Why is "Swapping EEG and EOG (saying EEG measures eye movements)" a common mistake in Dement & Kleitman (Sleep and Dreams)?

Why it happens: The abbreviations look similar. How to avoid it: EEG = brain (E for encephalo). EOG = eyes (O for oculo). Memorise the 'O = eye' link. Source: 9990 mark schemes

Why is "Knowing only 'REM = dreaming' and missing the other two hypotheses" a common mistake in Dement & Kleitman (Sleep and Dreams)?

Why it happens: Students learn the headline finding only. How to avoid it: Learn all three: (1) REM↔dreaming; (2) REM length↔estimated dream length; (3) eye direction↔dream content.

Why is "Describing results without any figures" a common mistake in Dement & Kleitman (Sleep and Dreams)?

Why it happens: Students remember the trend but not the numbers. How to avoid it: Quote ≈80% (REM) vs ≈7% (nREM) and '5 or 15 minutes' for the duration test — these are markable facts.

Why is "Generic evaluation ('small sample') without saying who was in it" a common mistake in Dement & Kleitman (Sleep and Dreams)?

Why it happens: Stock evaluation phrases. How to avoid it: Be specific: '9 participants, mostly male, only 5 studied in detail' → poor generalisability. Specific + explained = top band. Source: 9990 Learner Guide example responses

Why is "Claiming REM 'causes' dreaming with certainty from the correlational parts" a common mistake in Dement & Kleitman (Sleep and Dreams)?

Why it happens: Confusing the experimental and correlational elements. How to avoid it: Tests 2 and 3 are correlational — they show relationships, not cause. Phrase carefully: REM is 'strongly associated with' dreaming.

Biological Approach (AS Level)Cambridge International A Level Psychology 9990

Dement & Kleitman (Sleep and Dreams)

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Dement & Kleitman (Sleep and Dreams) — Cambridge AS & A Level Psychology 9990 Study Notes (2024-2026)

The biological core study on REM sleep and dreaming. This note builds the science of sleep (stages, EEG wave types, biological rhythms), then drills the three hypotheses, the EEG/EOG procedure, the exact results, and how to evaluate the study in context for full Paper 1 marks.

What you’ll learn

Mapped to the Cambridge International A Level 9990 syllabus (2024-2026).

Outline the psychology being investigated: sleep, dreaming and ultradian rhythms.
Describe the science of sleep — sleep stages, EEG wave types and biological rhythms — that underpins the study.
Describe the background, aim(s) and the three hypotheses of Dement & Kleitman (1957).
Describe the procedure, including use of EEG/EOG, the controlled lab method and how participants were woken and questioned.
Describe the results and the conclusions drawn about REM sleep and dreaming.
Evaluate the study (methodology, ethics, strengths/weaknesses) and relate it to issues and debates.

The science of sleep (background substance)

Sleep moves through stages with distinct EEG patterns; REM is 'paradoxical sleep'; the cycle is an ultradian rhythm.

Before the study makes sense, understand what sleep actually is — this is the substance most textbooks skim, and knowing it lets you explain the study rather than just recite it.

Sleep happens in stages, repeated in cycles. Across the night you pass through stages of non-REM (nREM) sleep and periods of REM (rapid eye movement) sleep. One full cycle lasts roughly 90 minutes and repeats about 4–6 times a night, with REM periods getting longer towards morning.

Each stage has a distinct brain-wave (EEG) signature:

State	EEG pattern	What's happening
Awake, alert	Beta waves (fast, low amplitude)	Active thinking
Awake, relaxed (eyes closed)	Alpha waves	Calm, drowsy
Light sleep (nREM 1–2)	Theta waves	Drifting off
Deep sleep (nREM 3–4)	Delta waves (slow, large)	'Slow-wave' restorative sleep
REM	Fast, low-voltage, awake-like ('sawtooth')	Vivid dreaming; rapid eye movements; body muscles relaxed/paralysed

REM is called 'paradoxical sleep' because the brain looks awake on the EEG even though the person is deeply asleep and hard to wake — a paradox. This is exactly why an EEG can be used to detect REM and so 'catch' dreaming as it happens.

Biological rhythms. The sleep–wake cycle (~24 hours) is a circadian rhythm; the ~90-minute cycle of sleep stages within a night is an ultradian rhythm (a rhythm shorter than 24 hours). These rhythms are largely innate/biological — which is why this study sits in the biological approach and supports the nature side of the debate.

Sleep = repeating ~90-min cycles of nREM + REM (an ultradian rhythm).
EEG waves: beta (awake) → alpha (relaxed) → theta (light) → delta (deep) → REM (awake-like).
REM = 'paradoxical sleep': awake-like brain, asleep body, vivid dreams.
EEG can detect REM, so dreaming can be 'caught' as it happens.
Sleep rhythms are innate/biological → nature.

Psychology investigated, background and aim

An objective way to study dreaming — by linking dreams to measurable REM sleep.

Psychology being investigated: sleep, dreaming and ultradian rhythms.

Background. Dreaming had previously been studied only by asking people what they remembered in the morning — unreliable and subjective (memory fades fast, and you cannot check the report against anything). Earlier work (Aserinsky & Kleitman) had discovered REM sleep. Dement & Kleitman wanted an objective, scientific way to study dreaming by tying it to physiological measures recorded as they happened.

Aim. To investigate the relationship between eye movements and dreaming, by testing three specific predictions:

Dreaming occurs during REM sleep, not non-REM (nREM) sleep.
There is a positive correlation between the length of REM sleep and the dreamer's estimate of how long they had been dreaming (i.e. dreams happen in real time).
The direction/pattern of eye movements corresponds to the content of the dream — the 'scanning hypothesis'.

Topic: sleep, dreaming, ultradian rhythm (~90-min cycle).
Problem with old research: dream reports were subjective/unreliable.
Aim = make dream research OBJECTIVE by linking it to REM.
Three hypotheses: REM↔dreaming; REM length↔dream length; eye direction↔dream content.

Procedure and methodology

Controlled sleep lab, EEG + EOG, participants woken in REM or nREM and asked about dreams.

Participants: 9 adults (7 male, 2 female). 5 were studied in detail; the other 4 were used only to confirm the findings.

Controls (this is a controlled laboratory study):

Participants reported to the lab before their normal bedtime and slept in a quiet, dark room.
They avoided caffeine and alcohol on test days (both alter sleep architecture, especially REM).
An EEG recorded brain-wave activity (to identify the sleep stage) and an EOG recorded eye movements via electrodes placed near the eyes.

Waking procedure: participants were woken at various times by a doorbell and immediately spoke a dream report into a recorder near the bed — they had no contact with the experimenter (to avoid cues/bias). They were not told whether they had been woken from REM or nREM, so they could not guess the 'expected' answer.

The three tests:

REM vs nREM dreaming: participants were woken in REM or nREM and asked whether they had been dreaming and to describe it. Some were woken in a random sequence; others (with one participant) deliberately misled by the experimenter to check honesty — recall still tracked REM.
Duration estimation: participants were woken after either 5 or 15 minutes of REM and asked to judge which length they had been dreaming for.
Eye movements vs content: eye-movement patterns (vertical, horizontal, mixed, little/none) were recorded before waking and compared with the reported dream content.

9 participants (7 M, 2 F); 5 studied intensively.
EEG = brain waves (sleep stage); EOG = eye movements.
Controls: no caffeine/alcohol; woken by doorbell; report into recorder (no experimenter contact); not told the sleep stage.
Test 1: REM vs nREM dreaming; Test 2: 5 vs 15 min estimation; Test 3: eye direction vs content.

Results (with the numbers)

REM strongly linked to dreaming; accurate duration estimates; eye movements matched content.

Test 1 — REM vs nREM. Dreams were reported far more often when woken in REM than nREM:

REM awakenings: dream recalled in about 80% of cases (152 of 191).
nREM awakenings: dream recalled in only about 7% of cases (11 of 160) — and these were usually vague 'feelings' rather than detailed narratives.
The few nREM 'dreams' often came soon after the end of a REM period (i.e. carried over).

Test 2 — Duration estimation. Participants were usually accurate at judging whether they had been dreaming for 5 or 15 minutes (correct on the large majority of trials). There was also a positive correlation between the length of REM and the number of words in the dream narrative — the longer the REM, the longer/more detailed the dream — supporting real-time dreaming.

Test 3 — Eye movements and content. The direction of eye movements often matched the dream:

Vertical eye movements → e.g. a dream of looking up and down (such as climbing).
Horizontal eye movements → e.g. watching something move from side to side.
Mixed / little movement → looking at nearby or distant fixed objects.

This supports the scanning hypothesis: the eyes move as if the sleeper is 'watching' the dream.

REM dream recall ≈ 80% (152/191); nREM ≈ 7% (11/160).
Participants accurately estimated 5 vs 15 minute dreams.
Positive correlation: REM length ↔ words in dream report (real-time dreaming).
Eye-movement direction matched dream content (scanning hypothesis).

Conclusions

Dreaming is a REM phenomenon, occurs in real time, and can be studied objectively.

Dreaming occurs predominantly during REM sleep, so REM provides an objective, physiological indicator of dreaming.
Dreams appear to occur in real time (the length of REM matches the estimated/described length of the dream).
The pattern of eye movements relates to dream content, suggesting the sleeper is, in a sense, 'watching' the dream.
Overall, dreaming can be studied scientifically by measuring REM rather than relying on unreliable morning recall — a turning point that founded the whole field of sleep science.

Dreaming = a REM event → REM is an objective marker of dreaming.
Dreams happen in real time.
Eye movements relate to dream content.
Dream research can be made objective and scientific.

Evaluation — strengths, weaknesses, issues & debates

High control + objective data, but a small biased sample and questionable ecological validity.

Use these IN CONTEXT for Section B. Pick two strengths and two weaknesses, and include any named issue.

Strengths

High control / standardisation (lab, no caffeine/alcohol, doorbell waking, no experimenter contact, EEG/EOG). This makes the study replicable and the data reliable.
Objective, quantitative data from EEG/EOG (not just self-report), reducing researcher bias and increasing validity. Combining objective recordings with the dreamer's own report is a strong mixed-methods design.
Real-world application: founded sleep science and the diagnosis/treatment of sleep disorders (insomnia, sleep apnoea, narcolepsy).

Weaknesses

Small, biased sample (only 9 people, mostly male; just 5 studied in detail), so generalisability is limited — sleep can differ by age and sex.
Low ecological validity — sleeping in a lab wired to electrodes is not normal and may disrupt natural sleep (the 'first-night effect').
Reliance on self-report for dream content (Test 3) is subjective and could be affected by forgetting or interpretation.

Issues & debates

Nature vs nurture: the REM/sleep cycle is a biological, innate ultradian rhythm (nature).
Application to everyday life: sleep research, diagnosis of insomnia and other sleep disorders.
Individual vs situational: focuses on the individual's biology (brain activity).

Strength: high control → replicable + reliable.
Strength: objective EEG/EOG data → valid, low bias (mixed methods).
Weakness: tiny biased sample (9, mostly male) → poor generalisability.
Weakness: low ecological validity (lab + electrodes disrupt natural sleep).
Debates: nature (innate rhythm), application (sleep clinics).

How it’s examined

Paper 1 Section A: short-answer recall (e.g. 'state one control', 'describe how dream content was measured', 'outline one result'). Section B: describe the procedure (~6 marks) and evaluate (8–10 marks), often with a named issue such as ecological validity, generalisations or use of quantitative data. Examiner guidance: quote specific evidence (the ≈80%/≈7% figures, the no-contact control) and keep evaluation in context.

Sources: Cambridge International AS & A Level Psychology 9990 syllabus (2024-2026); Dement, W. & Kleitman, N. (1957) Journal of Experimental Psychology, 53(5): 339-46; 9990 Learner Guide & Scheme of Work (for examination from 2024); 9990 Specimen / past Paper 1 and mark schemes. Last reviewed 2026-05-21.

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Step-by-step worked examples — Dement & Kleitman (Sleep and Dreams)

Step-by-step solutions to past-paper-style questions on dement & kleitman (sleep and dreams), written exactly the way a tutor would explain them at the board.

1What did the EEG and EOG measure? (2 marks)
Getting started• procedure, AO1
Question
In Dement & Kleitman's study, state what was measured by (a) the EEG and (b) the EOG. (2 marks)
Step-by-step solution
1. Step 1
  (a) EEG measured brain-wave activity, used to identify the stage of sleep (including REM).
2. Step 2
  (b) EOG measured eye movements (via electrodes placed near the eyes).
Answer
(a) EEG = brain-wave activity / sleep stage; (b) EOG = eye movements. (2)
Examiner tip
1 mark each. A common slip is swapping them — EEG = brain, EOG = eyes (the 'O' is for oculo / eye).
2Outline one hypothesis (2 marks)
Getting started• aim, hypotheses, AO1
Question
Outline one of the hypotheses tested by Dement & Kleitman. (2 marks)
Step-by-step solution
1. Step 1
  Choose one of the three, e.g. 'There is a relationship between REM sleep and dreaming.'
2. Step 2
  Add precision: 'Participants will report dreaming when woken in REM, but not (or rarely) when woken in nREM.'
Answer
Dreaming occurs in REM sleep: participants will report dreams when woken in REM but rarely in nREM. (2)
Examiner tip
Other acceptable hypotheses: REM length correlates with estimated dream length; eye-movement direction matches dream content. Any one, stated clearly, gains both marks.
3Describe the duration-estimation test (4 marks)
Building confidence• procedure, AO1, AO2
Question
Describe how Dement & Kleitman tested whether people can judge the length of their dreams. (4 marks)
Step-by-step solution
1. Step 1
  Participants were woken after either 5 or 15 minutes of REM sleep.
2. Step 2
  They were asked to estimate whether they had been dreaming for 5 or 15 minutes.
3. Step 3
  Their estimates were compared with the actual REM time recorded by the EEG/EOG.
4. Step 4
  The number of words in each dream report was also correlated with the length of REM, to test 'real-time' dreaming.
Answer
Woken after 5 or 15 min of REM; asked to judge which; estimates compared to actual REM time; words in dream report correlated with REM length. (4)
Examiner tip
The '5 or 15 minutes' detail is the key markable fact. Adding the word-count correlation shows fuller knowledge.
4Outline the REM vs nREM results (4 marks)
Building confidence• results, AO1
Question
Outline the results Dement & Kleitman found when participants were woken in REM compared with nREM sleep. (4 marks)
Step-by-step solution
1. Step 1
  When woken in REM, participants recalled a dream in about 80% of cases (152/191).
2. Step 2
  When woken in nREM, participants recalled a dream in only about 7% of cases (11/160).
3. Step 3
  nREM 'dreams' were often vague feelings rather than detailed narratives.
4. Step 4
  This shows a strong association between REM and dreaming.
Answer
REM dream recall ≈ 80%; nREM ≈ 7% (often vague). Strong link between REM and dreaming. (4)
Examiner tip
Quote the figures (≈80% vs ≈7%). Precise quantitative results push describe answers into the top band.
5Describe the procedure (6 marks)
Stretch• procedure, AO1, Paper 1
Question
Describe the procedure of Dement & Kleitman's study of sleep and dreaming. (6 marks)
Step-by-step solution
1. Step 1
  Sample/setup: 9 adults (7 male, 2 female; 5 studied in detail) slept in a controlled sleep laboratory.
2. Step 2
  Controls: they avoided caffeine and alcohol; an EEG recorded brain waves and an EOG recorded eye movements.
3. Step 3
  Waking: participants were woken by a doorbell at various times and spoke a dream report into a recorder — with no contact with the experimenter (to avoid bias).
4. Step 4
  Test 1 (REM vs nREM): woken in REM or nREM and asked whether they had been dreaming.
5. Step 5
  Test 2 (duration): woken after 5 or 15 min of REM and asked to estimate the length.
6. Step 6
  Test 3 (content): eye-movement patterns (vertical/horizontal/mixed) were recorded and compared with the reported dream content.
Answer
9 adults in a sleep lab; no caffeine/alcohol; EEG + EOG; woken by doorbell, report into recorder (no experimenter contact); three tests — REM vs nREM dreaming, 5/15-min duration estimation, eye-movement direction vs dream content. (6)
Examiner tip
Top band needs breadth (sample, controls, all three tests). The 'no experimenter contact' control is a great extra detail that also fuels evaluation.
6Evaluate — one weakness about ecological validity (4 marks)
Stretch• evaluation, AO3, ecological-validity, exam-technique
Question
Evaluate Dement & Kleitman's study by explaining one weakness to do with ecological validity. (4 marks)
Step-by-step solution
1. Step 1
  Point. The study has low ecological validity.
2. Step 2
  Explain. It took place in an artificial sleep laboratory, which is not how people normally sleep.
3. Step 3
  Evidence (in context). Participants were wired to an EEG and EOG and woken repeatedly by a doorbell.
4. Step 4
  Link. This could disrupt natural sleep and dreaming, so the behaviour recorded may not reflect normal sleep at home — though the basic REM cycle is physiological and likely still occurs.
Answer
Low ecological validity: sleeping wired to electrodes in a lab and woken by a doorbell is unnatural and may disrupt normal sleep — but the REM cycle is physiological, so core findings likely hold. (4)
Examiner tip
The counter-balancing final clause (REM is physiological, so findings are robust) earns extra AO3 credit for a reasoned, two-sided point.

Model Answers — Dement & Kleitman (Sleep and Dreams)

High-scoring sample answers for dement & kleitman (sleep and dreams) on the Cambridge International A Level 9990 paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.

Question 1
9990 Paper 1 Section B (describe) style6 marks
Q (6 marks). Describe how Dement & Kleitman investigated the relationship between eye movements and dreaming.
Model answer
Dement & Kleitman studied 9 adults (7 male, 2 female) in a controlled sleep laboratory, recording brain activity with an EEG and eye movements with an EOG. Participants avoided caffeine and alcohol and slept overnight in the lab.

To investigate the link between eye movements and dreaming, participants were woken at different times by a doorbell and immediately described their dream into a recorder, with no contact with the experimenter. In one test, the direction of eye movements recorded just before waking was compared with the content of the dream that was reported. For example, mainly vertical eye movements were associated with dreams of looking up and down (such as climbing), horizontal movements with watching something move from side to side, and little/mixed movement with looking at nearby or fixed objects.

This allowed Dement & Kleitman to test the 'scanning hypothesis' — the idea that the eyes move as if the sleeper is watching the events of the dream.
Why this scores
Why this scores well. It covers sample, apparatus (EEG/EOG), controls, the waking method, and — crucially — the specific link between eye-movement direction and dream content with examples. Examiners reward precise procedural detail over a vague summary.
Question 2
9990 Paper 1 Section B (evaluate) style10 marks
Q (10 marks). Evaluate the study by Dement & Kleitman in terms of two strengths and two weaknesses. At least one of your evaluation points must be about generalisations.
Model answer
Strength 1 — high control and standardisation. The study was a controlled laboratory experiment: participants avoided caffeine and alcohol, were woken by a standard doorbell, and reported dreams with no contact with the experimenter. These controls reduce confounding variables and demand characteristics, making the study replicable and the data reliable.

Strength 2 — objective, quantitative data. Brain activity and eye movements were measured with an EEG and EOG rather than relying only on what people remembered. This objective evidence (e.g. dream recall of about 80% in REM versus about 7% in nREM) is not easily distorted by bias, increasing the validity of the conclusion that dreaming is linked to REM.

Weakness 1 — generalisations (named issue). The sample was very small and biased — only 9 participants, most of them male, with just 5 studied in detail. Such a small, male-dominated sample may not represent the wider population, so the findings about REM and dreaming may not generalise to women, children or older adults whose sleep patterns can differ.

Weakness 2 — low ecological validity. Sleeping while wired to an EEG and EOG in a laboratory, and being woken repeatedly by a doorbell, is very different from sleeping normally at home. This artificial setting could disrupt natural sleep and dreaming, so the behaviour recorded may not reflect everyday sleep. (However, because the REM cycle is physiological, the core link between REM and dreaming is likely to be robust.)

Conclusion. The study's tight control and objective measures make its central finding convincing, but its tiny, biased sample limits how widely the results can be generalised.
Why this scores
Why this reaches the top band. Exactly two strengths and two weaknesses, the named issue (generalisations) is included and explained with specific evidence ('9 participants, mostly male'), every point is in context (PEEL), and there is a reasoned conclusion (AO3). The bracketed counter-point on ecological validity shows balanced argument.
Question 3
9990 Paper 1 Section B (describe) style6 marks
Q (6 marks). Describe the results of Dement & Kleitman's study of sleep and dreaming.
Model answer
Dement & Kleitman found a strong link between REM sleep and dreaming. When participants were woken during REM, they reported a dream in about 80% of cases (152 of 191 awakenings). When woken during non-REM (nREM) sleep, they reported a dream in only about 7% of cases (11 of 160), and these were usually vague impressions rather than detailed dreams.

For dream duration, participants woken after either 5 or 15 minutes of REM were usually accurate in judging which length they had been dreaming for. There was also a positive correlation between the length of REM and the number of words in the dream report — longer REM periods produced longer dreams — suggesting dreams happen in real time.

Finally, the direction of eye movements tended to match the content of the dream: for example, vertical eye movements were linked to dreams of looking up and down, and horizontal movements to watching something move from side to side. This supported the 'scanning hypothesis'.
Why this scores
Why this scores well. All three sets of results are covered with specific figures (≈80% vs ≈7%; 152/191 vs 11/160; 5/15 minutes) and the eye-movement examples. Quoting numbers is exactly what pushes a describe answer into the top band.
Question 4
9990 Paper 1 Section B (methodology) style8 marks
Q (8 marks). Evaluate the use of the laboratory experiment as a method in Dement & Kleitman's study.
Model answer
Strength 1 — high control and standardisation. Because it was a laboratory study, Dement & Kleitman could control many variables: participants avoided caffeine and alcohol, were woken by a standard doorbell, and reported dreams with no contact with the experimenter. This control reduces confounding variables and demand characteristics, and means the study can be replicated to check its reliability.

Strength 2 — objective, quantitative measurement. The lab allowed the use of an EEG and EOG to record brain activity and eye movements directly. These objective data (e.g. dream recall of ≈80% in REM vs ≈7% in nREM) do not depend on opinion, increasing the validity of the conclusion that dreaming is linked to REM.

Weakness 1 — low ecological validity. A laboratory is not where people normally sleep. Being wired to electrodes and woken repeatedly by a doorbell is unnatural and may disrupt normal sleep (the 'first-night effect'), so the dreaming recorded may not reflect everyday sleep at home.

Weakness 2 — reliance on self-report for content. Although REM was measured objectively, the content of dreams (Test 3) still came from the participants' own reports, which are subjective and vulnerable to forgetting or interpretation — so part of the data is less controlled than the brain measures.

Conclusion. The laboratory method gave the study its great strengths — control and objective measurement — which is why its core findings are trusted. Its main cost is ecological validity, though because REM is physiological it likely occurs in the lab much as it does at home, so the central conclusion is probably robust.
Why this scores
Why this reaches the top band. Two strengths and two weaknesses, all tied to the laboratory method specifically and in context (caffeine control, EEG/EOG, doorbell), with a balanced conclusion (AO3). Note how each point names a real feature of this study rather than a generic 'labs are artificial'.

Key Definitions and Keywords — Dement & Kleitman (Sleep and Dreams)

Definitions to memorise and the exact keywords mark schemes credit for dement & kleitman (sleep and dreams) answers — sharpened from recent examiner reports for the 2026 Cambridge International A Level 9990 sitting.

REM sleep
Examiner keyword
Rapid eye movement sleep — a stage of sleep with fast eye movements, brain activity similar to being awake, and the most vivid dreaming.
nREM sleep
Examiner keyword
Non-rapid-eye-movement sleep — the deeper stages of sleep with little eye movement and little/no detailed dreaming.
EEG (electroencephalogram)
Examiner keyword
A device that records electrical brain-wave activity, used here to identify the stage of sleep.
EOG (electro-oculogram)
Examiner keyword
A device that records eye movements using electrodes placed near the eyes.
Ultradian rhythm
Examiner keyword
A biological rhythm shorter than 24 hours — here, the cycle of sleep stages that repeats roughly every 90 minutes.
Scanning hypothesis
The idea that the direction of eye movements during REM corresponds to what the sleeper is 'watching' in the dream.
Objective data
Data measured directly (e.g. by a machine) without relying on opinion, reducing bias — e.g. the EEG/EOG recordings.
Ecological validity
The extent to which findings reflect real, everyday behaviour. Sleeping in a wired-up lab lowers it here.

Common Mistakes and Misconceptions — Dement & Kleitman (Sleep and Dreams)

The traps other students keep falling into on dement & kleitman (sleep and dreams) questions — taken from recent Cambridge International A Level 9990 examiner reports and mark schemes — and how to avoid them.

✕Swapping EEG and EOG (saying EEG measures eye movements)
9990 mark schemes
Why it happens
The abbreviations look similar.
How to avoid it
EEG = brain (E for encephalo). EOG = eyes (O for oculo). Memorise the 'O = eye' link.
✕Knowing only 'REM = dreaming' and missing the other two hypotheses
Why it happens
Students learn the headline finding only.
How to avoid it
Learn all three: (1) REM↔dreaming; (2) REM length↔estimated dream length; (3) eye direction↔dream content.
✕Describing results without any figures
Why it happens
Students remember the trend but not the numbers.
How to avoid it
Quote ≈80% (REM) vs ≈7% (nREM) and '5 or 15 minutes' for the duration test — these are markable facts.
✕Generic evaluation ('small sample') without saying who was in it
9990 Learner Guide example responses
Why it happens
Stock evaluation phrases.
How to avoid it
Be specific: '9 participants, mostly male, only 5 studied in detail' → poor generalisability. Specific + explained = top band.
✕Claiming REM 'causes' dreaming with certainty from the correlational parts
Why it happens
Confusing the experimental and correlational elements.
How to avoid it
Tests 2 and 3 are correlational — they show relationships, not cause. Phrase carefully: REM is 'strongly associated with' dreaming.

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Dement & Kleitman (Sleep and Dreams)

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Short Study Notes — Dement & Kleitman (Sleep and Dreams)

Detailed Notes

What you’ll learn

How it’s examined

1What did the EEG and EOG measure? (2 marks)

2Outline one hypothesis (2 marks)

3Describe the duration-estimation test (4 marks)

4Outline the REM vs nREM results (4 marks)

5Describe the procedure (6 marks)

6Evaluate — one weakness about ecological validity (4 marks)

REM sleep

nREM sleep

EEG (electroencephalogram)

EOG (electro-oculogram)

Ultradian rhythm

Scanning hypothesis

Objective data

Ecological validity

✕Swapping EEG and EOG (saying EEG measures eye movements)

✕Knowing only 'REM = dreaming' and missing the other two hypotheses

✕Describing results without any figures

✕Generic evaluation ('small sample') without saying who was in it

✕Claiming REM 'causes' dreaming with certainty from the correlational parts

Practice questions

Past paper style quiz

Assess your understanding