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1.2.3 Aspects of behavioural economic theory

Bounded Rationality and Bounded Self-Control Push Choices Away From the Rational Ideal

Definition

Bounded rationality: the idea that people's ability to make fully rational decisions is limited by the information available, the complexity of the choice and the finite time and mental processing power they have, so they often rely on rules of thumb.

  1. Behavioural economics shows that real consumers often depart from the rational model.
  2. Bounded rationality means limited information and computing power stop people fully optimising.
  3. Bounded self-control means people struggle to act on their long-term interests.
  4. These departures are systematic, not just random slips.
Note
  • Bounded rationality limits people's ability to optimise.
  • Bounded self-control limits their ability to act on long-term interests.
  • These departures are systematic and predictable.

Bounded Rationality: Limited Information and Processing Force People to Use Short Cuts

  1. People rarely have full information.
  2. They cannot process every option perfectly.
  3. So they use short cuts rather than full optimisation.
  4. This leads to choices that fall short of the rational ideal.
Example
  • A shopper cannot compare every product on every feature.
  • They rely on a few cues instead.
  • So the choice is good enough rather than optimal.

Bounded Self-Control: People Struggle to Act on Their Long-Term Interests

  1. People often know the long-term best action but do not take it.
  2. Inertia keeps them doing what they already do.
  3. Habit shapes many everyday choices.
  4. So short-term pulls override long-term interests.
Case study
  • Many people mean to save more but never get round to it.
  • The influence of others and the wish to feel valued also sway choices.
  • So real behaviour departs from strict utility maximisation.

These Departures Are Systematic and Predictable, Not Random Slips

  1. These departures follow predictable patterns.
  2. They happen in the same situations for many people.
  3. So they can be studied and even used in policy.
  4. So they are more than occasional mistakes.
Exam technique
  • Define bounded rationality and bounded self-control.
  • Give a reason consumers may not maximise utility.
  • Stress that the departures are systematic.
Common Mistake
  • Do not treat these as occasional mistakes.
  • They are systematic, predictable departures from rationality.

Biases Such as Rules of Thumb, Anchoring, Availability and Social Norms Skew Decisions

  1. Cognitive biases are patterns that lead choices away from the rational prediction.
  2. Rules of thumb, or heuristics, are mental short cuts.
  3. Anchoring is over-reliance on an initial reference value.
  4. The availability bias judges likelihood by how easily examples come to mind.
Note
  • Heuristics are short cuts that can mislead.
  • Anchoring and availability distort judgement.
  • Social norms and herding shape choices.

Each Bias Pushes Choices Away From the Rational Prediction in a Specific Way

  1. Rules of thumb save effort but can give poor answers.
  2. Anchoring ties a decision to an early number.
  3. Availability overweights vivid or recent examples.
  4. Social norms and herding lead people to copy others.
Example
  • A high original price anchors what shoppers think is a bargain.
  • People overestimate rare risks that are easy to recall.
  • Shoppers copy what others are buying.

Firms and Governments Exploit These Biases in Pricing and Policy

  1. Each bias leads to a specific, predictable error.
  2. Firms can use anchoring in pricing.
  3. Governments can use social norms in messaging.
  4. So biases have real decision and policy effects.
Case study
  • A shop shows a high was price to anchor the sale price.
  • A tax letter says most people in your area have paid, using a social norm.
  • So biases are put to practical use.

Limited Computation and Inertia Reinforce Reliance on Short Cuts

  1. Limited computation forces reliance on short cuts.
  2. Inertia keeps people with the default option.
  3. Both push choices away from the rational ideal.
  4. So biases and limits work together.
Exam technique
  • Define each bias precisely.
  • Give a concrete example of the choice it changes.
  • Note the policy or pricing implication.
Common Mistake
  • Do not describe a bias vaguely.
  • Link it to a specific decision or policy implication.

Altruism and Fairness Qualify the Assumption of Narrow Self-Interest

  1. People do not act purely in narrow self-interest.
  2. Altruism means acting to benefit others.
  3. Fairness concerns shape many economic decisions.
  4. These motives qualify the standard rational-agent assumption.
Note
  • Altruism means acting to benefit others.
  • Fairness concerns influence real choices.
  • Both qualify pure self-interest.

Altruism: People Act to Benefit Others Without Direct Reward

  1. People give to charity without direct reward.
  2. They tip even where they will not return.
  3. They volunteer time for others.
  4. So self-interest is not the whole story.
Example
  • Tipping in a restaurant far from home shows altruism.
  • Charitable giving benefits strangers.
  • So people act beyond narrow gain.

Fairness: People Reject and Punish Outcomes They See as Unfair

  1. People care whether an outcome seems fair.
  2. They may reject an unfair offer even at a cost to themselves.
  3. They punish behaviour they see as unfair.
  4. So fairness shapes choices as well as self-interest.
Case study
  • In the ultimatum game, people reject low, unfair offers.
  • They give up money to punish unfairness.
  • So fairness is a documented influence on behaviour.

Models That Ignore Altruism and Fairness Miss Real Behaviour

  1. Pure self-interest cannot explain these choices.
  2. Models that ignore fairness miss real behaviour.
  3. Firms and governments must allow for these motives.
  4. So altruism and fairness belong in economics.
Exam technique
  • Define altruism and fairness.
  • Give an example such as tipping or rejecting an unfair offer.
  • Explain how they qualify pure self-interest.
Common Mistake
  • Do not assume fairness concerns are irrelevant to economics.
  • They are a documented influence on choices.
Self review
  • What is bounded rationality?
  • What is bounded self-control?
  • Define rules of thumb, anchoring and the availability bias.
  • How do social norms influence decisions?
  • Why do altruism and perceptions of fairness qualify the rational-agent assumption?
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Flowchart comparing the rational agent benchmark with behavioural influences such as bounded rationality, heuristics, present bias, loss aversion and social norms, plus policy responses like nudges, defaults, framing and simplification

Traditional microeconomics starts with the rational economic agent. This benchmark assumes people have stable preferences, process available information logically, and choose the option that maximises utility.

Behavioural economics asks why real choices often depart from that benchmark in systematic ways. Psychological, social and emotional influences can affect decisions in markets such as pensions, energy, health and finance.

This does not mean people are irrational all the time. It means economists should also study predictable biases, self-control problems and the design of the choice environment.

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If a product’s price rises, what does the rational consumer model predict, all else equal?

1.2.3 Aspects of behavioural economic theory Revision Guide

  1. A Level
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  3. /1.2.3 Aspects of behavioural economic theory