Dement & Kleitman

Psychology

  • Sleep and Dreams

  • Dement, W. and Kleitman, N.

  • 1957

  • Biological Approach:

    • How we think, act, and feel is influenced by our brains and the effects of hormones, evolution, and genetics

    • Similarities and differences in individuals can be explained by biological factors and their interactions with other factors (environment, people, etc.)

  • Circadian rhythm (24-hours) and ultradian rhythm (90 minutes) control the stages of sleep

  • Stages of sleep:

    • NREM (Non-Rapid Eye Movement): Comprises three stages, including light sleep (Stage 1), moderate sleep (Stage 2), and deep sleep (Stage 3); quiescent

    • REM (Rapid Eye Movement): Occurs approximately every 90 minutes, characterized by vivid dreams, increased brain activity, and plays a significant role in memory consolidation and emotional regulation.

  • Electroencephalograph (EEG) records changes in electrical brain activity

    • Produces a chart of brain waves with differing frequencies and amplitudes (heights)

  • Over time, dream sleep increases and depth of cycle decreases

  • EEG produces EOG recording of eye movement frequency and direction

Background

  • Askerinsky and Kleitman (1955) found:

    • When woken from REM, participants were more likely to recall a vivid dream

    • REM has alpha waves (like electrical activity when awake)

    • Eye movements are simultaneous and occur in 90 minute cycles

    • REM has increased breathing and heart rate, indicating changes in brain activity

    • Eye movements could correlate with visual activity of dreams

Aim

  • “To find objective methods to demonstrate a relationship between dream content and physiological indicators of dreaming, such as eye movements”

  • Questions:

    • Does dream recall differ between REM and nREM stages of sleep?

    • Is there a positive correlation between subjective estimates of dream duration and the length of the REM period before waking?

    • Are eye-movement patterns related to dream content?

Procedure

  • IV 1: Sleep Stage of Awakening

    • Participants were woken either in REM or nREM (but not told which).

      • PM and KC awoken based on a random number table

      • DN awoken 3 times during REM then 3 times during nREM

      • WD told he would only wake up during REM, but was really awoken randomly

      • IR awoken based on experimenters’ choice

    • They confirmed whether they were having a dream and described the content in a recorder.

    • IV = Timing of awakenings (during REM or NREM periods)

    • DV = whether a dream was reported or not.

    • DV = report of dream narration content.

  • IV 2: Duration of REM Sleep

    • Participants were awoken randomly after either 5 or 15 minutes of REM sleep.

    • Initially, participants were asked to estimate the length of time in REM sleep to the nearest minute.

      • In the revised procedure participants were given a fixed choice and asked if they were dreaming for 5 or 15 minutes.

    • The number of words in the dream narrative was counted (although this was affected by how expressive the participant was).

    • IV = randomly woken after 5 or 15 minutes.

    • DV = dream duration:

      estimate which duration (5 or 15 minutes) they had been dreaming

      the number of words in the dream narrative was counted as a measure of dream length.

  • IV 3: Pattern of Eye Movement during REM Sleep

    • The direction of eye movements was detected using electrodes around the eyes (EOG).

    • The eye movement patterns were: mainly vertical, mainly horizontal, both vertical and horizontal, and very little or no movement.

    • Participants were woken after the persistence of a single eye movement pattern for more than one minute and asked to report their dream.

    • IV = eye movement pattern type (not manipulated by researchers, so natural experiment)

    • DV = report of dream content.

  • Sample

    • 9 adult participants, were predominantly male (7 males and 2 females).

    • The five main participants were studied intensely: spending between 6 and 17 nights in the laboratory.

    • The other four participants were used to confirm the results of the main participants: spending only 1 to 2 nights in the lab.

    • All participants were identified by their initials in the study.

    • The researchers do not provide information about how the participants were recruited or selected, nor do they mention any specific demographic details beyond gender.

  • Apparatus

    • Bed

    • EEG

    • Wires in ponytail

    • Electrodes on eyes and scalp

    • Quiet, dark room in laboratory

    • Doorbell

    • Tape Recorder

  • Controls

    • No caffeine or alcohol each day of study

    • Normal bedtime

    • Loud doorbell but not alarming

    • Experimenters waited to ask questions until participants had fully awakened to ensure accurate recall of their dreams and experiences during REM sleep

    • Dreams must be described (not vague)

    • Operationalized

Ethics

  • WD deceived about which stage of sleep he would wake up in

    • Could cause distress from no informed consent

  • Positive = kept confidentiality

Results

  • All participants dreamed each night

  • Uninterrupted dream stages:

    • last 3-50 minutes (sample mean = 20 min)

    • longer later in night

    • showed bursts of 2-100 REMs

  • No REM seen in onset of sleep

  • Cycle length varied between individuals (sample mean = 92)

  • When woken from nREM, participants fell back asleep in nREM

  • When woken from REM, participants fell back asleep in nREM until next cycle

  • IV 1: Sleep Stage of Awakening

    • 79.6% (152 of 191) of awakenings in REM recalled dreams

    • 6.9% (149 of 160) of awakenings in nREM recalled dreams

    • 29% (5 of 17) nREM awakenings after the end of REM recalled dreams

    • Only 6 of 132 awakenings in nREM after 8 minutes were dream recalls

    • nREM awakenings described feelings over details (felt anxious, pleasent, or detached)

    • DN had same results even if he could learn awakening patterns

  • IV 2: Duration of REM Sleep

    • 88% of estimates correctly guessed 5 minutes

    • 78% of estimates correctly guessed 15 minutes

    • Correlation r varies between r=0.4 and r=0.71

    • Narratives after 30-50 minutes were not much longer than 15 minute dreams

  • IV 3: Pattern of Eye Movement during REM Sleep

    • Based on 35 awakenings (9 participants)

    • 3 mainly vertical eye movements:

      • Operating hoist at bottom of cliff

      • Climbing ladders

      • Throwing basketballs

    • 1 horizontal eye movement:

      • Tomato Fight

    • 10 little or no eye movement”

      • watching something in the distance

    • 2 had eye movement to left by awakening:

      • Startled by car when driving

      • Acknowledged person when driving

    • 21 mixed eye movements

      • Close by, looking for something, or fighting

    • Used control eye movement patterns from awake participants

Conclusions

  • Dreaming happens in REM (more likely at the end of the night), not nREM

  • People can judge length of dreams

  • REM patterns relate to dream content

  • nREM dream recalls come from prior REM

  • Dreams progress in ‘real time’

Strengths

  • Lab environment controlled participant variables

  • Deception and disinformation on awakenings reduced demand characteristics

  • Change from open question to 5 or 15 minute improved validity

  • Operationalized dream definition

  • EEG provided objective data

  • Narratives gave qualitative insight

Weaknesses

  • Small sample with more men (7) than women (2)

  • Volunteer sampling means participants may have dreams more frequently or remember dreams better, prompting them to volunteer for this study

  • Regular coffee or alcohol drinkers could have atypical dreams/results without said drinks

  • Lab environment is atypical for people, decreasing ecological validity