Anchoring and adjustment is a psychological heuristic said to influence the way people estimate probabilities intuitively.

According to this heuristic, people start with an implicitly suggested reference point (the "anchor") and make adjustments to it to reach their estimate.

For instance, when asked to guess the percentage of African nation members of the United Nations, people who were first asked "Was it more or less than 45%?" guessed lower values than those who had been asked if it was more or less than 65%. The pattern has held in other experiments for a wide variety of different subjects of estimation.

Others have suggested that anchoring and adjustment affects other kinds of estimates -- like perceptions of fair prices and good deals.

These findings support the contention of some experts in negotiation that participants should begin from extreme initial positions.

The anchoring and adjustment heuristic was first theorized by Amos Tversky and Daniel Kahneman.