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.
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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."
Hsee and Zhang
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."
Examples and applications
For example, when televisions are displayed next to each other on the sales floor, the difference in quality between two very similar, high-quality televisions may appear great. A consumer may pay a much higher price for the higher-quality television, even though the difference in quality is imperceptible when the televisions are viewed in isolation. Because the consumer will likely be watching only one television at a time, the lower-cost television would have provided a similar experience at a lower cost.
The same calculus can apply when one is choosing between a cheaper store-brand food product and a more expensive brand-name product. In many cases, the difference in taste between the two products would not be worth the difference in price. If the products were sampled in isolation, the difference in taste would be unnoticeable or negligible; consequently, the difference in price, not the difference in taste, ought to determine which choice the consumer makes. In 2010, a magazine asked consumers to try 12 brands of baked beans. Branston won the taste test, followed by Asda, Morrisons, and Heinz. The Morrisons beans, in other words, were preferred over the Heinz beans, even though, as it happened, they were half the price.
One writer has discussed the distinction bias in connection with such matters as choosing a job or a house. When making a choice between "an interesting job that pays $60,000 a year" and "a boring job that pays $70,000 a year" or a choice between two equally priced houses, one of them larger but farther from work, the average individual is likely to make false assumptions – for example, "that $70,000 will make us feel exactly one-sixth better than $60,000, or that 4,000 square-foot house is one-third better than a 3,000 square-foot house." In reality, "on average, we don't actually feel one-sixth better having the extra money or one-third better having the extra space". The more sensible approach, the writer advises in accordance with the research of Hsee and Zhang, is "to avoid comparing two jobs, or houses, directly". Instead, "consider each job, or house, individually. Try to make an overall assessment of each one on its own, and then compare your assessments. This way you are much more likely to make a choice that accurately predicts your future experience."
Further studies
In 2009, Margaret E. Brooks, Ashley M. Guidroz, and Madhura Chakrabarti reported on two studies in which they had examined the reactions of job applicants to alternative approaches to diversity in employment decisions. The applicants preferred the so-called holistic approaches, and the magnitude of their preference was considerably greater when both approaches were evaluated simultaneously. The researchers found that the results, which they viewed as important for "applicant reactions research, human resource decision making, and policy formation", were consistent with distinction bias.