Behavioural economics and marketing: seven effects, where each belongs, and how to test them

Behavioural economics is the study of how people really decide, which is with shortcuts, habits and feelings, and not by weighing every option. In marketing it gives you a small set of well studied effects you can test on your own pages: anchoring, loss aversion, social proof, defaults, scarcity, the decoy effect and choice overload. This guide explains each one, shows where it belongs in a marketing page, and gives the test that tells you whether it works for your audience.

Where the field comes from

Daniel Kahneman and Amos Tversky published prospect theory in 1979, showing that people weigh losses more heavily than equal gains. Kahneman received the Nobel Memorial Prize in Economic Sciences in 2002, and Richard Thaler received it in 2017 for his work on how psychology shapes economic decisions. Thaler and Cass Sunstein's 2008 book Nudge brought the idea of the nudge to a wide audience: a change in how options are presented that steers a choice without removing any option. Marketers use the same findings, and you can test each effect cheaply.

Seven effects and how to use them

Effect	What happens	Where it fits on a marketing page
Anchoring	The first number a person sees becomes the reference for later ones	Show the full price or the premium plan first so the main plan looks reasonable
Loss aversion	A loss feels larger than the same gain	Frame an offer around what the buyer keeps or avoids losing, for example "keep your discount"
Social proof	People copy what similar people do	Real reviews, customer counts you can source, named logos with permission
Default effect	People tend to accept the pre selected option	Pre select the plan most buyers need, and keep the alternatives visible
Scarcity	Limited supply or time raises perceived value	Use it only where it is true, such as a real stock level or a real end date
Decoy effect	A third option that is clearly worse than one choice makes that choice look better	Pricing tables with three tiers
Choice overload	Too many options make people put off deciding	Cut a menu to the few options that cover most buyers

Anchoring in practice

Buyers rarely know what a service should cost, so they use the first number as a guide. A page that opens with the premium option makes the middle option look moderate. The anchor has to be a real offering. A fake "was" price invites complaints and, in many countries, consumer law applies to reference prices, so check your local rules before using one.

Loss aversion in practice

Compare "Save 20 percent when you join" with "You lose your 20 percent discount if you leave this page empty handed". The second is stronger in tests run by many companies, but only when the loss is real. Free trial wording works the same way: "your saved work stays available for 30 days" speaks to what a person already holds.

Social proof in practice

Specific proof beats general proof. "Rated 4.6 from 212 reviews on a named platform" is better than "loved by customers", and only a number you can source should appear. For a method to gather reviews and case studies you can reuse, see advocate marketing and user generated marketing.

Defaults and the decoy in a pricing table

A typical three tier table has a small plan, a middle plan with a highlighted badge and a large plan. The large plan acts as the anchor and the decoy at once. Choose the pre selected option for the plan that serves the largest group of buyers well, because a default that puts people into the wrong plan gets cancelled later.

The ethics line: nudge, do not trick

The dividing line is whether the buyer would approve if they saw the technique. A pre selected plan that fits most people is a nudge. A pre ticked box that adds an unrelated paid extra, a countdown timer that resets, or a cancel button hidden three screens deep is a dark pattern. Regulators in several countries have acted against dark patterns, and the buyer who feels tricked leaves a review. Use the effects to make a good choice easier, and apply the test of a plain explanation: if you would be embarrassed to explain the design to the customer, change it.

How to test an effect on your own pages

• Pick one page and one effect. A pricing page and the order of the tiers is a good start.
• Write the prediction. For example: "Showing the annual plan first will raise annual plan sign ups."
• Change one thing. If two elements change together you will not know which worked.
• Split traffic evenly between the old and the new version and run the test across full weeks so weekday patterns balance out.
• Measure the end action, such as purchases, and not clicks on the way.
• Keep the winner and log the result, so the next person starts from what you learned. A click rate reading helps: CTR: the definition, the formula and how to read it.

Small sites with little traffic should test big changes, such as a rewritten offer, because small changes need more visitors to detect. Effects found in one study can behave differently with your audience, so your own result outranks any published one.

Questions about behavioural economics in marketing

What is the difference between behavioural economics and psychology?

Psychology studies the mind broadly. Behavioural economics takes findings about judgement and choice and applies them to economic decisions such as pricing, saving and buying.

Which effect is the easiest to start with?

Social proof, since it only needs honest reviews and numbers you already have.

Is scarcity marketing legal?

Real scarcity is. False scarcity, such as a countdown that restarts, is treated as misleading by many consumer regulators, so state only true limits.

Does it work for business to business marketing?

Yes. Business buyers are people too, and defaults, anchors and proof from similar companies all operate in B2B pricing and demos.

How is it different from neuromarketing?

Neuromarketing measures brain responses. Behavioural economics uses observed choices, which you can gather yourself through tests.

What these effects look like when an assistant is the one choosing

Many buyers now put the comparison to ChatGPT, Gemini or Perplexity and receive a short list with reasons. Social proof and anchoring still work, in a new form: the assistant repeats the proof it can find, such as review scores, awards, named customers and published prices, and it quotes the framing used on your pages. A business with clear, sourced figures on its pricing and review pages gets described by those figures. AI Knows Us asks the assistants the comparison questions your buyers ask and reports which businesses are named and what reasons are attached, so you can see whether the proof you built is the proof they repeat.