Consumer choices can reflect habits, social influences and framing as well as calculated utility.
Must know
- The rational model assumes utility maximisation.
- Behavioural influences can change choices.
- Equivalent information can produce different responses when framed differently.
Must know definitions
Utility: the total satisfaction received from consuming a good or service.
Rational decision-making: making decisions that maximise utility or benefit.
Homo Economicus: the theoretical rational consumer who always maximises utility.
Heuristics: mental shortcuts or rules of thumb that simplify decision-making but can lead to irrational choices.
Behavioural economics: uses psychology to explain why consumers do not always act rationally.
Framing effect: the way equivalent information is presented influences perception and choice.
Diminishing marginal utility: each additional unit consumed provides less satisfaction than the previous one.
Explain and apply
Mechanism in brief: A default makes one option easier to select or retain. Inertia can therefore change take-up, but the effect depends on whether people notice the default and can readily choose an alternative.
Distinguish: An unusual choice is not automatically irrational; positive framing does not universally cause risk-taking.
Use the extract: Identify the default, framing, habit or social influence actually described; explain which choice it changes.
Assumptions of rationality in decision-making
Rational decision-making means making decisions that maximise utility or benefit.
- Supply and demand models assume consumers and firms are economic agents seeking to maximise their own utility.
- Consumers aim to maximise the utility (satisfaction) gained from purchasing goods and services.
- Firms aim to maximise profit from selling them.
- This rational agent is known as Homo Economicus — a theoretical consumer who always has full information and acts to maximise utility.
| Agent | Aim | Assumption |
|---|---|---|
| Consumer | Maximise utility from consumption | Homo Economicus — always chooses the option giving greatest satisfaction |
| Firm | Maximise profit from selling goods/services | Always chooses the most profitable output/price |
Reasons why consumers may not aim to maximise utility
Behavioural economics uses psychology and evidence from experiments to explain why consumers do not always act rationally, challenging the traditional Homo Economicus assumption.
- Real consumers rely on heuristics — mental shortcuts or rules of thumb (e.g. only buying in a sale) — to cope with imperfect information and limited time, which can lead to irrational choices.
- Decisions are frequently shaped by the influence of others, habit, and the need to feel valued.
Inertia means sticking with the existing choice or default because switching requires effort or attention, even where an alternative might offer higher utility; for example, not switching an expensive energy tariff.
The need to feel valued can influence spending on status goods or products associated with acceptance by a social group. Biases are systematic tendencies in judgement; for example, present bias gives disproportionate weight to immediate benefits relative to future costs.
- Weak numeracy and weak self-control also push consumers away from utility maximisation.
- The way choices are presented — the framing effect — alters decisions independently of the utility on offer.
"irrational" does not mean stupid — it means the choice does not maximise utility, often because information is imperfect or shortcuts are used.
| Reason | Explanation | Example |
|---|---|---|
| Influence of others | Social pressure encourages consumers to copy others' behaviour rather than judge utility independently | Choosing a restaurant with a long queue over an empty one nearby |
| Habitual behaviour | Habits reduce decision-time by removing conscious thought, creating a barrier to considering better alternatives | Continuing to smoke despite knowing the harm; sticking to the same commute |
| Weak computation / self-control | Consumers struggle to apply concepts like diminishing marginal utility and lack self-control, favouring short-term over long-term benefit | Overeating despite less satisfaction per extra unit; procrastinating on pension saving ("I'll start tomorrow") |
| Framing effect | The way information/choices are presented alters perception and decision, independent of the actual utility on offer | Advertising a product as "90% fat free" rather than "10% fat" |
The framing effect occurs when equivalent information presented in different ways leads to different choices. For example, “90% fat free” and “10% fat” describe the same product but can prompt different reactions. The effect depends on the decision context; a positive frame does not universally cause risk-taking.
| Frame | Feeling elicited | Effect on behaviour |
|---|---|---|
| Positive frame | Emphasises a gain or desirable feature | May change perceived attractiveness; the response depends on context |
| Negative frame | Emphasises a loss or undesirable feature | May change perceived attractiveness; the response depends on context |
A behavioural intervention is more persuasive when the barrier is demonstrated in the context. Information or a default may have little effect if affordability is the main constraint; unusual preferences alone do not prove irrationality.
Rapid recap
Rational choice compares expected costs and benefits. Habits, framing, defaults and social influences can change choices without a change in price or income.
Diagram cue: trace the behavioural influence → changed choice.
Related chapters: Unit 1 chapter 8 (p. 25) · Unit 1 chapter 15 (p. 69)