The classic demonstration
In a well-known 1974 study, people watched a wheel of fortune land on a number. They then estimated the percentage of African countries in the United Nations. Those who saw a higher number gave higher estimates, even though the wheel had no connection to the question. Anchoring has since been studied in pricing, negotiation and legal judgments.
Why it happens
One account is that people start at the anchor and adjust away from it, but stop too soon. Another, selective accessibility, suggests the anchor brings to mind information consistent with it. Both mechanisms may operate, with adjustment more prominent when people generate the anchor themselves.
Limits
The basic effect in numerical estimates has proved robust across large replication projects. Other claims, such as those about completely incidental anchors like a person's social security digits influencing what they would pay, have been weaker when retested. Experts are not immune, although knowledge may reduce the size of the effect.
Further reading
- Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185, 1124-1131.
- Epley, N., & Gilovich, T. (2006). The anchoring-and-adjustment heuristic: Why the adjustments are insufficient. Psychological Science, 17, 311-318.
- Furnham, A., & Boo, H. C. (2011). A literature review of the anchoring effect. Journal of Socio-Economics, 40, 35-42.