Anchoring Bias
The first number a person sees shapes every judgement that follows, even when it is obviously arbitrary.
Definition
Tversky and Kahneman (1974) showed that estimates are pulled towards an initial reference value, and that this happens even when participants know the anchor was generated at random. Adjustment away from the anchor is typically insufficient.
Established research. Originates in published research and has been replicated. The effect is real. Its size in your product still needs measuring.
On this plate
Reach for this when
- Setting any default value.
- Ordering priced or quantified options.
- Designing sliders, steppers and estimates.
Common mistakes
- Fabricated reference prices.
- Defaults optimised against the user.
- Assuming users will adjust away from a bad anchor. They mostly will not.
- Presenting a fabricated original price as an anchor, which is unlawful in many jurisdictions.
Anchors that exist in every product
- The first price shown, whether or not it is the one most people buy.
- Default quantities, durations and tip percentages.
- The highest tier on a pricing page, which anchors the perceived value of the others.
- Sliders, whose starting position anchors the chosen value.
- Estimated times and progress percentages.
- The first result in a list, which anchors judgements of the rest.
Do
- Choose defaults that are genuinely good for the user, since they will mostly be accepted.
- Order options deliberately, aware that the first sets the reference.
- Show real comparison values, such as unit price, when they help judgement.
Do not
- Display a reference price that was never charged.
- Set a default that benefits the business at the user's expense.
- Use a countdown or scarcity anchor that is not real.
Anchors your product sets, whether you meant to or not
| Anchor | What it shapes |
|---|---|
| The first plan shown | What every other plan is judged against |
| A crossed-out original price | Perceived value of the current price |
| The default quantity or tip | What people choose, more than any argument does |
| The first search result | What a good result looks like for the rest of the list |
| The example in a placeholder | Format, length and ambition of what gets entered |
In practice
- i.
Tip presets
PaymentsThe three preset percentages an interface offers become the reference range. Moving them up shifts behaviour, which is why the choice of presets is an ethical decision and not only a layout one.
- ii.
Pricing page ordering
SaaSPresenting the highest tier first changes how the middle tier is perceived. Both orders are legitimate; presenting a tier nobody can buy is not.
- iii.
The placeholder that set the ambition
An anchor nobody designedA goal field with the placeholder Run 5km produced goals clustered around five kilometres. The field was neutral, the example was not, and it was chosen in ten seconds by whoever wrote the form.
Commonly confused with
Close neighbours that get substituted for each other. The difference is stated first, then the condition that picks one over the other.
Framing Effect
Cognitive biasEquivalent descriptions of the same outcome produce different choices.
Key difference
Anchoring is about a number that arrives first and drags every later estimate toward it. Framing is about the same fact described two ways. One is a reference point, the other is wording.
Use Anchoring Bias when
- There is a first number: a price, a range, a default quantity.
- The question is what to show first on a pricing or comparison page.
Use Framing Effect when
- The numbers are fixed and only the wording is in play.
- You are choosing between a gain phrasing and a loss phrasing.
- The ethical question is whether the framing misleads.
Local chart
BIAS·001 · Region I · Grid A2
This entry and the entries it is stated to connect with. Each line is labelled with what the connection means.
Sources
Where a source establishes something narrower than the popular reading of it, the note says so.
- [1]
Judgment under uncertainty: heuristics and biases
A. Tversky and D. Kahneman, Science, 1974
Continue from here
Each link says what the connection is, so you can tell a principle from an alternative from a thing people mix this up with.
Applies when you are designing
Explains
The mechanism underneath these entries.
- Parkinson's LawLAW·013 · Law
- Deceptive PatternsPRIN·011 · Principle
Applied through
Where this shows up as a concrete interface decision.
- ComparisonPAT·006 · Pattern
- IdeationFLOW·008 · Workflow
Check your work
Review passes that test whether this was done properly.
- Design Ethics ChecklistCHK·010 · Checklist
- Ecommerce ChecklistCHK·006 · Checklist
Related concept
Connected closely enough to change how you apply this.
- Decoy EffectBIAS·012 · Cognitive bias
- Default EffectBIAS·004 · Cognitive bias
- Loss AversionBIAS·002 · Cognitive bias
- Choice OverloadPSY·002 · Psychology