Main assumptions of the biological approach

The biological approach in psychology focuses on how physical and biological factors influence our thoughts, feelings, and actions. This perspective views the mind and body as interconnected, with behaviour emerging from processes in the brain and body.

Key assumptions

• Biological basis of behaviour - Behaviours, thoughts (cognitions), and emotions can be explained through the functioning of the brain, the influence of hormones, genetics, and evolution.
• Understanding similarities and differences - Commonalities and variations between people arise from biological factors, but these interact with other influences such as environmental, social, and cultural elements.

This approach does not dismiss non-biological factors but prioritises biological explanations while recognising their interplay with external influences.

Understanding sleep and its stages

Sleep is a natural state where the body becomes inactive and conscious awareness is temporarily suspended. It plays a vital role in rest, repair, and cognitive processing. Scientists identify distinct sleep stages based on brain activity, which can be measured using specialised tools.

Measuring brain activity during sleep

Electroencephalography (EEG) is a technique that records electrical activity in the brain through electrodes placed on the scalp. It produces readings of brain waves, showing patterns of amplitude and frequency. These EEG readings help distinguish between different sleep stages, revealing how brain activity changes throughout the night.

The five stages of sleep

Sleep progresses through cycles, each lasting about 90 minutes, with varying brain-wave patterns.

These stages are:

1. Stage 1 NREM (non-rapid eye movement) - Light sleep where it's easy to wake up; characterised by low-amplitude, high-frequency theta waves.
2. Stage 2 NREM - Still light sleep, but slightly deeper; features theta waves with occasional sleep spindles and K-complexes.
3. Stages 3 and 4 NREM - Deep sleep that's harder to wake from; marked by high-amplitude, low-frequency delta waves; important for physical restoration.
4. REM (rapid eye movement) sleep - Brain waves show low amplitude and high frequency, similar to being awake; eyes move quickly under closed lids, but other muscles are temporarily paralysed to prevent acting out dreams; this stage is strongly associated with vivid dreaming.

Earlier sleep cycles have more deep NREM sleep, while later cycles include more time in stages 1, 2, and REM.

Ultradian rhythms and dreams

Bodily functions follow various cycles, some of which occur multiple times within a day. These rhythms help regulate essential processes like sleep.

Ultradian rhythms

• Ultradian rhythms are biological cycles that repeat more than once every 24 hours, such as the 90-minute sleep cycles that occur during a night's rest.
• During these cycles, the body alternates between NREM sleep (stages 1-4) and REM sleep.
• As the night progresses, cycles shift to include a higher proportion of REM sleep.

Dreams

• Dreams are subjective experiences or memories recalled from sleep, often involving stories, images, or emotions.
• Research shows dreams are more commonly reported during REM sleep than NREM, suggesting a link between brain activity and dream occurrence.

Background to Dement and Kleitman's study

Early research on sleep laid the foundation for investigating dreams scientifically. Nathaniel Kleitman, a pioneer in sleep studies, used family members as participants in his work over many years.

In 1953, Kleitman's student Eugene Aserinsky employed EEG to differentiate REM from NREM sleep. They discovered that people awakened during REM were more likely to recall dreams compared to those in NREM.

Building on this, William Dement and Kleitman sought a reliable, objective method to detect dreaming. They aimed to use biological measures like EEG readings rather than relying solely on subjective verbal reports, which could be biased or inaccurate.

Aims of Dement and Kleitman's study

The study focused on establishing clear links between measurable brain activity and dreaming.

Specifically, it investigated:

1. Whether dream recall occurs more frequently in REM sleep than in NREM sleep.
2. Whether participants can accurately judge how long their dreams lasted.
3. Whether the direction of eye movements (vertical or horizontal) during REM matches the content of reported dreams.
4. Whether there's a correlation between the length of a REM episode and the word count in dream descriptions.

Methodology of Dement and Kleitman's study

This research was conducted as a laboratory experiment to ensure controlled conditions for measuring sleep and dreams.

Research design and methods

• Type of study - Laboratory experiment using a repeated measures design for aims 1-3, and a correlational analysis for aim 4.
• Data collection - Combined self-reports with objective EEG measurements, followed by interviews for detailed dream narratives.

Variables

• Independent variables (manipulated by researchers):
  • Waking participants during REM or NREM sleep.
  • Waking after 5 or 15 minutes of REM sleep.
  • Waking after REM with specific eye movement patterns: mainly vertical, mainly horizontal, mixed, or limited.
• Dependent variables (measured outcomes):
  • Whether a dream was reported (quantitative: yes/no, with detailed description required).
  • Perceived duration of dream (initially in minutes, later as a choice between 5 or 15 minutes; quantitative).
  • Dream content description (qualitative: narrative details) and word count (quantitative).

Participants

• Sample size and demographics - Nine adults (seven men, two women) from Chicago, USA; five were studied in depth, with four used to verify findings.
• Sampling technique - Not specified in the original report.

Procedure of Dement and Kleitman's study

The study took place in a controlled sleep laboratory at the University of Chicago to minimise external influences.

Key steps

1. Participants arrived at their normal bedtime, having avoided alcohol and caffeine that day.
2. They slept in a quiet, dark room with electrodes attached near their eyes and on the scalp; wires were bundled to prevent tangling.
3. EEG equipment in an adjacent room monitored brain waves and eye movements.
4. Researchers woke participants multiple times per night using a loud doorbell, based on EEG data and timers.
5. Upon waking, participants recorded self-reports of dreams using a bedside device; researchers sometimes entered for follow-up interviews without revealing sleep stage or eye movement details.

Controls for reliability

• Standardised electrode placement (2-3 near eyes and on scalp).
• Consistent waking method (same doorbell for all).
• Uniform instructions and abstention from stimulants.

Ethical considerations

• Confidentiality - Participants identified only by initials; dream details not linked to names.
• Privacy - Sensitive information handled discreetly to protect participants.

Results of Dement and Kleitman's study

The findings provided quantitative evidence linking REM sleep to dreaming. REM never started right after falling asleep, occurring every 92 minutes on average (range: 70-104 minutes), with episodes lasting about 20 minutes (range: 3-50 minutes) and lengthening later at night.

Dream reporting by sleep stage

Accuracy of dream duration estimates

One participant (DN) showed lower accuracy of only 65 per cent, often underestimating, and was only correct 50 per cent of the time when woken after 15 minutes.

Eye movements and dream content

Correlation between REM duration and dream narrative

Correlation coefficients ranged from +0.40 to +0.71 across participants, averaging +0.58.

Conclusions of Dement and Kleitman's study

The study demonstrated clear connections between biological markers and dreaming:

• Dream reports are far more common in REM than NREM sleep.
• Dreams unfold in real time, with estimated durations matching actual REM lengths.
• Eye movements during REM correspond to dream actions, suggesting they are not random.
• Objective EEG measures of REM can reliably indicate dreaming, reducing reliance on subjective reports.

These findings highlight how biological processes underpin sleep experiences.

Evaluation of Dement and Kleitman's study

Strengths

• Reliability - Standardised procedures (e.g., consistent doorbell for waking, electrode placement) allow replication to check consistency.
• Objectivity - Quantitative EEG data (e.g., wave amplitude and frequency) minimised researcher bias in classifying sleep stages.

Weaknesses

• Validity - Some data was discarded as recordings were too muffled and dreams could not be accurately transcribed.
• Generalisability - Small sample (nine participants, mostly men, from one US city) limits applicability to broader populations; ages and occupations were not provided so individual differences may have affected results.

Issues and debates in the biological approach

The biological approach raises broader questions about human behaviour, with Dement and Kleitman's study providing relevant examples.

Application to everyday life

Insights into normal sleep patterns help identify atypical sleep or dreaming. This enables psychologists to offer targeted interventions, such as therapies or lifestyle changes, to enhance sleep quality and overall health.

Nature versus nurture

• Support for nature - Universal patterns like REM/NREM cycles and higher dream recall in REM across all participants suggest innate biological mechanisms that aid survival.
• Support for nurture - Varied dream content reflects personal experiences, showing how environment shapes what we dream; differences in REM duration may stem from lifestyle factors.