IB Psychology SLTopic 6 — The Key ConceptsPaper 1 & 2Core idea~12 min read
The Six Key Concepts Explained
Six ideas run through the whole course, and both extended response questions are built on them. They are not extra content to learn. They are six questions you ask of anything psychology puts in front of you, and asking them is what turns describing into analysing.
📘 What you need to know
The six concepts are bias, causality, change, measurement, perspective and responsibility.
They apply across all three content areas and all four contexts.
They help you analyse, evaluate and connect psychological knowledge rather than describe it.
They are also Theory of Knowledge concepts, linking psychology to how knowledge is built generally.
They overlap. The same idea, such as reductionism, can belong to more than one.
You do not need all six in an answer. Three or four relevant ones is normally enough.
They are tools for thinking, not content to memorise.
The six at a glance
Stick this list on the inside of your folder. Running through six questions is a faster way into an unfamiliar study than trying to remember the right theory.
Bias
Bias is a limitation in objective thinking: information gets filtered through experience, expectation or preference. It can shape how research is designed and run, how data are interpreted, how theories are built, and how people judge things day to day. It may be explicit or completely unconscious, and careful design reduces it without ever removing it entirely.
Researcher and participant bias: demand characteristics, social desirability, expectations shaping data collection.
Sampling bias: opportunity or self-selected samples reducing representativeness and generalisability.
Confirmation and publication bias: favouring findings that support existing theory, and the greater chance of positive results being published, which distorts the evidence base.
Gender and cultural bias, including ethnocentrism, where findings from one group are wrongly applied to everyone.
Cognitive biases such as availability, anchoring and representativeness, which affect participants and researchers alike.
Reductionism and determinism, which can bias interpretation by underestimating human choice.
Causality
Causality is about establishing cause and effect between variables, and psychology finds it hard. Behaviour is usually driven by several interacting variables, relationships can run in both directions, and correlation never implies causation. Controlled methods are the main tool, but ethical and practical limits often cap how much control is possible.
The distinction between a statistical association and a real causal relationship.
Bidirectional ambiguity: A may cause B, B may cause A, or both may feed each other.
Control of extraneous and confounding variables through standardisation and random allocation.
Placebos, double-blind procedures and wait-list controls, which strip out expectancy effects.
Internal versus external validity: confident causal claims that may not travel beyond the setting.
Statistical significance versus effect size: a real effect can still be too small to matter.
Agency and motivation: human choice complicates any simple cause-and-effect story.
Change
Change is how behaviour develops, adapts or is altered over time. It can be gradual, as in development and maturation, or sudden, as in a shift in mood. It can be planned, through therapy or education, or unplanned, through illness or trauma. Behind all of it sits the free will and determinism debate.
Development and maturation: natural changes that happen without any intervention.
Biological and environmental determinism: what constrains or enables change in the first place.
Agency and motivation: readiness to change is often the strongest predictor of whether it happens.
Barriers and resistance: habits, stigma, social pressure, structural inequality, lack of resources.
Interventions and prevention at individual, community and population level.
Effectiveness of treatments: is the change meaningful, sustained, and better than doing nothing?
Longitudinal and repeated-measures designs, which separate short-term effects from lasting ones.
Measurement
Measurement is how psychologists observe, define and quantify behaviour. It is difficult because behaviour is often hard to see directly, depends on context, and has to be interpreted. Doing it well means operationalising variables clearly, choosing the right method, and checking reliability and validity. Using several kinds of evidence, or triangulating, raises credibility.
Choice of method: experiments, interviews, surveys, observations and case studies each measure different things.
Constructs versus variables: self-esteem and stress are abstract; the scales used to stand in for them are not.
Operationalisation: how a construct becomes something countable, and what that costs in validity.
Quantitative and qualitative data, and what each can and cannot show.
Self-reported, empirical and anecdotal data, and how much weight each deserves.
Direct versus indirect measures, including brain imaging and the assumptions in linking neural data to behaviour.
Type I and Type II errors: false positives and false negatives when interpreting results.
Prospective versus retrospective approaches, and the reliability of asking people to recall the past.
Perspective
A perspective is a particular way of understanding and explaining behaviour. The course uses three: biological, cognitive and sociocultural. Each rests on different assumptions, uses different methods, and produces different explanations. No single one explains behaviour fully, which is why a multi-perspective approach gives a more complete picture.
Theories and models shaping which questions get asked and which methods get used.
Reductionism and holism: breaking behaviour into parts versus considering interacting factors.
Emic and etic approaches: culture-specific understanding versus cross-cultural comparison.
Deductive and inductive reasoning: theory-driven hypothesis testing versus data-driven theory building.
Alternative explanations, and how tentative or revisable a conclusion should be.
Cultural and Indigenous perspectives, and the importance of cultural meaning in interpretation.
Responsibility
Responsibility covers the ethical and social obligations of psychologists in research and practice. Because psychologists work with people and sometimes animals, ethical standards exist to protect participants, minimise harm and maximise benefit. Ethics also shape research design and participant behaviour, so they affect validity too. And psychologists remain responsible for how findings are used once they are out in the world.
Informed consent and the right to withdraw without penalty.
Protection from harm, especially with sensitive topics or vulnerable groups.
Deception and debriefing: when deception can be justified, and the duty to explain afterwards.
Anonymity and confidentiality to prevent embarrassment, distress or social harm.
Cost-benefit analysis: weighing what the research gains against what it costs participants.
Animal and child participants, and the extra safeguards they require.
Socially sensitive research: avoiding reinforcing stereotypes, communicating carefully, and advocating for positive change.
Concepts overlap, and that is the point
There is no single correct way to apply these. If a study’s sampling problem also weakens its causal claim, say so — that is exactly the kind of connection the marks reward.
🧩 Four questions to ask of any topic you study
How was this knowledge built? What method produced it?
What assumptions sit underneath it? What is being taken for granted?
What limitations affect the findings? Sample, measure, setting, era.
How does it connect to other theories, approaches or contexts?
Practise this after every topic you finish. Spend five minutes asking which concepts it touches and what each would say about it. That habit is worth more before the exam than another pass of your notes.
Worked examples
WORKED EXAMPLE
Apply concepts to a familiar topic
You have just finished studying a theory that explains a disorder through brain chemistry. Which key concepts apply, and what would each say? [practice]
PerspectiveThis is a biological explanation, and it is reductionist: cognitive and sociocultural factors are left out.
Causality
Does the chemical difference cause the disorder, or result from it? Bidirectional ambiguity is live here.
Measurement
How was the chemistry measured, and how was the disorder defined and diagnosed?
Responsibility
A purely biological account can affect how people with the disorder are treated and viewed.
Four concepts, each with something specific to saynotice none of these required a new fact — only a new question
WORKED EXAMPLE
Show two concepts interacting
A treatment study reports large improvements in wellbeing after a six-week programme, measured by a self-report scale completed in front of the therapist. Link two concepts. [AO3]
Concept one: measurement
Wellbeing was operationalised as a self-report score, which is an indirect measure of an abstract construct.Concept two: bias
Completing it in front of the therapist invites social desirability bias and demand characteristics.
Now connect them
The measurement choice is what opens the door to the bias, so the two are not separate problems.
Then reach change and causality
Any apparent improvement may reflect how participants reported, not how they changed.
Measurement and bias compound each other herea fix worth naming: anonymous completion, collected by someone unconnected to the programme
💡 Exam tip
Define the concept before applying it, and apply it to the study rather than explaining it in isolation.
Three or four well-chosen concepts is normally enough. Six mentioned briefly is worse than two done properly.
Questions will not target a single narrow slice of a concept, so revise each one broadly rather than memorising one example.
Use the concepts as a checklist when you meet an unfamiliar study. They work as a reading tool, not just a writing tool.
Point out where two concepts interact. It is the clearest signal of conceptual thinking.
Because these are also TOK concepts, links to how knowledge is produced and justified are welcome, not off-topic.
⚠️ Common mix-up
Treating concepts as content to memorise. They are tools for thinking about content.
Defining a concept and never using it. The definition earns almost nothing on its own.
Assuming each idea belongs to one concept. Reductionism sits under bias and perspective at once.
Cramming all six into every answer. Depth is what is being marked.
Confusing responsibility with ethics only. It also covers how research is used in society.
Thinking measurement means numbers. It covers qualitative data and how constructs are defined too.
That completes Topic 6. Up next: What Paper 1 Asks For — worth rereading now, because the structure of each section makes much more sense once you know what the concepts are for.
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