Compare methods of measuring stress
Compare heart-rate and fMRI recording, salivary cortisol, life-event and Type A questionnaires, and explain why converging measures are useful but imperfect.
Section Paper 4 · Specialist Options: Application and Research Methods
Original StudyForA teaching mapped to Cambridge 9990 Health Psychology sections 3.4.1–3.4.3, 2028–2030 Version 1. Example studies illustrate the syllabus and are not official Cambridge materials or mark schemes. This is psychology education, not stress diagnosis or treatment advice.
Before you begin
- This lesson covers Cambridge Psychology 9990 Health Psychology section 3.4.2. A measure is an indicator of part of the stress response; interpreting it requires attention to validity, reliability, timing and context.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which statement best describes Wang et al. (2005)?
What you will learn
- Heart-rate and brain-function/fMRI recording; Wang et al. (2005)
- Salivary-cortisol sampling; Evans and Wener (2007)
- Self-report measures, including Type A and Holmes–Rahe questionnaires
Stress can be measured through different indicators
Heart-rate recording is a biological measure of cardiac activity. It can provide repeated readings during a task, but heart rate also changes with movement, health, caffeine, time and other conditions. It is not a direct read-out of subjective stress.
Functional MRI (fMRI) records changes related to brain activity; Wang et al. (2005) used arterial spin-labelling perfusion MRI to measure cerebral blood-flow changes during a monitored mental-arithmetic stress task. Participants also gave stress and emotional-state ratings, heart rate was recorded, and salivary cortisol was sampled. The study found associations between task-related blood-flow changes and reported stress in some brain regions. It did not make a scan into a direct measure of a person’s full experience.
Biological indicators can be less dependent on a participant choosing a questionnaire response, but they still require interpretation. Each indicator operationalises a different part of the response, and equipment, timing and the task can affect results.
Evans and Wener combined cortisol, self-report and performance
Evans and Wener (2007) studied 139 urban train commuters during rush hour. They compared the density of the train car and the immediate seating density near each passenger, using self-report, salivary cortisol and performance aftereffects as stress indicators. Train-car density was inconsequential for the indicators in this study, while immediate seating density significantly affected all three.
Using several indicators allows comparison across subjective, biological and performance data. The naturalistic commute gave the study an everyday setting, but passengers were not randomly assigned to seat density, and the sample and journey context were specific. The pattern does not establish that close seating will affect every commuter in every setting.
Salivary cortisol is a biological sample measure, but levels vary with timing and other influences. A sample must be collected and interpreted consistently; it is not a stress label or diagnosis by itself.
Questionnaires provide standardised self-report
The Holmes–Rahe questionnaire asks respondents to report listed life events that receive assigned LCU weights. Friedman and Rosenman’s Type A assessment asks about behaviours associated with their pattern. Both can make responses easier to compare, while remaining self-report measures rather than direct physiological recordings.
Psychometric quality includes reliability and validity. Reliability asks whether a measure gives consistent results under suitable repeat conditions. Validity asks whether it measures the construct or outcome it is intended to measure. A consistent questionnaire may still miss appraisal or cultural meaning; a biologically measured outcome may be objective but still not valid for the whole construct of psychological stress.
Self-reports can be affected by recall, question wording, interpretation, social desirability and language. Standardisation supports comparison, but evidence should be matched to the question. Combining a questionnaire with heart-rate, cortisol, brain-function or performance measures can reveal where methods converge or differ; it does not automatically remove bias.
Sources for this lesson
- Cambridge International AS & A Level Psychology 9990 syllabus, 2028–2030
- Cambridge International AS & A Level Psychology 9990 Reference List, 2028–2030
- Wang et al. (2005), Perfusion functional MRI reveals cerebral blood flow pattern under psychological stress
- Evans and Wener (2007), Crowding and personal space invasion on the train
- Holmes and Rahe (1967), The Social Readjustment Rating Scale
- Rosenman et al. (1974), Prediction of clinical coronary heart disease by a test for the coronary-prone behavior pattern
Pause and explain
What does reliability describe in a questionnaire?
Worked example
A researcher asks whether a crowded commute is stressful and plans to use only a cortisol sample taken once after a journey. Improve the measurement plan.
Show the worked solution
- Keep the biological sample, but specify collection time and compare it with a suitable baseline or condition.
- Add a subjective measure of perceived stress and a clearly defined context measure such as immediate seating density.
- Explain why each indicator represents a different part of stress and identify confounding variables.
Answer Record salivary cortisol consistently at an appropriate baseline and post-journey time, while collecting a brief standardised self-report and a defined measure of immediate seating density. The indicators can be compared, but cortisol varies with timing and other conditions; a single sample is not a direct measure or diagnosis of stress.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A stress study records heart rate, takes salivary-cortisol samples and asks participants to rate perceived stress during a monitored task. Classify the measures and explain one benefit of using all three.
Give me a hint
Separate the biological indicators from the subjective rating, then consider convergence.
Compare my reasoning
- Heart rate and salivary cortisol are biological indicators; the rating is self-report.
- The measures reflect different parts or time courses of a stress response.
- If they change together, this can support a converging interpretation; disagreement can also reveal measurement differences.
- None alone is a complete measure or diagnosis of stress.
Heart rate and cortisol are biological measures, while the participant’s rating is subjective self-report. Their combination can show whether different indicators move together or diverge. They are not interchangeable and none alone captures the whole experience.
Look for these in your work
- Measures classified
- Convergence explained
- Limits stated
A student claims that Evans and Wener proved train crowding causes stress because cortisol and performance changed. Evaluate this conclusion.
Give me a hint
State the sample, compare the two density measures and identify the naturalistic design limit.
Compare my reasoning
- The study observed 139 urban rush-hour train commuters.
- Immediate seating density affected self-report, cortisol and performance aftereffects; overall train-car density did not in that study.
- The naturalistic evidence is relevant to everyday commuting, but seat density was not randomly assigned and other differences may matter.
- The findings do not prove a universal causal effect for all commuters or settings.
Evans and Wener found that immediate seating density, rather than overall train-car density, was associated with the three stress indicators in their sample of 139 commuters. The everyday setting is useful, but the observational comparison cannot exclude all alternative explanations or justify a universal claim.
Look for these in your work
- Sample and context stated
- Two density measures distinguished
- Causal and generalisation limits explained
Design a small study comparing whether learners report different stress levels before and after a timed practice test. Include one self-report and one biological measure, then explain how you would protect validity.
Give me a hint
Use the same question timing and biological collection conditions at both points.
Compare my reasoning
- Use the same clearly worded stress-rating scale before and after the test, with a consistent time window.
- If using heart rate, record at rest for the same duration and posture at both points; note that movement and other factors can affect it.
- Keep the practice-test conditions consistent and obtain informed consent with a right to stop.
- Interpret ratings and heart rate as different indicators; a small class study cannot establish a health diagnosis or broad population pattern.
A repeated-measures design could collect a standardised stress rating and resting heart-rate reading before and after the same practice-test format. Use consistent timing, posture and instructions, obtain consent and note other factors such as movement. The two measures represent different indicators, and the class sample would limit generalisation.
Look for these in your work
- Two measures and operational timing stated
- A validity control included
- Ethical and generalisation limits stated
Common mistakes
- Calling heart rate or cortisol a complete objective measurement of stress
- Treating brain imaging as a direct picture of a person’s private experience
- Confusing a questionnaire’s reliability with its validity
- Ignoring sampling time, baseline, task and environmental influences on biological measures
- Claiming the Evans and Wener result applies to every crowded journey
What can you explain now?
Why can a reliable stress questionnaire still have limited validity?
Compare with the explanation
It may produce consistent scores while failing to capture the intended experience, overlooking appraisal or being unsuitable for a particular language or group.
Consistency concerns reliability; whether the measure captures the intended construct concerns validity.
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Make it stick
Compare one biological and one psychological measure of stress using the words reliability, validity and context.
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