Distinction bias

Distinction bias, a concept of decision theory, is the tendency to view two options as more distinctive when evaluating them simultaneously than when evaluating them separately.

One writer has presented what he called "a simplistic view" of distinction bias: "When I ask you if you would like an apple, you may say 'Yes.'...So I place an apple before you and you begin to eat it. And you are happy. But what if I were to place two apples on the table – one was the one you would have have happily eaten and the other which is slightly fresher looking. You will choose the fresher apple and eat it and be happy....But, if I asked you, 'would you have enjoyed eating that other apple,' you would likely say 'No.' Even though in our alternate no-choice reality you were perfectly happy with the apple." Moreover, if presented with five apples on a table, "you might take a few minutes to examine each apple so that you would be sure you had the best one," even though the time spent making that decision would be more or less wasted. The reason for this is that distinction bias "causes us to over-examine and over-value the differences between things as we scrutinize them."

The concept of the distinction bias was advanced by Christopher K. Hsee and Jiao Zhang of the University of Chicago as an explanation for differences in evaluations of options between joint evaluation mode and separate evaluation mode (2004). Evaluation mode is a contextual feature in decision making. Joint evaluation mode is when options are evaluated simultaneously, and separate evaluation mode is when each option is evaluated in isolation (e.g., Hsee, 1998; Hsee & Leclerc, 1998). Research shows that evaluation mode affects the evaluation of options, such that options presented simultaneously are evaluated differently from the same options presented separately.

Hsee and Zhang (2004) offered a number of potential explanations for this change in preferences from joint evaluation to separate evaluation, including the distinction bias. The distinction bias suggests that comparing two options, as done in joint evaluation, makes even small differences between options salient. In other words, viewing options simultaneously makes them seem more dissimilar than when viewing and evaluating each in isolation.

"When people make predictions or choices," explained Hsee and Zhang in their 2004 paper, "they are often in the joint evaluation (JE) mode; when people actually experience an event, they are often in the single evaluation (SE) mode. The 'utility function' of an attribute can vary systematically between SE and JE. When people in JE make predictions or choices for events to be experienced in SE, they often resort to their JE preferences rather than their SE preferences and overpredict the difference that different values of an attribute (e.g., different salaries) will make to their happiness in SE. This overprediction is referred to as the distinction bias."

...
Wikipedia