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.
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.
In practice
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.
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.
Sources
Where a source establishes something narrower than the popular reading of it, the note says so.
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
Applied through
Where this shows up as a concrete interface decision.
- ComparisonPattern
- IdeationWorkflow
Check your work
Review passes that test whether this was done properly.
- Design Ethics ChecklistChecklist
- Ecommerce ChecklistChecklist
Related concept
Connected closely enough to change how you apply this.
- Decoy EffectCognitive bias
- Default EffectCognitive bias
- Framing EffectCognitive bias
- Loss AversionCognitive bias
- Choice OverloadPsychology