Explain group development and prevent faulty decisions
Apply Tuckman and Jensen’s stages and Belbin’s team roles, then identify groupthink symptoms and Forsyth’s cognitive errors and choose safeguards for a better decision.
Section OPTION-OR-4.3.1 · 4.3.1 Group development and decision-making
Original StudyForA teaching mapped to Cambridge Psychology 9990 Organisational Psychology section 4.3, 2028–2030 Version 1. Examples are not Cambridge materials or mark schemes. Models and studies are bounded by their evidence
Before you begin
- This lesson covers section 4.3.1 of the 2028–2030 syllabus. Group-development and decision-error frameworks are lenses for evidence, not guarantees that a group passes through fixed stages or that one safeguard ensures a correct decision.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
A group relies on an old report after the report has been shown to be inaccurate. Which Forsyth category fits best?
What you will learn
- Tuckman and Jensen’s five stages of group development
- Belbin’s nine team roles
- Groupthink features, examples and prevention strategies
- Forsyth’s sins of commission, omission and imprecision, with their subtypes
Tuckman and Jensen describe five possible stages
Forming: people meet, learn the task and look for direction. Storming: differences, goals or ways of working become visible. Norming: members develop shared expectations and ways to coordinate. Performing: attention can focus on the task with more established collaboration. Adjourning: a temporary group finishes, hands over work or separates.
The stages are a useful description, not a timetable every group must follow. A team may skip, revisit or experience several patterns at once. A new member, changed task or conflict can disrupt established routines. Diagnose the group from evidence about its task and relationships instead of assuming its stage from its age.
Belbin groups nine ways people can contribute
Social roles are Resource Investigator (explores outside ideas and contacts), Teamworker (supports cooperation) and Co-ordinator (clarifies goals and draws on others’ strengths). Thinking roles are Plant (offers original ideas), Monitor Evaluator (analyses options) and Specialist (contributes focused expertise). Action roles are Shaper (drives progress), Implementer (turns plans into practical work) and Completer Finisher (checks detail and completion).
These are clusters of behaviour that can help a team progress, not job titles, diagnoses or fixed personality boxes. A person may contribute in several ways, and a role that is useful at one stage may be less useful at another. A balanced team considers the task and missing contributions rather than ranking people or treating a questionnaire as destiny.
Groupthink is pressure for agreement that weakens appraisal
Janis used groupthink to describe a decision process in a cohesive, insulated group where pressure to preserve agreement can reduce critical evaluation. Possible symptoms include an illusion of invulnerability, collective rationalisation, belief in the group’s inherent morality, negative stereotypes of outsiders, pressure on dissenters, self-censorship, an illusion of unanimity and ‘mindguards’ who filter inconvenient information.
An often-taught example is the US government’s Bay of Pigs decision, analysed retrospectively by Janis. It illustrates questions to ask about discussion and dissent; it does not prove that groupthink was the single cause. A poor outcome alone is not evidence of groupthink, and a cohesive team does not automatically make poor decisions. Look for the decision process and competing explanations.
Safeguards include a leader who withholds an initial preference, explicit invitations to disagree, independent subgroups, an assigned critical reviewer, outside expertise, checking disconfirming evidence and a second review before commitment. These steps reduce pressure but cannot guarantee a correct answer; the group still needs reliable information and clear criteria.
Forsyth groups decision errors by how information is mishandled
Sins of commission misuse information: belief perseverance keeps relying on evidence already shown to be inaccurate; sunk-cost bias preserves a failing plan because time or money has already been spent; extra-evidentiary bias uses information the group was told to exclude; hindsight bias overestimates how well an outcome could have been predicted beforehand.
Sins of omission leave out useful information: base-rate bias neglects relevant general-frequency evidence; the fundamental attribution error overemphasises a person’s disposition and underestimates situational causes; confirmation bias fails to seek evidence that could disconfirm the current conclusion.
Sins of imprecision use shortcuts that oversimplify: availability relies on examples that are easy to recall; conjunction bias treats a detailed combination of events as more likely than one of its parts; representativeness relies too heavily on a seemingly typical match. A label should name the information error and show how it affects this decision.
A real decision can contain more than one error. For example, after one vivid equipment failure a team might overestimate how common it is (availability), ignore base-rate records (omission) and keep an already funded but ineffective fix (sunk cost). Ask what information was used, missed or oversimplified before classifying the error.
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
- Tuckman and Jensen (1977), Stages of Small-Group Development Revisited
- Belbin, the nine Team Roles
- Stanford Medicine, Janis’s groupthink symptoms summary
- Cambridge 9990 Paper 41 mark scheme (June 2023), Forsyth decision errors
- Kerr, MacCoun and Kramer (1996), Bias in Judgment: Comparing Individuals and Groups
Pause and explain
Which action is a direct safeguard against pressure for agreement?
Worked example
A school team chooses a costly platform after one dramatic success story. It ignores its own trial data, keeps the plan because it has already paid for it and discourages questions. Identify three risks and one safeguard.
Show the worked solution
- Name the information error, not just that the final decision might be bad.
- Separate the dramatic example, ignored trial data and past expenditure.
- Choose a safeguard that would expose evidence or dissent before commitment.
Answer The vivid success story may dominate through availability; ignoring trial data is an omission; and continuing because of money already spent is sunk-cost bias. Discouraging questions may be a groupthink symptom. An independent review using pre-set success criteria and a protected dissenting view could test the plan before further spending.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
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 committee keeps a plan after its data were discredited because ‘we have already invested too much’. Classify the errors and rewrite one decision step.
Give me a hint
Identify the evidence problem and the role of past investment separately.
Compare my reasoning
- Continuing to use discredited evidence is belief perseverance, a sin of commission.
- Continuing because of money already spent is sunk-cost bias, also a sin of commission.
- Before choosing, ask an independent reviewer to check current evidence against criteria agreed in advance.
There are two commission errors: belief perseverance and sunk-cost bias. The committee should assess the plan’s future costs and likely outcomes using current evidence, not try to justify past spending.
Look for these in your work
- Both subtypes named
- Evidence error distinguished from sunk cost
- Safeguard changes the decision process
A group says a detailed candidate is more likely to be an engineer and an activist than simply an engineer. Identify the imprecision error and correct the probability comparison.
Give me a hint
Compare the event ‘engineer and activist’ with the broader event ‘engineer’.
Compare my reasoning
- The detailed profile may feel representative, but the combined event is a subset of the engineer event.
- A subset cannot have a greater probability than the set containing it.
- The group should test the base rates and compare each event explicitly instead of relying on resemblance.
This is conjunction bias. ‘Engineer and activist’ cannot be more likely than ‘engineer’ because every person in the combined category is also in the broader category. Check base rates rather than the profile’s vividness.
Look for these in your work
- Conjunction bias identified
- Subset relationship explained
- Base-rate check proposed
Your team is choosing a school safety procedure. Design two steps that reduce groupthink and two checks for Forsyth-style decision errors.
Give me a hint
Include independent input before the meeting and a structured check for missed or misused information.
Compare my reasoning
- Ask members to submit initial views independently; the chair shares their view only after discussion.
- Assign a critical reviewer and invite someone with relevant external expertise.
- List evidence that could disconfirm the preferred plan and check relevant base-rate or incident data.
- Record sunk costs separately from future costs, and request a second review before adoption.
Independent first responses, a critical reviewer and outside expertise reduce pressure for conformity. A disconfirming-evidence checklist and base-rate review target omission and confirmation errors; a future-cost review counters sunk-cost bias. These controls improve scrutiny but do not guarantee the safest decision.
Look for these in your work
- At least two groupthink safeguards
- Relevant information checked
- At least one commission/omission/imprecision error targeted
Common mistakes
- Treating Tuckman’s stages as an inevitable straight line
- Treating Belbin roles as fixed personality types or job assignments
- Inferring groupthink from a poor decision without evidence about pressure and discussion
- Confusing sins of commission with omission: using discredited or irrelevant information versus failing to use relevant information
- Calling a shortcut imprecision without explaining the heuristic and how it distorts this decision
What can you explain now?
How does a sin of commission differ from a sin of omission?
Compare with the explanation
Commission uses information inappropriately, while omission fails to use relevant information.
For example, persisting with disproved evidence is commission; ignoring relevant base-rate evidence is omission.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Name Tuckman and Jensen’s five stages, group Belbin’s nine roles, and classify one commission, omission and imprecision error with an example.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.