Almost every smoker says they would like to stop. Far fewer do. This page is about the gap between wanting and doing — and about a graph-reading skill that turns up again and again in HL questions, where you are handed a set of numbers and asked what they actually prove.
📘 What you need to know
Motivation to quit can be intrinsic (I want a different life) or extrinsic (my family nags me, cigarettes cost too much).
Intrinsic motivation predicts change that lasts; extrinsic motivation usually produces change that stops when the pressure stops.
A falling national trend can act as motivation through social norms — if fewer people smoke, smoking stops feeling normal.
A trend graph shows what changed. It never shows why, because it has no control group and no manipulated variable.
When you analyse data in an exam, describe the pattern, use the numbers, then state a conclusion linked to the claim in the question.
Groups do not all move together: prevalence can fall overall while staying much higher in some groups.
Two reasons to quit, two very different endings
Ask a smoker why they want to stop and you will get answers from both columns of Topic 7.1. “My wife will not stop going on about it” is extrinsic. “I do not want to be the person who has to leave every dinner to smoke” is intrinsic — the reason belongs to them.
Both can start a quit attempt. They tend to end differently. Extrinsic pressure has to keep being applied, and life gets in the way: the nagging stops, the price rise gets absorbed, the shocking image on the packet becomes wallpaper. An intrinsic reason is carried around by the person, so it is still there at 11pm on a bad Tuesday.
This is the argument to build an essay around: campaigns are good at starting quit attempts and poor at keeping them going.
Notice that this is self-determination theory doing real work. Change that feels chosen sticks. Change that feels imposed does not. If you can say that sentence about smoking, you can say it about revision, diets and gym memberships too.
Can a falling trend be a motivator?
Here is a subtler idea. Suppose a smoker learns that smoking rates in their country have dropped year after year. Could the number itself motivate them?
There are two routes, and both are worth writing about:
Encouragement. Lots of people managed it, so it is possible. That feeds self-efficacy — the belief that you could do it too.
Social norms. If most people no longer smoke, a smoker is now the odd one out. Conformity pressure, which normally pushes people towards bad habits, is suddenly pushing the other way.
Both are plausible. Neither is proved by the graph, and that is exactly the point an examiner is testing when they hand you one.
Both lines fall, but the gap between them barely closes. Spotting the gap, not just the fall, is what lifts a data answer from adequate to strong.
🧩 How to analyse a graph in four moves
Say what the graph shows. Variables, groups, time period. One sentence.
Use numbers. Quote a start value, an end value, and the size of the change. Numbers are what turns description into analysis.
Compare the groups. Which is higher, and is the gap closing, steady or widening?
State a conclusion linked to the claim in the question — and say what the data cannot tell you.
Worked examples
WORKED EXAMPLE
Analyse the findings above and state a conclusion linked to the claim that knowing prevalence is falling motivates people to quit. [6 marks]
Move 1 — what it shows
Smoking prevalence fell in both groups across the ten years shown.
Move 2 — the numbers
The general population fell from about 20% to 14%, and people with a mental health condition from about 35% to 26%.
Move 3 — compare
Prevalence stayed far higher in the second group throughout, and the gap of roughly 12 percentage points hardly narrowed.
Move 4 — conclusion
The data are consistent with the claim: as smoking became less common it also became less normal, which could motivate quitting through social norms and through seeing that quitting is possible. But the graph cannot show cause — taxes, smoking bans and advertising rules changed over the same period, and the persistent gap suggests awareness alone does not motivate everyone equally.
Description + figures + comparison + judged conclusionSix marks means all four moves. Most lost marks here are lost by describing and stopping.
WORKED EXAMPLE
Explain one limitation of using this graph to draw conclusions about motivation. [3 marks]
The limitation
The graph measures behaviour, not motivation, so it cannot tell us why anyone stopped.
Why it matters
Prevalence could fall because people became motivated, or because smoking became expensive and inconvenient — the numbers look identical either way.
Consequence
Any claim about motivation drawn from this graph is an inference, not a finding, so qualitative data would be needed to support it.
One limitation, fully explainedThe question asks for one. Two half-explained limitations score less than one complete one.
💡 Exam tip
Always quote figures from a source. “It went down” is description; “from 20% to 14%” is analysis.
Use percentage points for a gap between two percentages. It is a small thing that reads as precision.
Say what type of data you have been given (behavioural, self-report, quantitative) — its type carries its own limitations.
Keep one sentence ready: “quantitative data shows the pattern but not the reason”. It fits nearly every source question in this topic.
Do not invent explanations the source does not support. Suggest them as possibilities instead.
⚠ Common mix-up
Reading a downward trend as proof a campaign worked. No control group, no causal claim.
Ignoring the second line. If a graph shows two groups, the comparison is where the marks are.
Confusing prevalence with number of smokers. Prevalence is a proportion; the population size can change too.
Saying “correlation is not causation” and stopping. Name a plausible alternative cause — that is what earns the mark.
Writing an essay when asked for 3 marks. Time spent here is taken from the 15-mark question.
Up next: Motivation as Children Grow Up — how what motivates a person changes between the ages of three and seventeen, and why a reward that delights a toddler insults a teenager.
Want this explained one-to-one?
Book a free session with an experienced IB Psychology tutor and get your trickiest topics made simple.
