Dement and Kleitman

• Name of Researchers and Date : Dement and Kleitmen 1957
• Title of Research Study: Sleep and Dreams
• One Assumption of the Biological Approach:

  • Behaviour, cognitions and emotions can be explained in terms of the working of the brain and the effect of genetics, hormones and evolution.
• One Assumption of the Biological Approach:

  • Similarities and differences between people can be understood in terms of biological factors and their interaction with other factors
• The Psychology Being Investigated:

  • Sleep and its stages 
  • Ultradian rhythms - bodily cycles that repeat more than once every 24 hours 
  • During the night we move through 90-minute sleep cycles
  • The composition of those cycles changes as we move through the night
• Aims of the Study:

  1. Whether dream recall is more common in REM than NREM
  2. Whether participants can accurately estimate the duration of their dreams
  3. Whether the type of eye movements correspond with dream content 
  4. To see if there is a positive correlation between the length of REM and the number of words given in a dream narrative
• Hypothesis:

  • Does dream recall differ between REM and NREM sleep?
• Independent and Dependent Variables Study 1:

  IV - whether in REM or NREM sleep

  DV - was a dream reported and if so, detail
• Methodology used in this Study:

  • Study 1 & 3 - Natural Experiment in a laboratory setting
  • Study 2 - True experiment - Repeated measures + correlation
• Independent and Dependent Variables Study 2:

  IV - waking up after 5 or 15 minutes after the onset of REM

  DV - perception of whether they had been dreaming for 5 or 15 minutes
• Independent and Dependent Variables Study 3:

  IV - Eye movement pattern before waking:

  (a) mainly vertical eye movements,

  (b) mainly horizontal eye movements,

  (c) both vertical and horizontal eye movements, and

  (d) very little or no eye movements

  DV - The  description of their dream
• Details about Participants:

  • Nine adult participants (initially)
  • Seven male, two female 
  • Five studied in detail - spent between 6 and 17 nights
  • Took place in a sleep laboratory at the University of Chicago (USA)
• Sampling Technique: Volunteering Sampling
• Research Designs Used in the Study:

  • Longitudinal Case Study - Involves collecting data over an extended time
  • Positive correlation - The longer they dreamt, the more words about the dream were written down
• Overall Findings:

  • The frequency of periods of REM was constant for each participant, but the length varied between them (ranging from 70 to 104 minutes, with an average of 92 minutes)
  • The duration of REM varied from 3 to 50 minutes, with an average of 20 minutes. REM periods were also longer later in the night.
• Overall Findings:

  • All 9 participants showed a regular pattern of sleep and EEG recordings, which were characterised by periods of deep sleep (high-voltage, slow pattern of EEG activity) followed by periods of REM sleep (low-voltage, fast pattern of EEG activity)
  • Dement and Kleitman found that REM sleep never occurred immediately after the onset of sleep but did occur at regular intervals throughout the night.
• Study 1 Findings:

  • Dream recall occurred predominantly in REM sleep.
  • Participants had a high incidence of dream recall following REM awakenings (80%)
  • A low incidence of recall following non-REM awakenings (7%)
• Study 2 Findings:

  • All participants were able to determine whether they had been dreaming for 5 or 15 minutes with high accuracy (correct 83% of the time from 111 awakenings) 
  • With the exception of one participant who was only correct 65% of the time and tended to underestimate the length of the time he had been dreaming
• Study 3 Findings:

  • Vertical eye movement dream reports included looking at climbers on a cliff, climbing ladders and throwing a basketball.
  • The only dream report following horizontal eye movements involved watching two people throwing tomatoes at each other
  • Little or no eye movement dream reports included driving a car
  • Mixed eye movement dream reports included talking to a group of people, searching for something and fighting with someone
• Study 4 Findings:

  • There was a moderate positive correlation between duration of REM and number of words in  dream narrative. 
  • The average correlation coefficient was +0.58, with individual results ranging from +0.40 to +0.71.
• Study 4 Co-Variables:

  Co-variable 1: the number of minutes spent in REM sleep

  Co-variable 2: the number of words in the corresponding dream narrative recording
• Conclusions Drawn:

  • Dreams  almost certainly occur during REM
  • Dreams happen in real time
  • Eye movement correspond to what the content of the dream
  • Dreams can be measured objectively using a EEG to identify REM sleep
• How Can the Information Found be Used:

  • Treating sleep issues - An EEG can be used to determine when a person is in REM or non-REM sleep and can, therefore, be used to support the diagnosis of sleep issues (as some sleeping disorders only occur in some stages of sleep).
• Strengths of the Study:

  • Ethics - confidentiality remained - used initials + no other information about ppts was told
  • Reliability - high level of standardised procedure
  • Validity - ensured nobody else was present when the participants recalled their dreams
  • Quantitative Data - number of words in the dream narrative was calculated and correlated against the amount of time spent in REM sleep
• Weaknesses of the Study:

  • Generalising - significant variation in the duration of sleep cycles even between the small number of five main ppts (e.g. one ppt averages one period of eye movement every 70 mins while another every 104 mins)
  • Lacks ecological validity - slept in a lab with EEG w/ electrodes attached to them on their heads - could've affected normal sleep patterns + difficult to fully relax
• Weaknesses of the Study:

  • Some results discarded - out of 152 dreams recalled, 6 recordings were discarded (couldn't understand) - validity is the affected
  • Individual differences - operational definition of dream length - some might have a significant difference in how verbal the ppts are
  • Self-report - people could feel embarrassed about their dream OR not remember it
• Nature Debate:

  • All participants reported a significantly greater number of dreams during REM sleep than non-REM sleep, indicating that dreaming during REM sleep is an innate biological mechanism. Furthermore, regularly occurring periods of REM were observed in all participants on every night of sleep, indicating that this ultradian rhythm is universal for all humans and is biologically
• Nurture Debate:

  • People had such diverse dreams with differing content demonstrates the role of nurture in sleep and dreams, as our different life experiences will impact what we dream about.