Why is "Thinking 'positive' means good and 'negative' means bad" a common mistake in Schizophrenia?

Why it happens: Everyday meaning of the words. How to avoid it: Positive = symptoms ADDED to experience (hallucinations); negative = normal functions LOST (avolition). Source: 9990 Paper 3 mark schemes

Why is "Saying antipsychotics 'cure' schizophrenia" a common mistake in Schizophrenia?

Why it happens: Drugs clearly help. How to avoid it: Drugs MANAGE/reduce symptoms; relapse is common if stopped. Use 'reduce/manage symptoms'.

Why is "Stating 'dopamine causes schizophrenia' without nuance" a common mistake in Schizophrenia?

Why it happens: Over-simplifying the hypothesis. How to avoid it: Say OVERACTIVE dopamine is linked to (positive) symptoms; Carlsson et al. showed glutamate/other systems also interact.

Why is "Evaluating without the named issue/debate" a common mistake in Schizophrenia?

Why it happens: Students give generic evaluation. How to avoid it: Paper 3 'evaluate' usually names a debate (e.g. reductionism) — tie points explicitly to it to reach the top band.

Why is "Calling the token economy classical conditioning" a common mistake in Schizophrenia?

Why it happens: It involves learning. How to avoid it: Token economy = OPERANT conditioning (tokens are secondary reinforcers given AFTER the behaviour).

Clinical Psychology (A Level)Cambridge International A Level Psychology 9990

Schizophrenia

Work through the notes, try the practice questions, then take the quiz. The report tells you exactly what to revise next.

PreviousNext

Learn this Topic

Start with the slides for the quick version, then go deeper with the full study notes.

Short Study Notes in the form of Slides

Read the notes first. If the method in a worked example clicks, you're ready for the questions.

Short Study Notes — Schizophrenia

Start with these resources to cover the key concepts, then work through the practice questions.

Page 1 / 0

Detailed Notes

Full prose, callouts and a recap — built for A* mastery, not just a quick scan.

Take these study notes with you

Download a branded PDF — full prose, callouts, recap and memorise list for Schizophrenia, ready to print or save offline.

Schizophrenia (Clinical Psychology) — Cambridge A Level Psychology 9990 Study Notes (2024-2026)

The first disorder in the Clinical Psychology option. This note builds the background (how disorders are diagnosed; positive vs negative symptoms), then drills the diagnostic criteria, the biological and cognitive explanations (including the dopamine hypothesis and Carlsson et al.), and the biochemical, ECT, CBT and token-economy treatments — with the evaluation that scores on Paper 3.

At a glance

What it is: a severe psychotic disorder disrupting thinking, perception, emotion and behaviour (loss of contact with reality).
Positive symptoms (added to normal experience): hallucinations, delusions, disorganised thought/speech.
Negative symptoms (loss of normal function): avolition (no motivation), anhedonia, alogia (poverty of speech), affective flattening.
Diagnosis: classification systems DSM-5 and ICD-11; symptoms present for a sustained period with impaired functioning.
Biological explanations: genetic (twin/family concordance) and the dopamine hypothesis (excess dopamine activity).
Key study: Carlsson et al. (2000) — neurochemistry beyond dopamine alone (glutamate and other systems interact).
Cognitive explanation: faulty information processing / failure to filter and interpret stimuli.
Treatments: antipsychotic drugs (typical/atypical), ECT, CBT, and the token economy (operant conditioning).

What you’ll learn

Mapped to the Cambridge International A Level 9990 syllabus (2024-2026).

Describe how schizophrenia is diagnosed, including positive and negative symptoms (DSM-5 / ICD-11).
Describe and evaluate biological explanations of schizophrenia (genetic; the dopamine hypothesis; Carlsson et al. 2000).
Describe and evaluate the cognitive explanation of schizophrenia.
Describe and evaluate biological treatments (antipsychotic drugs, ECT).
Describe and evaluate psychological treatments and management (CBT, token economy) and relate to issues & debates.

Diagnosing mental disorders — classification, reliability and validity (background substance)

Disorders are diagnosed against DSM-5/ICD-11 criteria; a good diagnosis must be reliable (consistent) and valid (accurate).

Clinical psychology rests on classifying and diagnosing disorders, so understand this before the symptoms.

Classification systems. Clinicians compare a person's symptoms against agreed criteria in:

the DSM-5 (Diagnostic and Statistical Manual, American Psychiatric Association), and
the ICD-11 (International Classification of Diseases, World Health Organization). A diagnosis is made when enough criteria are met for a sustained time with significant distress or impaired functioning.

Two qualities a diagnosis must have:

Reliability — different clinicians reach the same diagnosis for the same patient (inter-rater reliability), and the diagnosis is stable over time.
Validity — the diagnosis is accurate (it identifies a real, distinct disorder and predicts the right treatment/outcome).

Why this is hard. Mental disorders cannot be seen on a scan like a broken bone; clinicians rely on reported and observed symptoms, which overlap between disorders (comorbidity) and are shaped by culture. This is why diagnosis is a recurring evaluation theme — and why the classic critique of psychiatric diagnosis (e.g. labelling, the loss of reliability/validity) is so often cited.

Why it matters for schizophrenia. Schizophrenia's symptoms are diverse (positive and negative), so reliable, valid diagnosis is genuinely difficult — a strong evaluation point you can apply throughout this disorder.

Diagnosis = matching symptoms to DSM-5 / ICD-11 criteria (with distress/impairment).
Reliability = consistent diagnosis (inter-rater; over time).
Validity = accurate diagnosis (real, distinct disorder; right treatment).
Threats: symptom overlap (comorbidity), cultural differences, reliance on self-report.
Diagnosis reliability/validity = a recurring evaluation theme.

Diagnostic criteria — positive and negative symptoms

Positive symptoms are added experiences (hallucinations, delusions); negative symptoms are losses (avolition, anhedonia, alogia).

Schizophrenia symptoms split into two groups — learn examples of each.

Positive symptoms (an addition to normal experience):

Hallucinations — sensory experiences without a real stimulus (most often auditory — hearing voices).
Delusions — firmly held false beliefs (e.g. of persecution, or grandeur/control).
Disorganised thinking and speech — e.g. derailment, incoherence ('word salad').

Negative symptoms (a loss of normal function):

Avolition — loss of motivation/goal-directed behaviour.
Anhedonia — loss of pleasure.
Alogia — poverty of speech.
Affective flattening — reduced emotional expression.

For diagnosis (DSM-5), two or more symptoms must be present for a significant portion of time (with at least one being a positive symptom), with impaired functioning lasting a sustained period (often around six months including some active symptoms).

Positive = ADDED: hallucinations (often auditory), delusions, disorganised thought/speech.
Negative = LOST: avolition, anhedonia, alogia, affective flattening.
DSM-5: ≥2 symptoms (≥1 positive), sustained, with impaired functioning.
Auditory hallucinations + persecutory delusions are the textbook examples.

Biological explanations — genetics and the dopamine hypothesis

Genetic vulnerability (twin/family concordance) plus the dopamine hypothesis; Carlsson et al. extended this to other neurotransmitters.

Genetic explanation. Schizophrenia runs in families: the closer the genetic relationship, the higher the concordance rate. Identical (MZ) twins show much higher concordance than non-identical (DZ) twins, suggesting a genetic vulnerability — but because concordance is not 100%, genes alone are not the whole story (environment matters too).

The dopamine hypothesis. The classic biochemical explanation: schizophrenia is linked to overactivity of dopamine (too much dopamine activity, or too many/too sensitive D2 receptors) in certain brain pathways.

Supporting evidence: drugs that block dopamine (antipsychotics) reduce positive symptoms; drugs that increase dopamine (e.g. amphetamines) can produce schizophrenia-like symptoms.

Carlsson et al. (2000). A review/analysis arguing the picture is more complex than dopamine alone: other neurotransmitters — especially glutamate — and their interactions with dopamine are involved. This refined the dopamine hypothesis into a broader neurochemical model and helped explain why dopamine-only drugs don't help everyone.

Evaluation in brief. Strong scientific support and effective drug treatments, but reductionist (reduces a complex disorder to brain chemistry) and the direction of cause is unclear (does dopamine cause schizophrenia, or vice versa?).

Genetic: higher concordance with closer relatives; MZ > DZ twins — but not 100% (so not genes alone).
Dopamine hypothesis: overactive dopamine / D2 receptors → positive symptoms.
Evidence: dopamine-blocking drugs help; dopamine-raising drugs mimic symptoms.
Carlsson et al. (2000): involves glutamate + other systems interacting (beyond dopamine alone).
Evaluation: + scientific, effective drugs; − reductionist, cause-effect unclear.

Cognitive explanation

Schizophrenia as faulty information processing — failure to filter, attend to and interpret stimuli correctly.

The cognitive explanation focuses on abnormal information processing.

People with schizophrenia may fail to filter incoming stimuli, becoming overwhelmed by information most people ignore.
Faulty processing of internal experiences can lead to symptoms — e.g. misattributing one's own inner speech to an external voice (a hallucination), or biased reasoning maintaining a delusion.
Cognitive accounts often combine with biology: a biological vulnerability affects the brain, and cognitive misinterpretation of the resulting experiences produces the symptoms.

Link to treatment. This explanation underpins CBT for schizophrenia, which helps patients reinterpret hallucinations/delusions and test beliefs against reality.

Evaluation in brief. Explains the content of symptoms (why a person hears voices and fears them) and leads to a useful therapy, but may describe the mechanism of symptoms rather than their ultimate cause (which may be biological).

Cognitive = faulty information processing (failure to filter/interpret stimuli).
Hallucination = misattributing inner speech to an external source.
Often combines with biology (vulnerability + misinterpretation).
Underpins CBT for schizophrenia.
Evaluation: + explains symptom content + leads to therapy; − may describe not cause.

Treatments — biological (drugs, ECT) and psychological (CBT, token economy)

Antipsychotic drugs and ECT target biology; CBT and the token economy manage symptoms and behaviour.

Biological treatments

Antipsychotic drugs. Typical antipsychotics (e.g. chlorpromazine) block dopamine (D2) receptors, reducing positive symptoms. Atypical antipsychotics (e.g. clozapine) act on dopamine and serotonin, can help negative symptoms too, with fewer movement side effects.
- + Effective and fast for positive symptoms; allow many to live in the community.
- − Side effects (e.g. tardive dyskinesia with typicals); treat symptoms not cause; relapse if stopped.
ECT (electroconvulsive therapy). A controlled electric current induces a brief seizure; used rarely, for severe/treatment-resistant cases.
- + Can work when drugs fail. − Ethical concerns, memory side effects, mechanism unclear.

Psychological treatments / management

CBT for schizophrenia. Helps patients challenge and reinterpret hallucinations and delusions and develop coping strategies (it manages symptoms alongside drugs rather than curing).
- + Addresses the meaning of symptoms; no physical side effects. − Requires insight/engagement; works best with medication.
Token economy (operant conditioning). In hospital settings, desirable behaviours (self-care, social behaviour) earn tokens (secondary reinforcers) exchangeable for privileges.
- + Can improve day-to-day functioning/management. − Doesn't cure; behaviour may not generalise outside the institution; ethical concerns (control).

Key framing: drugs/ECT target biology; CBT/token economy manage symptoms and behaviour — best results often combine approaches.

Typical antipsychotics block dopamine → reduce positive symptoms; atypicals also help negative symptoms, fewer side effects.
ECT: rare, for severe/treatment-resistant cases (ethical + memory concerns).
CBT: reinterpret hallucinations/delusions, coping strategies (manages, with drugs).
Token economy (operant): tokens reinforce desirable behaviour; may not generalise.
Best practice often COMBINES biological + psychological.

Evaluation and issues & debates

Strong scientific base and effective treatments, but reductionism, diagnostic reliability/validity and ethics recur.

Bring these threads together for Paper 3 'evaluate / discuss' questions.

Strengths across the topic

Scientific evidence (twin studies, drug effects, Carlsson et al.) supports biological explanations.
Effective, practical treatments (antipsychotics) that transformed care.

Weaknesses / issues

Reductionism — biological accounts reduce a complex disorder to brain chemistry, possibly ignoring psychological and social factors.
Diagnosis — reliability and validity are imperfect (symptom overlap, cultural bias).
Cause vs effect — abnormal dopamine could be a result of schizophrenia rather than its cause.
Ethics — side effects, ECT, and control issues (token economy).

Relevant issues & debates

Nature vs nurture — genetic vulnerability (nature) interacting with environment/stress (nurture): the diathesis–stress model.
Reductionism vs holism — biology alone vs a fuller bio-psycho-social view.
Idiographic vs nomothetic — general criteria vs the individual's unique experience.
Application to everyday life — diagnosis and treatment in real clinical practice.

Strengths: scientific evidence; effective drug treatments.
Weaknesses: reductionism; imperfect diagnosis (reliability/validity); cause-effect unclear; ethics.
Diathesis–stress = nature (vulnerability) × nurture (stress).
Debates: reductionism vs holism; idiographic vs nomothetic; application.

How it’s examined

Examined in the Clinical Psychology option on Paper 3 (Specialist Options: Theory) — describe (e.g. symptoms, the dopamine hypothesis, a treatment) and evaluate/discuss, usually including a named issue or debate (reductionism, nature–nurture, ethics, diagnosis). On Paper 4 (Application) you may apply treatments or design a study in a clinical scenario. Examiner guidance: distinguish positive vs negative symptoms precisely, use Carlsson et al. to show the dopamine hypothesis was refined, and tie evaluation to the named debate.

Sources: Cambridge International AS & A Level Psychology 9990 syllabus (2024-2026); Carlsson, A. et al. (2000) Network interactions in schizophrenia. Brain Research Reviews, 31: 342-349; DSM-5 (APA) and ICD-11 (WHO) diagnostic criteria; 9990 Learner Guide, Scheme of Work & past Paper 3/4 mark schemes. Last reviewed 2026-05-21.

Master this Topic

Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.

Take this whole topic with you

Download a branded revision sheet — worked examples, formulae, definitions and common mistakes for Schizophrenia, ready to print or save as PDF.

Step-by-step worked examples — Schizophrenia

Step-by-step solutions to past-paper-style questions on schizophrenia, written exactly the way a tutor would explain them at the board.

1State positive vs negative symptoms (2 marks)
Getting started• symptoms, AO1
Question
State one positive and one negative symptom of schizophrenia. (2 marks)
Step-by-step solution
1. Step 1
  Positive (added): hallucinations (e.g. hearing voices) or delusions.
2. Step 2
  Negative (lost): avolition (loss of motivation), anhedonia or alogia.
Answer
Positive: hallucinations/delusions. Negative: avolition/anhedonia/alogia. (2)
Examiner tip
Positive = ADDED to experience; negative = normal function LOST. One of each scores both marks.
2Outline the dopamine hypothesis (2 marks)
Getting started• explanation, AO1
Question
Outline the dopamine hypothesis of schizophrenia. (2 marks)
Step-by-step solution
1. Step 1
  Schizophrenia is linked to overactivity of dopamine.
2. Step 2
  Excess dopamine activity (or too many/too sensitive D2 receptors) is associated with positive symptoms.
Answer
Overactive dopamine activity (excess/sensitive D2 receptors) is linked to (positive) symptoms. (2)
Examiner tip
Naming D2 receptors or 'positive symptoms' adds precision worth the second mark.
3Explain Carlsson et al.'s contribution (4 marks)
Building confidence• explanation, AO2
Question
Explain how Carlsson et al. (2000) extended the dopamine hypothesis. (4 marks)
Step-by-step solution
1. Step 1
  The original hypothesis blamed dopamine alone.
2. Step 2
  Carlsson et al. argued other neurotransmitters are involved, especially glutamate.
3. Step 3
  These systems interact with dopamine rather than dopamine acting in isolation.
4. Step 4
  This refined model helps explain why dopamine-only drugs do not help all patients.
Answer
Carlsson et al. showed schizophrenia involves more than dopamine — glutamate and other systems interact — explaining why dopamine-only drugs don't help everyone. (4)
Examiner tip
AO2 credit comes from the 'theory was refined' logic (glutamate interaction → drug limits), not just naming the study.
4Typical vs atypical antipsychotics (4 marks)
Building confidence• treatment, AO2
Question
Explain one difference between typical and atypical antipsychotic drugs. (4 marks)
Step-by-step solution
1. Step 1
  Typical antipsychotics mainly block dopamine (D2) receptors.
2. Step 2
  They reduce positive symptoms but can cause movement side effects (e.g. tardive dyskinesia).
3. Step 3
  Atypical antipsychotics act on dopamine AND serotonin.
4. Step 4
  They can also help negative symptoms and tend to have fewer movement side effects.
Answer
Typicals block dopamine (positive symptoms, more movement side effects); atypicals act on dopamine + serotonin (also help negative symptoms, fewer side effects). (4)
Examiner tip
The markable contrast is the neurotransmitter action AND the symptom/side-effect difference.
5Describe the token economy (6 marks)
Stretch• treatment, AO1, Paper 3
Question
Describe how a token economy can be used to manage schizophrenia. (6 marks)
Step-by-step solution
1. Step 1
  A token economy is based on operant conditioning (positive reinforcement).
2. Step 2
  Desirable behaviours (self-care, social interaction) are identified as targets.
3. Step 3
  When the patient performs a target behaviour they immediately receive a token.
4. Step 4
  Tokens are secondary reinforcers — they have no value themselves but can be exchanged.
5. Step 5
  Tokens are exchanged for privileges or rewards the patient values.
6. Step 6
  Over time, target behaviours increase, improving day-to-day functioning (management, not cure).
Answer
Operant token economy: target behaviours earn tokens (secondary reinforcers) exchangeable for privileges, increasing desirable behaviour and improving functioning. (6)
Examiner tip
Top band needs the operant basis, tokens as secondary reinforcers, exchange, and that it manages (not cures).
6Evaluate — reductionism (4 marks)
Stretch• evaluation, AO3, reductionism, exam-technique
Question
Evaluate the biological explanation of schizophrenia with reference to reductionism. (4 marks)
Step-by-step solution
1. Step 1
  Point. The biological explanation is reductionist.
2. Step 2
  Explain. It reduces a complex disorder to brain chemistry (dopamine/genes).
3. Step 3
  Evidence (in context). It can ignore psychological and social factors such as stress, family environment or cognition.
4. Step 4
  Link. A diathesis–stress (holistic) view may explain schizophrenia better than biology alone.
Answer
The biological account is reductionist — reducing schizophrenia to dopamine/genes and ignoring psychological/social factors; a holistic diathesis–stress view may be better. (4)
Examiner tip
When a debate is named, you must explicitly tie the point to it (reductionism → ignores other factors → holism).

Model Answers — Schizophrenia

High-scoring sample answers for schizophrenia on the Cambridge International A Level 9990 paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.

Question 1
9990 Paper 3 (describe) style6 marks
Q (6 marks). Describe the biological explanation of schizophrenia.
Model answer
The biological explanation argues schizophrenia has genetic and biochemical causes. The genetic account points to family and twin studies: the closer the genetic relationship to a person with schizophrenia, the higher the concordance rate, and identical (MZ) twins show higher concordance than non-identical (DZ) twins, suggesting an inherited vulnerability — though concordance is not 100%, so genes are not the only cause.

The biochemical account is the dopamine hypothesis: schizophrenia is associated with overactivity of dopamine (excess dopamine or oversensitive D2 receptors), which is linked to positive symptoms. Supporting this, dopamine-blocking drugs reduce symptoms while dopamine-raising drugs (e.g. amphetamines) can produce schizophrenia-like symptoms. Carlsson et al. (2000) refined this, showing other neurotransmitters such as glutamate interact with dopamine, so the disorder involves more than dopamine alone.
Why this scores
Why this scores well. It covers both genetic and biochemical strands accurately, uses concordance evidence, names D2 receptors and positive symptoms, and brings in Carlsson et al. to refine the hypothesis — strong AO1.
Question 2
9990 Paper 3 (evaluate with named debate) style10 marks
Q (10 marks). Evaluate the biological explanation and treatment of schizophrenia, including a discussion of reductionism.
Model answer
Strength 1 — scientific evidence. The biological explanation is supported by objective evidence: twin studies show higher MZ than DZ concordance, and drug studies show dopamine-blocking antipsychotics reduce symptoms while dopamine agonists mimic them. This makes the account testable and credible.

Strength 2 — effective, practical treatment. It has produced antipsychotic drugs that effectively reduce positive symptoms and allow many patients to live in the community, a major real-world benefit, and Carlsson et al.'s refinement has guided newer drug targets.

Weakness 1 — reductionism (named debate). The explanation is reductionist: it reduces a complex disorder to dopamine and genes, potentially ignoring psychological and social factors such as stress, family environment and cognition. A holistic account, such as diathesis–stress (a genetic vulnerability triggered by environmental stress), may explain schizophrenia more fully.

Weakness 2 — cause and effect. Much evidence is correlational: abnormal dopamine activity could be a result of schizophrenia rather than its cause, and the fact that drugs work does not prove a chemical cause (the treatment-aetiology fallacy).

Conclusion. The biological explanation is scientifically strong and has produced effective treatments, but its reductionism and the unresolved cause-and-effect problem mean it is best combined with psychological and social factors in a diathesis–stress model rather than used alone.
Why this scores
Why this reaches the top band. Two strengths and two weaknesses, the named debate (reductionism) explicitly developed toward holism/diathesis–stress, and a reasoned conclusion (AO3).
Question 3
9990 Paper 3 (describe) style6 marks
Q (6 marks). Describe how schizophrenia is diagnosed, including positive and negative symptoms.
Model answer
Schizophrenia is diagnosed by matching a person's symptoms to the criteria in classification systems such as the DSM-5 or ICD-11. A diagnosis requires symptoms to be present for a sustained period with impaired functioning.

Symptoms are grouped as positive and negative. Positive symptoms are experiences added to normal functioning: hallucinations (sensory experiences without a real stimulus, often hearing voices), delusions (firmly held false beliefs, e.g. of persecution) and disorganised thinking/speech. Negative symptoms are losses of normal functioning: avolition (loss of motivation), anhedonia (loss of pleasure), alogia (poverty of speech) and affective flattening (reduced emotional expression). For a DSM-5 diagnosis, two or more symptoms (at least one positive) must be present for a significant time with impaired functioning.
Why this scores
Why this scores well. It names the classification systems, distinguishes positive (added) from negative (lost) symptoms with accurate examples, and states the diagnostic threshold — clean AO1.
Question 4
9990 Paper 4 (application) style8 marks
Q (8 marks). A psychologist wants to investigate whether a token economy improves self-care in patients with schizophrenia. Suggest how this could be studied, with reference to research methods.
Model answer
A suitable method would be a field experiment / controlled observation in a hospital ward. The independent variable is whether patients receive a token economy programme; the dependent variable is self-care behaviour, operationalised as the number of target behaviours (e.g. washing, dressing, tidying) observed per day using clear behavioural categories.

Patients could be allocated to a token economy condition or a control condition, with self-care rated by two independent observers to check inter-observer reliability. Baseline self-care would be measured first, then again after several weeks, so any increase can be compared. Standardising the tokens, target behaviours and exchange rules would control extraneous variables. Ethical safeguards are essential: informed consent (from patients or carers), the right to withdraw, protection from harm, and ensuring the programme is not coercive. Strengths are high ecological validity (a real ward) and objective behavioural data; a weakness is limited control of extraneous variables in a real setting, and findings may not generalise beyond the institution.
Why this scores
Why this scores well. It operationalises the IV/DV, builds in reliability (two observers/categories), controls and ethics, and evaluates the design — exactly the Paper 4 application skills.

Key Definitions and Keywords — Schizophrenia

Definitions to memorise and the exact keywords mark schemes credit for schizophrenia answers — sharpened from recent examiner reports for the 2026 Cambridge International A Level 9990 sitting.

Schizophrenia
Examiner keyword
A severe psychotic disorder disrupting thinking, perception, emotion and behaviour, with positive and negative symptoms.
Positive symptoms
Examiner keyword
Symptoms ADDED to normal experience — hallucinations, delusions and disorganised thinking/speech.
Negative symptoms
Examiner keyword
Losses of normal functioning — avolition, anhedonia, alogia and affective flattening.
Hallucination
Examiner keyword
A sensory experience without a real external stimulus (often auditory — hearing voices).
Delusion
Examiner keyword
A firmly held false belief resistant to evidence (e.g. persecution, grandeur).
Dopamine hypothesis
Examiner keyword
The theory that schizophrenia is linked to overactive dopamine activity (excess/oversensitive D2 receptors).
Antipsychotic drugs
Examiner keyword
Drugs that reduce psychotic symptoms; typical antipsychotics block dopamine, atypicals act on dopamine and serotonin.
Token economy
Examiner keyword
An operant-conditioning programme rewarding desirable behaviour with tokens (secondary reinforcers) exchangeable for privileges.
Concordance rate
The probability that, if one twin/relative has a disorder, the other does too — used in genetic studies.
Reductionism
Examiner keyword
Explaining a complex phenomenon by reducing it to simpler parts (e.g. schizophrenia to dopamine/genes).

Common Mistakes and Misconceptions — Schizophrenia

The traps other students keep falling into on schizophrenia questions — taken from recent Cambridge International A Level 9990 examiner reports and mark schemes — and how to avoid them.

✕Thinking 'positive' means good and 'negative' means bad
9990 Paper 3 mark schemes
Why it happens
Everyday meaning of the words.
How to avoid it
Positive = symptoms ADDED to experience (hallucinations); negative = normal functions LOST (avolition).
✕Saying antipsychotics 'cure' schizophrenia
Why it happens
Drugs clearly help.
How to avoid it
Drugs MANAGE/reduce symptoms; relapse is common if stopped. Use 'reduce/manage symptoms'.
✕Stating 'dopamine causes schizophrenia' without nuance
Why it happens
Over-simplifying the hypothesis.
How to avoid it
Say OVERACTIVE dopamine is linked to (positive) symptoms; Carlsson et al. showed glutamate/other systems also interact.
✕Evaluating without the named issue/debate
Why it happens
Students give generic evaluation.
How to avoid it
Paper 3 'evaluate' usually names a debate (e.g. reductionism) — tie points explicitly to it to reach the top band.
✕Calling the token economy classical conditioning
Why it happens
It involves learning.
How to avoid it
Token economy = OPERANT conditioning (tokens are secondary reinforcers given AFTER the behaviour).

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Schizophrenia

Short Study Notes in the form of Slides

Short Study Notes — Schizophrenia

Detailed Notes

What you’ll learn

How it’s examined

1State positive vs negative symptoms (2 marks)

2Outline the dopamine hypothesis (2 marks)

3Explain Carlsson et al.'s contribution (4 marks)

4Typical vs atypical antipsychotics (4 marks)

5Describe the token economy (6 marks)

6Evaluate — reductionism (4 marks)

Schizophrenia

Positive symptoms

Negative symptoms

Hallucination

Delusion

Dopamine hypothesis

Antipsychotic drugs

Token economy

Concordance rate

Reductionism

✕Thinking 'positive' means good and 'negative' means bad

✕Saying antipsychotics 'cure' schizophrenia

✕Stating 'dopamine causes schizophrenia' without nuance

✕Evaluating without the named issue/debate

✕Calling the token economy classical conditioning

Practice questions

Past paper style quiz

Assess your understanding