Anchoring Bias: Definition, Causes & How to Reduce It

Once an anchor is established, it becomes difficult for people to adjust their thinking objectively, often leading to poor or limited decisions. The first number, price, belief or assumption acts like a magnet: subsequent reasoning drifts towards it rather than starting from a neutral position. Understanding this mechanism is the first step to designing it out of your judgments, and anchoring bias is a recurring concern across the wider field of research bias.

What Is Anchoring Bias?

Anchoring bias is a cognitive bias that affects judgment and decision-making by causing people to depend excessively on initial information, even when that information is irrelevant, outdated, or incorrect. It belongs to a family of mental shortcuts, or heuristics, that the brain uses to reach conclusions quickly. As with the closely related affect heuristic, the shortcut is efficient most of the time but systematically distorts judgment under certain conditions.

When an anchor is introduced, such as a price, a number, a belief, or an assumption, it shapes how future information is interpreted. Instead of evaluating all available options objectively, decisions are made by adjusting around this anchor, and the adjustment is almost always too small. The result is an estimate that sits much closer to the anchor than the evidence justifies.

The original demonstration is famous. Tversky and Kahneman spun a wheel of fortune rigged to land on either 10 or 65, then asked participants to estimate the percentage of African countries in the United Nations. Those who saw the number 65 gave a median estimate of 45%; those who saw 10 gave a median of 25%. The wheel was obviously random and irrelevant, yet it still moved people’s answers, demonstrating how powerful an arbitrary anchor can be.

This bias plays a major role in:

• Personal decision-making
• Business and finance
• Negotiation and pricing
• Medical diagnosis
• Academic and research processes

Types of Anchors

Anchors can be grouped into two broad types, and recognising which one is operating helps you decide how to counter it:

• External anchors: reference points provided by outside sources, such as price tags, suggested retail prices, initial salary offers, and the first number mentioned in a negotiation.
• Internal anchors: reference points based on beliefs, past experiences, memories, or expectations, such as childhood beliefs, past salary levels, previous exam scores, and prior health diagnoses.

What Are the Causes of Anchoring Bias?

Anchoring bias is not caused by carelessness or low intelligence; it affects experts and novices alike. Two well-documented psychological mechanisms explain why it happens, and understanding them shows why simply “trying harder” rarely removes the effect.

Anchoring and Adjustment

This mechanism explains how people answer questions when they do not know the full correct answer. They start from an available anchor in their mind and then adjust away from it towards what feels reasonable. Because adjusting is mentally effortful, people stop as soon as the estimate enters a plausible range, which is usually well before they reach the accurate value.

The more uncertain or rushed a person is, the smaller the adjustment, and the closer the final answer stays to the anchor. When no further information arrives to correct the anchor, the result is a biased estimate that hovers near the starting point.

Selective Accessibility (Confirmatory Testing)

This mechanism explains how external anchors influence reasoning. When people are given an anchor, they unconsciously test the hypothesis that the anchor is correct and selectively retrieve information consistent with it. This process, called selective accessibility, makes anchor-consistent evidence easier to recall and anchor-inconsistent evidence easier to overlook, which deepens the distortion.

Factors That Strengthen the Effect

Several conditions make anchoring bias stronger and harder to escape:

• Uncertainty: the less you know about the true value, the more weight the anchor carries.
• Time pressure: rushed decisions leave no room for full adjustment.
• Cognitive load: tiredness or distraction reduces the effort available to move away from the anchor.
• Relevance illusion: when an anchor looks plausible, it is trusted even if its source is unreliable.

Anchoring Bias Examples

These real-world examples show how anchoring bias operates across very different settings, from trading floors to restaurant menus.

1. Anchoring Bias in Finance

Anchoring bias is prominent in finance, where investors predict future prices using the current value of an asset. For instance, when people are asked where Apple’s share price will be in three months, they anchor on where the stock trades today and adjust only slightly, even though future prices depend on many other factors. Investors also anchor on the price they originally paid, refusing to sell a falling stock until it returns to that purchase “anchor”.

2. Anchoring Bias in the Workplace

Imagine you are negotiating a pay rise with your manager. Whoever names a figure first sets the anchor that frames the rest of the conversation. If you open with a well-researched number, the final agreement is likely to land nearer your target than if you let the employer set the opening figure.

3. Anchoring Bias in Healthcare Communication

Anchoring can also shape how clinicians communicate. When a doctor asks, “What questions do you have?” rather than “Do you have any questions?”, the wording anchors the patient on the expectation that asking questions is normal, encouraging a more open and honest consultation.

4. Anchoring Bias in Medicine

In clinical diagnosis, anchoring bias significantly influences a physician’s decisions. When a doctor fixes on a single piece of information from an earlier examination, it can introduce information bias that distorts the rest of the diagnostic process. As a result, physicians may ignore later evidence that would lead to a more accurate understanding of the patient’s condition.

5. Anchoring Bias in Negotiation

In any negotiation, the first number presented becomes the anchor around which both parties bargain. Once a starting price is set, offers are adjusted until both sides reach agreement, but the final figure usually remains tethered to that opening anchor, which is why experienced negotiators try to make the first credible offer.

6. Anchoring Bias in Restaurants

Menus are often engineered around anchoring. Placing a very expensive “showcase” dish at the top makes everything beneath it feel reasonably priced, while listing lower-priced items first can create an impression of overall value. Either way, the first price you read anchors your sense of what the meal should cost.

Anchoring Bias in Research

For students and researchers, anchoring bias is more than a curiosity, because it can quietly compromise the credibility of a study. It can creep into the research process at several stages:

• Literature review: the first influential study you read can anchor your interpretation of every paper that follows, so you read later evidence to confirm rather than to test it.
• Hypothesis formation: an initial expectation can anchor the way you frame your research question and the variables you choose to measure.
• Data interpretation: an early result, a pilot finding, or a striking outlier can anchor how you read the full dataset.
• Peer and supervisor feedback: the first comment you receive can disproportionately shape how you revise your work.

Because anchoring distorts how evidence is gathered and weighed, it threatens both the reliability and validity of your conclusions. A study anchored on a flawed assumption can produce results that are internally consistent yet systematically wrong. It is closely related to other measurement and interpretation pitfalls, including regression to the mean, where an unusually high or low first measurement anchors expectations that later, more typical, readings then appear to contradict. Treating anchoring as one of several systematic threats, and reading widely on the topic of research bias, helps you design it out of your methodology.

“In general, these heuristics are quite useful, but sometimes they lead to severe and systematic errors.” — Amos Tversky & Daniel Kahneman, Science (1974)

How to Reduce or Avoid Anchoring Bias

You cannot switch anchoring bias off entirely, because it operates below conscious awareness, but you can build habits and safeguards that limit its influence. The strategies below work in both everyday decisions and formal research, and the table that follows summarises them by setting.

1. Delay the first number. Form your own independent estimate before you look at any reference figure, then compare. This stops an external anchor from contaminating your starting point.
2. Generate multiple anchors. Deliberately consider a high, a low, and a middle estimate. Averaging across several starting points dilutes the pull of any single one.
3. Consider the opposite. Actively ask, “What evidence would prove this anchor wrong?” This counters selective accessibility by forcing anchor-inconsistent information into view.
4. Seek independent data. Gather figures from several credible, unconnected sources rather than building on the first one you find.
5. Slow down high-stakes decisions. Because time pressure strengthens anchoring, scheduling a deliberate pause gives you room to adjust fully.
6. Use blind procedures in research. Where possible, analyse data without knowing prior results or the hypothesis being tested, so early findings cannot anchor your interpretation.
7. Pre-register and document. Recording your method, predictions, and how you cite each reference before you collect data makes it harder to drift towards a convenient anchor afterwards.
8. Invite an outside view. A colleague or supervisor who has not seen your anchor can flag where your reasoning has been pulled off course.

Applying even two or three of these safeguards consistently will measurably improve the objectivity of your judgments. The goal is not to eliminate first impressions, which are often useful, but to stop them from quietly overriding the evidence. For a broader grounding in the systematic errors that affect studies, our hub on research bias sets anchoring alongside the other distortions every researcher should learn to recognise and control.

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