted in dream recall.

What percentage of nREM awakenings led to no dream recall?

93.1% of nREM awakenings (149 out of 160) resulted in no dream recall.

When was the difference between REM and nREM dream recall most noticeable?

At the end of the nREM period

What percentage of dreams were recalled when participants were woken from nREM sleep within 8 minutes of a REM stage?

29% (5 out of 17 awakenings).

What percentage of dreams were recalled when participants were woken from nREM sleep more than 8 minutes after a REM stage?

Less than 5% (6 out of 132 awakenings).

What did participants typically describe when woken from nREM sleep?

They described vague feelings or emotions (e.g., anxiety, pleasantness, detachment) but not specific dream content.

During which stage of sleep were participants least likely to remember dreams?

During Stage 2 sleep, when EEG readings show sleep spindles.

What was significant about participant DN in Dement and Kleitman's study?

DN was no more or less likely to report dreams in REM or nREM sleep than others, showing he did not learn the awakening pattern.

Did participants improve in dream recall accuracy over time?

No, participants did not become more accurate or improve with practice.

Did every REM awakening produce dream recall in Dement and Kleitman's study?

No — awakenings from REM did not always lead to dream recall.

When was the absence of dreaming in REM most common?

Early in the night

How many REM awakenings had no dream reported overall?

39 REM awakenings had no dream reported.

How were the 39 REM awakenings without dreams distributed across the night?

19 in the first 2 hours

11 in the second 2 hours

5 in the third 2 hours

4 in the last 2 hours

What were the two comparisons made to test dream duration accuracy?

Comparing subjective estimates of dream duration with actual REM duration.

Comparing measured REM duration with the length of participants' dream narratives.

When participants had to estimate if they had been dreaming for 5 or 15 minutes, how accurate were they?

Accuracy was 88% for 5-minute dreams and 78% for 15-minute dreams.

What was the correlation (r) between REM duration and the number of words in dream narratives?

The r values ranged from 0.4 to 0.71, all showing significant positive correlations.

What does the positive correlation between REM duration and narrative length suggest?

The longer the REM period, the longer and more detailed the dream narrative tended to be.

Why weren't dream narratives after 30-50 minutes of REM much longer than those after 15 minutes?

Participants probably couldn't remember all the details from very long dreams.

How many awakenings and participants were used for the eye-movement analysis?

35 awakenings from nine participants.

Were periods of purely vertical or purely horizontal eye movement common?

No, they were very rare.

What type of eye movement occurred in dreams where participants were watching something in the distance or staring at an object?

Little or no eye movement.

Give an example of a dream with little or no eye movement.

The dreamer was driving a car and staring at the road ahead (sometimes startled by something appearing to the left).

What was reported in dreams with mixed eye movements?

Participants looked at nearby objects or people, such as talking to a group, looking for something, or fighting.

What was the relationship between eye-movement patterns in dreams and those in awake participants?

They were similar in amplitude and pattern — little movement for distant viewing and more for close-up activity.

When were vertical eye movements seen in awake participants?

Only during blinking or when the experimenter threw a ball in the air.

What kinds of dreams were linked to mainly vertical eye movements?

Dreams that involved looking up and down actions, such as operating machinery, climbing ladders, or shooting basketballs and picking up the ball again.

What dream content was linked to horizontal eye movements?

Watching side-to-side activity, such as observing two people throwing tomatoes at each other.

Why is EEG measurement more valid than relying on dream recall alone?

Because EEG provides objective evidence, while dream recall is subjective and can be affected by forgetting.

What evidence supports the idea that dreams occur in real time?

EEG recordings of eye movements and brain waves showed consistent patterns matching the length and content of dreams.

Why might dreams sometimes be recalled during nREM sleep?

Because participants may be remembering dreams from a previous REM phase, especially if woken soon after REM.

When during the night is dreaming most likely to occur?

Toward the end of the night, when REM stages become longer.

What are the three main conclusions Dement and Kleitman drew from their study?

Dreams probably occur only during REM sleep.

Dream length is related to the length of the REM period, suggesting dreams happen in real time.

Eye movements during REM correspond to where and at what the dreamer is looking in the dream.

What does the relationship between REM duration and dream duration suggest about the nature of dreams?

It suggests that dreams occur in real time, not as instant events.

How do eye movements in REM compare to those when awake?

They are similar in amplitude and pattern to eye movements experienced during wakefulness

How was "dream" operationalized in Dement and Kleitman's study?

A dream was defined as a recollection that included content, not just the impression of having dreamt. This increased validity, ensuring real dreams were being recorded.

Why was the EEG an important methodological tool?

The EEG provided an objective and reliable biological measure of dreaming through brain waves and eye movements, reducing researcher bias.

What type of data did the study collect?

Both quantitative data (EEG readings, number of REMs, duration) and qualitative data (dream reports describing content).

How did the researchers ensure reliability?

Consistent electrode placement and standardized procedures meant recordings were replicable and similar to previous findings.

How was generalisability addressed in terms of gender?

Both men and women were included, which increased generalisability slightly, though the sample was small (9 participants).

Why might generalisability still be limited?

Participants volunteered for a dream study and may have been better at recalling dreams or had different sleep patterns than the general population

Why might ecological validity be low?

Participants slept in a laboratory, connected to machines and observed, which was an unnatural sleep environment.

How might ecological validity have been further affected?

Participants had to avoid caffeine and alcohol, making sleep less typical than in normal life.

What was a key strength of this laboratory experiment?

High standardization and control (EEG, doorbell sound, pre-study instructions) made replication easy and results reliable.

Strengths of Lab Experiment (general)

Lab experiments have high levels of standardization and so can be replicated to test for reliability.

As lab experiments have high levels of control. researchers can be more confident it is directly affecting the DV.

How did the EEG increase the validity of the Dement and Kleitman study?

The EEG objectively measured brain activity and eye movements, providing biological evidence of REM and nREM sleep. This reduced researcher bias and improved internal validity.

Why might volunteer bias affect the results of the Dement and Kleitman study?

Participants chose to take part in a dream study and may have been unusually interested in dreaming or better at recalling dreams than the general population.

Why might the Dement and Kleitman study be considered reductionist?

The study focused mainly on biological mechanisms of dreaming and did not consider psychological or emotional influences on dream content.

Why is the use of self-reports a limitation in the Dement and Kleitman study?

Participants' dream descriptions may have been inaccurate or incomplete because dream memories can fade quickly, reducing validity.