IB Psychology SLTopic 3 — Group BehaviourPaper 1 & 2Key study~8 min read
Commitment as a Compliance Technique
You agreed to look after your niece for an hour. Somehow you are now on hour six with two children and a broken biscuit tin. Nobody forced you. That is the point — commitment works precisely because it feels like your own idea.
📚 What you need to know
Compliance is saying yes to a request or an offer.
Compliance techniques are not subliminal. People usually know they are being asked — the technique is just subtle enough that it still works.
Commitment means getting someone to agree to something small first, so they are more likely to agree to something bigger later.
It needs active, willing participation. Signing your own name does something that being handed a leaflet does not.
Prosocial behaviour is behaviour that benefits other people or society, and commitment is one of the main tools used to encourage it.
The study you need is Dickerson et al. (1992), on shower length in a university swimming pool.
Why a small yes leads to a bigger yes
People like to feel consistent. Once you have said out loud that you care about something, refusing to act on it feels uncomfortable — not because anyone is watching, but because it makes you look bad to yourself. Commitment techniques hijack that feeling.
The key word is active. Reading a poster about saving water does very little. Signing that poster does a lot more, because now you have made a public statement and your name is on it. You are no longer someone who happened to see a message; you are someone who agreed with it.
The technique fails if the first step is passive. Being shown a message is not a commitment; agreeing to it is.
Salespeople use this constantly. ‘Just take the free trial’ is not generosity — it is step one. Once you have set the account up yourself, cancelling feels like undoing your own work.
Commitment and prosocial behaviour
Prosocial behaviour is anything that helps other people or society: recycling, donating, giving up a seat, using less water. Governments, schools and companies all want more of it, and commitment is one of the cheapest ways to get it.
Governments run campaigns asking people to pledge to recycle or cut energy use.
Schools ask pupils to sign anti-bullying charters at the start of term.
Companies attach themselves to a value and invite customers to sign up to it.
Making the commitment public also builds a sense of shared responsibility. If everyone signed, then not acting means letting the group down, not just yourself.
Key study: Dickerson et al. (1992)
Part of the study
What happened
Aim
To test whether making a prior commitment leads to real prosocial behaviour, not just good intentions.
Participants
80 female students at a college in Santa Cruz, California, all competitive swimmers. Opportunity sample.
Procedure
A female confederate stopped swimmers on their way from the pool to the showers. There were four conditions: questionnaire only about their water use; poster only, which they were asked to sign; both; and a control group who were not approached at all. A second confederate, already in a shower cubicle, timed how long each swimmer showered.
Results
Swimmers who did both the questionnaire and the poster took the shortest showers. The control group took the longest by a clear margin.
Conclusion
Making a prior commitment to save water actually reduced water use. Commitment changed behaviour, not just opinions.
Notice that one step on its own barely moved the numbers. Two commitments stacked together made the difference.
Do not memorise all four numbers to two decimal places. Learn the pattern: control highest, both-together lowest, the two single conditions in between and close to each other. That pattern is what the marks are for.
Evaluating the study
What is strong about it
The participants were naive — they had no idea they were in a study, so there were no demand characteristics. They were simply showering after a swim, which gives high ecological validity.
It measured real behaviour, not a questionnaire about intentions. That is rare and it is the study’s best feature.
The four conditions were carefully separated, so you can see what each part of the technique contributed.
What is weaker about it
Only one confederate timed the showers. She may have missed the start or the end, and there was no second timer to check against, which weakens reliability.
All 80 participants were female students at one American college, so generalising is risky.
It only measured one shower. Whether the effect lasted a week or a month is unknown.
Link to concepts
Causality: this is a field experiment designed like a lab study. The independent variable was properly manipulated across four conditions, which is unusual outside a lab and lets the researchers claim a causal effect.
Responsibility: there are real ethical problems. The swimmers were deceived, they could not give informed consent, they had no right to withdraw, and being timed in the shower is a clear invasion of privacy.
EXAM PRACTICE
Explain one compliance technique, with reference to one study. [9]
Step 1: define the technique
Commitment: getting active agreement to a small request so that a larger, matching behaviour becomes more likely.
Step 2: explain why it works
People want to stay consistent with what they have publicly said, so acting against a signed statement feels wrong.
Step 3: the study
Dickerson et al. (1992). 80 female swimmers, four conditions, shower length timed by a hidden confederate.
Step 4: the finding that proves the point
The questionnaire plus poster group showered for the shortest time; the control group the longest.
Step 5: evaluate
Naive participants means high ecological validity, but only one confederate timed the showers, so reliability is questionable.
Technique + mechanism + study + link + evaluationThe mechanism line is what separates a 6 from a 9. Do not skip it.
💡 Exam tip
Compliance is not conformity. Compliance is a response to a request; conformity is a response to group pressure. Examiners see this confused constantly.
Stress the word active. The whole technique rests on the person doing something themselves.
The ethics of Dickerson are an easy source of evaluation marks — deception, consent, privacy, right to withdraw. Four points from one study.
If a question asks about prosocial behaviour, use this study. It measures a prosocial act directly.
Say ‘field experiment’, and add that the IV was manipulated. That shows you know why it is unusual.
⚠ Common mix-up
Calling the technique subliminal. Participants were unaware of the study, but they were fully aware of signing a poster. That is not subliminal.
Saying condition 2 was the most effective. It was condition 3, questionnaire and poster together.
Forgetting the control group. Without it you cannot say the technique worked at all.
Describing this as a lab experiment. It happened in a real shower block. It is a field experiment.
Claiming the swimmers consented. They did not, and that is one of the study’s biggest ethical problems.
Up next: Why People Conform to a Group — the two very different reasons people go along with everyone else, and the famous line-judging study that exposed them.
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