Anchoring effect or focalism is a cognitive bias that describes the common human tendency to rely too heavily on the first piece of information offered (the “anchor”) when making decisions. It’s the tendency to compare and contrast only a limited set of items. It can also be known as the relativity trap.
During decision making, anchoring occurs when individuals use an initial piece of information to make subsequent judgments. Once an anchor is set, other judgments are made by adjusting away from that anchor, and there is a bias toward interpreting other information around the anchor.
For example, the initial price offered for a used car sets the standard for the rest of the negotiations, so that prices lower than the initial price seem more reasonable even if they are still higher than what the car is really worth. See also focusing effect.
Another example is an item at the store that’s on sale; we tend to see (and value) the difference in price, but not the overall price itself. This is why some restaurant menus feature very expensive entrees, while also including more (apparently) reasonably priced ones. It’s also why, when given a choice, we tend to pick the middle option — not too expensive, and not too cheap.