Anchoring Bias: Why the First Number Pulls Your Estimate
A number can become a reference point before you have any reason to trust it. Spin a wheel, make an estimate, and see how far the random start pulled you. Then learn where anchors hide in prices, deadlines and negotiations, and how to build an estimate that deserves weight.
BySeph Fontane Pennock
Reviewed byMichael Callans, MSW
What is anchoring bias?
Anchoring bias is the tendency to give a starting value too much influence when making a judgment. A number you encounter first can pull a later estimate toward it, even when that number tells you little about the question. The pattern is called the anchoring effect. A starting point can be useful, but its influence should depend on the evidence behind it.
Anchoring bias examples
- A sale price: a lamp reduced from $160 to $90 feels cheap, before you compare what similar lamps actually sell for.
- A time estimate: someone casually says a task takes two hours, and the team's estimates cluster around that figure before anyone lists the work.
- A random number: a wheel result becomes a reference point for an unrelated factual estimate.
These are illustrations of possible anchoring, not enough evidence to label a particular person's decision.
The study behind the wheel
In their 1974 paper, Tversky and Kahneman described asking people to compare an unknown percentage with a wheel-generated number before estimating the percentage itself. Groups given different starting numbers produced different median estimates, even though the wheel supplied no relevant information. Read the original report on judgment under uncertainty.
0 / 100 insight points0 / 5 stamps
20 points for completing the experiment, 10 for each of eight checks. Retries earn full points. First-attempt accuracy is separate.
Questions about anchoring bias
What is anchoring bias?
Anchoring bias is giving a starting value too much influence when making a judgment. An estimate can be pulled toward an initial number even when that number is irrelevant. The anchoring effect names the pattern; an anchoring heuristic is a shortcut that uses a starting point.
What is an example of anchoring bias?
A lamp marked down from $160 to $90 may seem inexpensive because $160 has become the reference point. If comparable lamps sell for $60, the discount alone is a poor guide to value. The sale tag is an anchor, not proof that the buyer is biased.
What is anchoring and adjustment bias?
One explanation is that people start from an initial value and adjust away from it, but stop too soon. Another explanation is selective accessibility: considering an anchor makes information consistent with it easier to bring to mind. Different tasks may involve different processes.
How does anchoring bias differ from confirmation bias?
Anchoring concerns the influence of a starting point on a judgment. Confirmation bias concerns favoring evidence that supports an existing belief. They can overlap when considering an anchor leads someone to focus on facts that fit it.
How can you reduce anchoring bias?
Try forming an independent estimate before seeing a proposed number, checking relevant comparison data, and considering evidence that would support a substantially different value. These are useful habits, not a guarantee of immunity. A well-supported first number can still be informative.
Sources
- Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185(4157), 1124–1131.
- Strack, F., & Mussweiler, T. (1997). Explaining the enigmatic anchoring effect: Mechanisms of selective accessibility. Journal of Personality and Social Psychology, 73(3), 437–446.
- Furnham, A., & Boo, H. C. (2011). A literature review of the anchoring effect. The Journal of Socio-Economics, 40(1), 35–42.
- U.S. Geological Survey. How much water is there on Earth? Water Science School.
Cite this source
Psychology.com. (2026, September 16). Anchoring Bias. Psychology.com. https://psychology.com/courses/anchoring-bias
More mini courses
- Confirmation Bias (12 to 15 minutes): Try the 2-4-6 number puzzle, inspect your test choices, and learn to look for evidence that could change your mind.
- Hindsight Bias (12 to 15 minutes): Make five predictions, then compare your remembered answers with the record. Learn why a known ending can make uncertainty disappear.
- The Availability Heuristic (12 to 15 minutes): Compare your frequency estimates with real counts, distinguish recall from evidence, and practice a simple base-rate check.