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A systematic distortion in how research is carried out, interpreted or reported.
Researcher bias
The researcher's expectations influence the behaviour of participants or the interpretation of data.
Participant bias
Participants change their behaviour, e.g. demand characteristics or social desirability.
Confirmation bias
Seeking or interpreting evidence in a way that supports existing beliefs.
Cultural bias
Assuming findings from one culture apply to all (e.g. WEIRD samples).
Bias can enter at every stage: choosing the question, sampling, the procedure, measuring, analysing and publishing (publication bias: positive results are more likely to be published).
Demand characteristics: cues that tell participants the aim, so they behave as they think is expected. Social desirability: answering in a way that looks good.
Much research uses WEIRD samples (Western, Educated, Industrialized, Rich, Democratic), so findings may not generalize to most of the world's population.
Controls: double-blind procedures, standardized instructions, deception (with debriefing), triangulation, reflexivity in qualitative research, and cross-cultural replication.
Cognitive biases (anchoring, confirmation bias) are also topics of study in their own right in the cognitive approach.
Worked example
Explain how bias may have affected a study in which participants rated their own stress levels after a stress-management course.
Participants knew the aim, so demand characteristics may lead them to report lower stress to please the researcher.
Social desirability may make them under-report stress.
A physiological measure (cortisol) or a control group with a placebo course would reduce the bias.
Exam tip: Name the specific type of bias, explain how it could change the results in that study, and suggest how it could be reduced.
C.2Causality
Key terms
Causality
A change in one variable directly produces a change in another.
Correlation
A relationship between two variables; it does not show cause.
Confounding variable
An uncontrolled variable that changes with the IV and could explain the result.
Bidirectional ambiguity
In a correlation, it is unclear which variable affects which.
Only a true experiment (IV manipulated, random allocation, controls) can establish cause and effect.
Correlational and quasi-experimental studies show relationships; a third variable may explain both.
Example: Maguire et al. (2000) found larger posterior hippocampi in taxi drivers, but a correlation alone cannot rule out that people with larger hippocampi become taxi drivers; the link with years of driving supports (but does not prove) plasticity. Draganski et al. (2004) used a longitudinal design to show change caused by learning to juggle.
In the biological approach, animal studies and drug studies can manipulate variables directly (e.g. blocking a neurotransmitter), making causal claims stronger, but generalization to humans is limited.
Reductionism: explaining complex behaviour by one cause (e.g. a single gene) ignores interactions between factors.
Worked example
A study finds that people who use social media more report lower mood. Explain why this does not show that social media causes low mood.
It is a correlation: the variables were measured, not manipulated.
Bidirectional ambiguity: low mood may lead people to use social media more.
A third variable (e.g. loneliness) could cause both. An experiment that randomly assigns people to reduce use would test causality.
Exam tip: Whenever a study is correlational or quasi-experimental, say clearly that causal conclusions cannot be drawn and why.
C.3Change
Key terms
Neuroplasticity
The brain's ability to change its structure and function in response to experience.
Development
Systematic change in behaviour and cognition across the lifespan.
Acculturation
Psychological and cultural change when people from different cultures come into contact.
Longitudinal study
Studies the same participants over time to measure change.
Change is studied at every level: neurons (synaptic pruning, dendritic branching), cognition (schemas updated by new experience), and culture (acculturation, globalization).
Longitudinal designs measure change directly; cross-sectional designs compare different groups at one time and can be confounded by cohort effects.
Behaviour change is a goal in health promotion, therapy and education: change can be measured as symptom reduction, behaviour frequency or test performance.
Change raises questions of stability: personality, attachment style and memory are partly stable, partly changeable.
Worked example
Describe how Draganski et al. (2004) provided evidence of change in the brain.
24 volunteers were scanned before learning to juggle, after three months of practice and three months after stopping.
Grey matter increased in areas processing visual motion (mid-temporal area) and decreased again when practice stopped.
The longitudinal design shows the brain changed because of learning: neuroplasticity.
Exam tip: When writing about change, identify what changed, what caused the change, and how the change was measured.
C.4Measurement
Key terms
Operationalization
Defining a variable precisely so it can be measured, e.g. 'stress' as cortisol level.
Reliability
Consistency of a measure: the same result under the same conditions.
Validity
Whether a measure assesses what it claims to measure.
Construct
An abstract concept that cannot be observed directly, such as intelligence or memory.
Psychology measures constructs indirectly: through behaviour, self-report, physiological indicators or brain imaging. Each has strengths and limits.
Reliability: test–retest, inter-rater (agreement between observers). Validity: internal (did the IV cause the DV?), external/ecological (does it generalize to real life?), construct (does the measure capture the concept?).
Brain imaging: MRI (structure), fMRI (activity via blood oxygen), PET (activity via radioactive tracer), EEG (electrical activity, excellent timing, poor localization).
Self-reports are cheap and access thoughts but are open to social desirability and memory errors.
Worked example
Explain why fMRI is useful but limited for studying memory.
fMRI shows which areas become more active during a memory task, with good spatial resolution and no radiation.
But it measures blood flow, an indirect sign of neural activity, with a delay of a few seconds (poor temporal resolution).
It shows correlation between activity and task, not that an area causes the function; the lab setting is also artificial.
Exam tip: Always show how the researchers operationalized the IV and DV in any study you describe; it is an easy way to show precise knowledge.
C.5Perspective
Key terms
Biological approach
Explains behaviour through the brain, neurotransmitters, hormones and genes.
Cognitive approach
Explains behaviour through mental processes: memory, thinking, perception, decision-making.
Sociocultural approach
Explains behaviour through social interaction, groups and culture.
Holism
Explaining behaviour by considering several interacting levels at once.
The same behaviour can be explained at different levels: depression as low serotonin (biological), negative thinking patterns (cognitive) or stressful life events and social support (sociocultural).
The biopsychosocial model combines the three, which explains complex behaviour better but is harder to test.
Perspective also means the viewpoint of researchers and participants: emic (from inside a culture) vs etic (from outside, seeking universals).
Evaluating with perspectives: compare explanations, show what each misses, and show where they interact (e.g. Caspi et al., 2003: genes × stressful events).
Worked example
Explain depression from two different perspectives.
Biological: lower serotonin activity is linked to depression; SSRIs that increase serotonin can reduce symptoms.
Cognitive: Beck proposed a negative cognitive triad (negative views of self, world and future); CBT challenges these thoughts.
Neither alone explains why only some people at genetic risk become depressed; stressful life events (sociocultural) also matter.
Exam tip: Comparing two approaches on the same behaviour is one of the quickest ways to show critical thinking.
C.6Responsibility
Key terms
Informed consent
Participants agree after being told what the study involves and their rights.
Right to withdraw
Participants can leave at any time, and remove their data.
Debriefing
Explaining the true aim afterwards, especially after deception.
Confidentiality
Personal data are protected and participants are not identifiable.
Social responsibility
Considering how research findings are used and their effect on society.
Ethical guidelines (e.g. APA, BPS) require informed consent, protection from harm, the right to withdraw, confidentiality, debriefing, and justified, minimal deception.
Extra care is needed for vulnerable groups: children (parental consent), patients, and people in unequal power relationships.
Animal research follows the 3Rs: replace, reduce, refine; it must be justified by possible benefits.
Responsibility also concerns applications: how findings on genes, intelligence or culture are reported, so they do not reinforce stereotypes or discrimination.
Studies such as Milgram (1963) and Zimbardo (1971) would not be approved today because of stress and harm to participants.
Worked example
Discuss one ethical issue in Bandura's (1961) Bobo doll study.
Children aged 3–5 were exposed to an aggressive adult model and then frustrated, which may cause distress and teach aggressive behaviour (protection from harm).
Children could not give informed consent; parental consent was needed.
On the other hand, the study helped understanding of observational learning, which informed media guidelines: a cost–benefit judgement.
Exam tip: Link each ethical issue to what actually happened in the study rather than listing guidelines in general.