dement and kleitman (sleep and dreams)

stages 1 and 2 of sleep

light sleep

easily woken

stages 3 and 4 of sleep

deeper sleep

brain waves have higher amplitude and lower frequency than brain waves in stages 1 and 2

REM sleep

lower amplitude/higher frequency brain waves

similar to wakefulness

eyelids move quickly

muscle inhibition

sensory blockade

dreaming occurs

ultradian rhythms

bodily cycles that repeat more than once every 24 hours.

during the night, we move through several 90-minute sleep cycles.

earlier in the night, the cycles include a higher proportion of non-REM (NREM) sleep.

later in the night, we spend more time in stages 1, 2 and REM sleep.

aims

to investigate whether dream recall is more common in REM than in NREM sleep.

to investigate whether participants can accurately estimate the duration of their dreams.

to investigate whether eye movements (vertical/horizontal) correspond with dream content.

to investigate whether there is a correlation between the duration of a REM sleep episode and the number of words (the narrative) used to describe any dreams experienced.

research method

experiment

research design

repeated measures design (aims 1–3)

correlation (aim 4)

data collection techniques

self-reports

interviews

dependent variables

whether a dream was reported or not (quantitative data) – dream has to be described in detail to be counted

perceived duration of dream - initially participants were asked to report dream length in minutes, then participants were instead asked whether they had been dreaming for 5 or 15 minutes (quantitative data)

verbal description of dream content/narrative (qualitative data) - number of words used (quantitative)

independent variables

whether participants were woken:

during REM or NREM sleep

following 5 or 15 minutes of REM sleep

following REM sleep with mainly vertical, mainly horizontal, mixed or limited eye movements

control variables

All participants abstained from alcohol and caffeine on the day of the study

All participants reported to the laboratory at their normal bedtime.

The same loud doorbell was used for all awakenings.

The positioning and number of electrodes was standardised (2–3 near the eyes and on the scalp).

sample

seven men and two women (five were studied in depth, and four were studied to confirm results)

sample was from Chicago, USA

procedure

participants slept in a quiet, dark room at the University of Chicago with electrodes placed near the eyes and on the scalp (wires were tied together to stop them from becoming tangled and the EEG machine was in an adjoining room).

participants were woken several times each night to self-report all the dependent variables using a bedside recording device.

the researchers chose when to wake the participants using the EEG and a timer, and listened to the self-reports from the adjoining room.

researchers occasionally entered the sleep room to interview the participant about their dream, but they never revealed information about sleep stage or direction of eye movements when questioning the participants.

ethical evaluation

confidentiality - this was maintained as participants were referred to using their initials and dream content was not paired with their initials.

results

REM sleep never occurred immediately after sleep onset.

all participants had regular REM sleep periods throughout the night.

one REM period occurred every 92 minutes (range 70–104 minutes).

average REM sleep duration was 20 minutes (range 3–50 minutes).

longer REM sleep periods occurred later in the night.

one participant (DN) had a lower accuracy rate of only 65%: he underestimated dream length and was only correct 50% of the time when woken after 15 minutes.

correlation coefficients for REM duration and length of dream report (number of words) for each participant ranged from +0.40 to +0.71 and the average was +0.58.

(check notion for results table)

conclusions

dreams are more likely to be reported in REM than NREM sleep.

dreams are experienced in real time (dream length and REM sleep duration match).

eye movements in sleep are not random, they match dream content.

the subjective experience of dreaming can be measured objectively using EEG to identify REM sleep.

strengths

reliable - the procedure was standardised, meaning the study can be replicated to test for reliability.

objective - the use of quantitative EEG data removed bias when deciding whether sleep was REM or NREM.

weaknesses

lacked validity - some data was discarded as recordings were too muffled and dreams could not be accurately transcribed.

not generalisable - only nine people were studied (only five in detail) and ages and occupations were not provided so individual differences may have affected results.

applications to everyday life

understanding typical patterns of sleep and dreaming is important.

psychologists can identify people whose sleep and dreams are unusual.

people are more likely to receive suitable treatment/support to improve sleep quality.

nature

all participants demonstrated ultradian REM/NREM sleep cycles and dreamed more during REM than NREM.

this suggests these patterns are innate and may help us to survive.

nurture

dream content was diverse.

differing life experiences affect what we dream about and may affect the duration of REM sleep.