Edexcel A Level Psychology 9PS0

Learn 200 Edexcel A Level Psychology words for comparing explanations, applying research and evaluating evidence. Every entry gives a plain-English meaning and a usage example.

For Pearson Edexcel Psychology 9PS0, Papers 1 and 2 each last 135 minutes and carry 90 marks and 35%. Paper 3 lasts 120 minutes and carries 80 marks and 30%. Use the extended timings for Papers 1 and 2 when practising for 2026 onward.

200 words and examples
Exam requirements and worked examples
Fencing Method
Practice exercises

200 essay vocabulary words and examples

Foundations, applications and psychological skills

social identity — part of self-concept that comes from group membership. apply social identity to a comparison between groups.
in-group — a group a person sees themselves as belonging to. explain the conditions for in-group favouritism.
out-group — a group a person sees as outside their own group. test whether a response differs for an out-group.
prejudice — an attitude toward a person or group based on group membership. distinguish prejudice from discriminatory behaviour.
working memory — a system for temporarily holding and manipulating information. relate the task to the demands on working memory.
phonological loop — a component of working memory associated with speech-based information. explain why two verbal tasks may interfere.
central executive — a proposed system directing attention and coordinating working-memory activity. state which task demands control of attention.
neurotransmitter — a chemical messenger released by neurons to influence another cell. link a neurotransmitter claim to the evidence used.
heritability — the proportion of variation in a trait associated with genetic differences within a studied population and environment. avoid treating heritability as the genetic share of one person’s behaviour.
classical conditioning — learning in which one stimulus comes to predict another. identify the conditioned stimulus after learning.
operant conditioning — learning in which consequences affect how often behaviour occurs. distinguish reinforcement from punishment.
negative reinforcement — increasing a behaviour by removing or avoiding an aversive condition. explain why the behaviour becomes more frequent.
modelling — demonstrating a behaviour that another person may observe and learn. state which behaviour the model demonstrates.
vicarious reinforcement — an increase in the likelihood of imitating a behaviour after seeing a model rewarded. compare imitation after reward and after no reward.
diagnostic reliability — consistency of diagnostic judgements across clinicians or occasions. compare whether clinicians using the same criteria reach similar decisions.
diagnostic validity — how well a diagnosis captures the condition it is intended to identify. test diagnostic validity against relevant evidence.
comorbidity — the presence of more than one condition in the same person. explain how comorbidity could complicate interpretation of treatment outcomes.
standardisation — keeping procedures and instructions consistent. standardisation reduces unwanted variation between sessions.
generalisability — how far findings may apply beyond the people or conditions studied. qualify generalisability when the study uses a narrow sample.
operationalisation — specifying how a concept or variable will be measured or manipulated. operationalise performance as the number of correct responses.

Concepts and contexts in IB Psychology

perspective — a standpoint or framework used to interpret behaviour. compare cognitive and sociocultural perspectives.
responsibility — an obligation to consider the consequences of inquiry or action. researcher responsibility includes protecting participants.
measurement — the process of assigning observations or scores using a rule. evaluate the measurement of recall.
change — a difference over time or between states. distinguish measured change from a practice effect.
causation — a relationship in which one factor produces an effect. a controlled experiment can support a claim about causation.
bias — a systematic influence on observations or conclusions. question whether observer bias affected the record.
cognitive — relating to mental processes such as memory or reasoning. a cognitive account of memory.
biological — relating to bodily systems or processes. a biological explanation of behaviour.
sociocultural — relating to social relationships and cultural contexts. a sociocultural explanation of learning.
context — the situation in which a concept or behaviour is examined. apply the concept in the learning and cognition context.
triangulation — using several methods, sources or perspectives to examine a question. triangulation can test whether findings converge.
reflexivity — attention to how a researcher’s position affects inquiry. reflexivity is important when interpreting interviews.
reactivity — behavioural change caused by awareness of being studied. reactivity can affect a classroom observation.
transferability — the potential relevance of a finding to another context. assess the transferability of the finding.
positionality — the way a person’s role or background shapes their standpoint. researcher positionality can influence interpretation.
developmental — relating to changes across the lifespan. consider developmental differences in task performance.
dyadic — involving two people or units in a relationship. a dyadic interaction between partners.
reciprocity — mutual influence or exchange. reciprocity can shape relationships.
enculturation — learning the practices and meanings of a culture. enculturation can shape expectations.
cross-cultural — involving comparison or work across cultures. a cross-cultural design requires comparable measures.

Memory, learning and explanation

encoding — conversion of information into a form that can be stored. encoding may depend on attention.
retrieval — accessing stored information. a cue can aid retrieval.
reconstruction — rebuilding a memory using stored information and other inputs. reconstruction may incorporate later wording.
interference — disruption of recall or learning by competing information. similar material can produce interference.
misinformation — inaccurate information that can influence a later report. post-event misinformation may change a response.
leading — phrased in a way that suggests a particular answer. a leading question can affect an estimate.
schema — an organised framework of prior knowledge. a schema can shape interpretation.
cue — a signal that helps evoke a response or memory. a contextual cue can prompt recall.
conformity — changing behaviour or judgement in response to group pressure. public conformity may reflect social pressure.
compliance — outward agreement or action without necessarily changing private belief. compliance can end when pressure is removed.
internalisation — acceptance of a view as part of one’s own belief. internalisation can persist privately.
obedience — following a direct instruction from an authority. obedience depends partly on perceived authority.
attachment — an enduring emotional bond. evaluate how attachment is assessed.
reinforcement — a consequence that increases the likelihood of a behaviour. reinforcement can maintain a learned response.
conditioning — learning through associations or consequences. compare different forms of conditioning.
mediational — concerned with processes that intervene between stimulus and response. a mediational process such as attention.
reductionism — explaining a complex phenomenon through simpler components or a single level. evaluate whether the account is reductionist.
determinism — the view that behaviour is governed by causes or conditions. compare different forms of determinism.
idiographic — focused on individuals and their particular experiences. an idiographic approach can reveal personal meaning.
nomothetic — aimed at general patterns or laws. a nomothetic approach seeks common patterns.

Design, measurement and ethics

attribute — identify where an idea or quotation comes from. attribute the statistic to Source A.
construct — an abstract concept that cannot be observed directly. memory accuracy is a construct.
validity — how well a measure or inference supports its intended interpretation. evaluate whether the task measures the construct.
reliability — consistency of measurement or results under specified conditions. check inter-rater reliability.
replication — repeating a study or procedure to test a finding. a replication uses the same core manipulation.
sampling — selecting cases or participants from a population. sampling affects who is represented.
random allocation — assigning participants to conditions by chance. random allocation can reduce systematic group differences.
control condition — a comparison condition without the critical manipulation or with an alternative treatment. compare the experimental and control conditions.
confound — a variable that changes with the factor of interest and offers another explanation. prior exposure could confound the result.
cite — identify the source of material used in an argument. cite the survey in Source B.
demand characteristics — cues that suggest what a study expects from participants. demand characteristics may influence answers.
social desirability — a tendency to give answers viewed favourably by others. social desirability can affect self-reports.
observer effect — a change associated with being observed. the observer effect may alter classroom behaviour.
generalisation — extension of a finding beyond the cases or conditions studied. limit generalisation from a narrow sample.
consent — agreement to participate based on appropriate information and choice. obtain informed consent.
debriefing — explaining the study after participation and addressing questions or concerns. debriefing can explain why details were withheld.
anonymity — a condition in which identities are not known or linked to responses. anonymous responses can reduce some disclosure concerns.
confidentiality — protection against unauthorised disclosure of information. maintain confidentiality in the interview records.
self-report — information participants provide about themselves. a self-report may differ from observed behaviour.
attrition — loss of participants over the course of a study. attrition can change the composition of the final sample.

Taking a position

claim — a statement you want the reader to accept. make a claim.
stance — your position on a question. take a clear stance.
thesis — the central position or interpretation your response develops. support the thesis.
premise — an idea the argument starts from. question the premise.
assumption — something treated as true without being established. test the assumption.
assert — state a position firmly. assert that access matters.
argue — give reasons in support of a position. argue for a trial.
maintain — continue to hold or defend a view. maintain that the policy is fair.
contend — put forward a position that can be challenged. contend that the proposal is workable.
justify — give sufficient reasons for a decision or judgement. justify the expense.
advocate — publicly support an action or change. advocate for reform.
defend — answer criticism of a view or choice. defend a decision.
qualify — limit a statement so it applies only where warranted. qualify the conclusion.
concede — acknowledge a valid point made by the other side. concede that costs may rise.
rebut — answer an opposing claim with reasoning or evidence. rebut the objection.
counterargument — a reasoned objection to a position. address a counterargument.
reservation — a concern that makes agreement incomplete. express a reservation.
distinguish — show what makes two things different. distinguish cost from value.
criteria — standards used to judge something. agree on the criteria.
verdict — a final judgement reached after consideration. reach a verdict.

Using evidence and reasoning

evidence — information that helps establish a claim. draw on evidence.
example — a specific case that makes a general point clearer. give a concrete example.
illustrate — make an idea clearer through a case or detail. illustrate the difficulty.
demonstrate — show how or why something is true. demonstrate a connection.
substantiate — support a claim with convincing information. substantiate the allegation.
corroborate — provide independent support for an existing account. corroborate the witness’s account.
infer — draw a conclusion from available clues. infer a motive from the wording.
imply — suggest a meaning without saying it directly. imply that change is possible.
interpret — explain what something means in context. interpret a figure in context.
analyse — examine how parts work together. analyse the writer’s choices.
evaluate — judge the strength, quality or value of something. evaluate the proposal.
plausible — reasonable enough to believe given what is known. a plausible explanation.
credible — worthy of belief or trust. a credible source.
relevant — directly connected to the issue being considered. relevant to the question.
sufficient — enough for the purpose or conclusion at hand. sufficient for a limited trial.
representative — typical enough to reflect a larger group. a representative sample.
anecdote — a brief account of a particular incident. open with an anecdote.
limitation — something that restricts what a method or claim can establish. acknowledge a limitation.
contradict — state or show something incompatible with another claim. contradict the earlier finding.
synthesise — combine ideas from separate sources into a new account. synthesise competing accounts.

Connecting ideas

whereas — introduces a clause that contrasts with another. whereas the first option costs less.
although — introduces a fact that qualifies the main statement. although demand may rise.
however — signals a contrast or change in direction. however, costs remain uncertain.
nevertheless — signals that a point still holds despite a difficulty. nevertheless, the trial could go ahead.
conversely — introduces a contrasting relationship in the reverse direction. conversely, lower demand can free capacity.
similarly — points out a meaningful likeness. similarly, smaller groups need space.
likewise — shows that a similar point applies elsewhere. likewise, evening users need lighting.
consequently — introduces a result of what came before. consequently, the queue grew.
therefore — introduces a conclusion or result that follows. therefore, a trial is justified.
furthermore — adds a supporting point. furthermore, the existing room is free.
specifically — narrows the discussion to a precise detail. specifically, the plan would add two sessions.
instead — signals a replacement or different choice. instead, use the current building.
alternatively — introduces another option. alternatively, change the timetable.
otherwise — indicates what happens under different conditions. book early, otherwise places may fill.
provided — introduces a condition when used with a following clause. provided that staffing is adequate.
despite — introduces something that fails to prevent the main outcome. despite the delay.
unlike — marks a difference between two things. unlike the previous scheme.
respectively — matches items with values in the same stated order. costs were $5 and $8, respectively.
overall — signals a judgement about the whole picture. overall, the benefits are modest.
ultimately — identifies what matters after other factors are considered. ultimately, the decision depends on demand.

Explaining cause and effect

cause — produce or bring about an outcome. cause avoidable delays.
contribute — play a part in bringing about an outcome. contribute to overcrowding.
trigger — set a process or reaction in motion. trigger a review.
accelerate — make a process happen faster. accelerate the transition.
intensify — make something stronger or more severe. intensify competition.
exacerbate — make an existing problem worse. exacerbate existing inequalities.
mitigate — reduce the severity or harmful effect of something. mitigate the harm.
prevent — stop something from happening. prevent further damage.
deter — discourage someone from taking an action. deter people from taking risks.
enable — make an action possible. enable students to attend.
facilitate — make an action or process easier. facilitate access to training.
reinforce — strengthen an effect, belief or behaviour. reinforce an existing pattern.
undermine — weaken something, often gradually. undermine public trust.
sustain — keep something going over time. sustain the improvement.
displace — push something or someone out of an existing place or role. displace smaller operators.
redistribute — change how something is shared. redistribute public funds.
consequence — an outcome that follows an action or event. an unintended consequence.
mechanism — the process through which an effect occurs. identify the mechanism.
correlation — a pattern in which two things vary together. observe a correlation.
constraint — a condition that limits what can be done. work within a budget constraint.

Testing evidence and reasoning

intermediate — coming between earlier reasons and the main result. identify an intermediate conclusion.
unstated — implied without being expressed directly. an unstated assumption about access.
premiss — a proposition offered as a reason for a conclusion. test whether the premiss is true.
jointly — together rather than separately. the two reasons jointly support the claim.
deductive — involving an inference intended to follow necessarily. a deductive argument with a missing premiss.
inductive — involving reasoning that extends beyond the observed cases. an inductive inference from a survey.
abductive — concerned with inferring a likely explanation. an abductive inference from an unexpected result.
counterinstance — an example that goes against a general claim. one counterinstance challenges the rule.
equivocal — open to different meanings or interpretations. an equivocal use of the word free.
circular — using the conclusion itself as part of its supposed support. circular reasoning provides no independent reason.
fallacy — a flaw in reasoning. identify a fallacy in a forced choice.
confounder — a factor that can distort a proposed causal relationship. distance may be a confounder.
denominator — the reference total against which a count or rate is expressed. check the denominator in the reported rate.
response — a reply or a contribution to a survey. a low survey response rate.
self-selection — the process by which participants choose whether to take part. self-selection limits the survey.
comparability — the extent to which items can be fairly compared. question comparability across the two periods.
interested — having a stake that could affect an account. an interested source may still provide accurate data.
contemporaneous — made or existing at the same time as an event. contemporaneous records of attendance.
weight — the importance assigned to a piece of evidence. give more weight to direct measurements.
decisive — strong enough to settle a question under the available evidence. the documents do not provide decisive support.

Evaluating limits and assumptions

presuppose — treat something as already true before arguing. presuppose that demand is fixed.
conflate — treat distinct things as if they were the same. conflate availability with accessibility.
elide — leave out or pass over a distinction or detail. elide the difference between choice and constraint.
overgeneralise — draw a conclusion that covers more cases than the evidence allows. overgeneralise from one institution.
extrapolate — extend an observed pattern beyond the data available. extrapolate from a small pilot.
circumscribe — limit something to a defined range. circumscribe the policy’s application.
predicate — base a claim or decision on a condition. predicate success on continued funding.
reductive — simplifying a subject in a way that loses important detail. a reductive account of motivation.
tenable — capable of being maintained under criticism. a tenable explanation of the discrepancy.
fallacious — based on faulty reasoning. a fallacious comparison between unlike cases.
ambivalent — having mixed or opposing feelings about something. an ambivalent response to regulation.
normative — concerned with what ought to be done or valued. a normative claim about fairness.
empirical — based on observation or evidence from experience. empirical evidence on take-up.
asymmetry — a significant difference between two sides that are compared. an asymmetry in bargaining power.
contention — a claim presented as part of an argument. the contention that access is universal.
caveat — a warning or limitation attached to a statement. accept the proposal with a caveat.
paradox — an apparently contradictory situation or statement. the paradox of choice without access.
compatibility — ability to work or coexist together. compatibility with local practice.
salience — importance or prominence in a particular context. the salience of cost in the debate.
commensurate — matching another thing in size or degree. support commensurate with need.

Exam requirements and worked examples

Match extended writing to the paper

Paper 1, Foundations in Psychology, covers social, cognitive and biological psychology and learning theories. It also includes issues and debates. Paper 2, Applications of Psychology, combines compulsory clinical psychology with a choice of criminological, child or health psychology. The clinical section includes a 20-mark response.

Paper 3, Psychological Skills, covers research methods, a synoptic review of studies, and issues and debates. The issues and debates section contains two extended responses. Practise explaining how a method affects a conclusion and comparing what evidence from different topic areas can establish. If a question asks for a named study, use it for the precise function specified by the prompt.

Official specifications and sources

Worked evaluation about a working-memory explanation

Imagine a study comparing performance while participants complete two verbal tasks with performance while they complete one verbal and one spatial task. A working-memory explanation predicts more interference for tasks drawing on the same resources. Explain how the different pairings create different demands and what pattern the prediction would lead you to expect.

Now examine whether the paired conditions differ in difficulty. If the two verbal tasks are harder individually, lower performance in that condition may have another explanation. Matching the tasks more closely or measuring performance on each task alone would help. You could then compare the change when tasks are paired rather than relying on the final scores alone.

A reasoned judgement might say the results support the proposed distinction if the study controls relevant differences and the predicted interference pattern appears. Alternative evidence and task choice matter to the conclusion. This invented example is a practice model. In the exam, refer to relevant evidence and course studies.

Fencing Method for a research term

Start with The tasks interfere. Add detail. Accuracy drops when two verbal tasks are performed together. Refine the tone. The pattern is consistent with competition for speech-based resources. Add logic. The inference is stronger if individual task difficulty is similar and the predicted pattern differs across pairings. Transfer the reasoning to another study of divided attention.

Try fencing diagnostic reliability. Name the clinicians or occasions being compared and define what counts as agreement. Then distinguish consistency from validity. Consistent classification is useful for interpreting agreement, while a claim about validity needs evidence that the diagnosis captures the intended condition.

Make an evaluation point testable

Identify the specific feature of a study you want to evaluate. State how it could affect the data and what follows for the claim. If a study uses an artificial task, explain which feature of everyday behaviour is missing and why it matters. The same controlled task could be useful for isolating a process even when wider application is uncertain.

Contrast one strength and one limit using the same aim. A controlled setting may reduce differences between conditions. A field setting may provide a better test of the behaviour in an ordinary context. Decide which advantage matters most for the question and support the comparison using examples.

Use issues and debates to compare evidence

Choose a debate such as whether an explanation gives too much weight to one level of analysis. State how each account explains the same behaviour. Compare which evidence directly tests its mechanism. If a biological measure is associated with a response, ask what the design can establish about direction and causality.

Now bring in a second topic. Explain why a similar method or limitation matters there and where the comparison breaks down. A synoptic point gains value when it reveals a common issue in two examples. Name the consequence for the argument rather than listing the topic names.

Build a conclusion around the strongest evidence

Write one sentence about what the best evidence supports and one about its main limit. Give each a specific study detail. Then decide how much confidence the combination justifies. If the evidence explains a result only under a particular task condition, make that scope explicit in the judgement.

Practise transferring the same plan to the clinical section. Distinguish evidence about whether a measure is consistent, whether it captures the intended construct and whether the finding can be applied to another population. Use the distinction that the question calls for.

Frequently asked questions

Do Papers 1 and 2 still last two hours? Pearson increased each to two hours 15 minutes from summer 2026. Can I use a study twice? Use it when it has a clear role in each argument. Is one evaluation label enough? Explain how the feature changes the strength or scope of the conclusion.

Test a claim about behaviour against two explanations

Choose a behaviour and write a mechanism for each explanation. For example, observed imitation could follow attention to a model and its consequences. A separate explanation might focus on what participants think the researcher expects. Identify evidence that would favour one account over the other. Changing whether the model is rewarded, while holding instructions constant, could help test one part of the comparison.

Then examine what the measure captures. An immediate choice during a study may give evidence about behaviour in that setting. Evidence about persistence or transfer would require observations later or in a different context. Build the distinction into the judgement instead of making a broad claim about every form of learning.

Make Paper 3 comparisons use the same criterion

Select one method from a social study and one from a cognitive study. Give them a shared criterion, such as how convincingly each design supports a causal claim. Compare which variables were manipulated, what was measured and which alternatives were controlled. If one study pursues a different aim, explain how that affects the comparison.

Write a conclusion that identifies the most consequential design difference. If one method is stronger for causal inference and the other better captures everyday behaviour, say which advantage matters for the question and why. Then revise the paragraph to make the evidence traceable to the named studies rather than referring to broad methods alone.

Choose the evidence for a clinical argument carefully

Practise separating evidence about classification from evidence about treatment outcomes. Consistent agreement between clinicians can support a claim about reliability. It gives less direct evidence about whether the categories identify an underlying condition or whether a treatment helps people. Choose an appropriate measure for the claim and specify who was studied.

If a question involves change after a treatment, consider the comparison group and how the outcome was recorded. Improvement during a study may be consistent with a benefit. The design and measure affect how confidently it can be attributed to treatment. Decide what the evidence supports, name the main uncertainty and explain its consequence for the judgement.

Apply that comparison to a named course study and explain how its design affects the inference.

Top 200 Vocabulary Word List for Pearson Edexcel A Level Psychology (9PS0) | Essay Writing