Cognition, 49 (1993) 11-36
0010-0277/93/506.00 © 1993 - Elvier Science Publishers B.V. All rights rerved.
Reason-bad choice
Eldar Shafir*'a, Itamar Simonson b, Amos Tversky b
avastinDepartment of .Psychology, Princeton University, Princeton, NJ 08544, USA
Department of Psychology, Graduate School of Business, Stanford University, Stanford, CA 94305, USA
Abstract
This paper considers the role of reasons and arguments in the making of decisions. It is propod that, when faced with the need to choo, decision makers often ek and construct reasons in order to resolve the conflict and fustify their choice, to themlves and to others. Experiments that explore and manipulate the role of reasons are reviewed, and other decision studies are interpreted from this perspec-tive. The role of reasons in decision making is considered as it relates to uncertainty, conflict, context effects, and normative decision rules.
The result is that peculiar feeling of inward unrest known as indecision. Fortunately it is too familiar to need description, for to describe it would be impossible. As long as it lasts, with the various objects before the attention, we are said to deliberate: and when finally the original suggestion either prevails and makes the movement take place, or gets definitively quenched by its antagonists, we are said to decide. . . in favor of one or the other cour. The reinforcing and inhibiting ideas meanwhile are termed the reasons or motives by which the decision is brought about.
William James (1890/1981)
My way is to divide half a sheet of paper by a line into two columns; writing over the one Pro, and over the other Con. Then, during three or four days' consideration, I put down under the different' heads shbjt Hints Of the different motives, that at different times occur to me for or against the measure. When I have thus got them all together in one view, 1 endeavor to estimate the respective ·weights. . .find at length where the balance lies. . .And, though the weight of reasons cannol· be taken with the precision of algebraic quantities, yet,.when each is thus considered, parately and
This rearch was supported by US Public Health Service Grant No! 1-R29-MH46885 from the National Institute of Mental Health, by Grant No. 89-0064 from the Air Force Office of Scientific Re
arch and by Grant No. SES-9109535 from the National Science Foundation. The paper was partially prepared while the first author participated in a Summer Institute on Negotiation and Dispute Resolution at the Center for Advanced Study in the Behavioral Sciences, and while the cond author was at the University of California, Berkeley. Funds for support of the Summer Institute were provided by the Andrew W. Mellon Foundation. We thank Robyn Dawes for helpful comments on an earlier draft.
Corresponding author.
12 Shafir et αϊ. / Cognition 49 (1993) 11-36
comparatively, and the whole matter lies before me, I think I can judge better, and am less liable to make a rash step; and in fact I have found great advantage for this kind of equation, in what may be called m oral or prudential algebra.
Benjamin Franklin, 1772 (cited in Bigelow, 1887)
Introduction
The making of decisions, both big and small, is often difficult becau of uncertainty and conflict. We
are usually uncertain about the exact conquences of our actions, which may depend on the weather or the state of the economy, and we often experience conflict about how much of one attribute (e.g., savings) to trade off in favor of another (e.g., leisure). In order to explain how people resolve such conflict, students of decision making have traditionally employed either formal models or reason-bad analys. The formal modeling approach, which is commonly ud in economics, management science, and decision rearch, typically associates a numerical value with each alternative, and characterizes choice as the maximization of value. Such value-bad accounts include normative models, like expected utility theory (von Neumann & Morgenstern, 1947), as well as descriptive models, such as prospect theory (Kahneman & Tversky, 1979). An alternative tradition in the study of decision making, characteristic of scholarship in history and the law, and typical of political and business discour, employs an informal, reason-bad analysis. This approach identifies various reasons and arguments that are purported to enter into and influence decision, and explains choice in terms of the balance of reasons for and against the various alternatives. Examples of reason-bad analys can be found in studies of historic presidential decisions, such as tho taken during the Cuban missile crisis (e.g., Allison, 1971), the Camp David accords (Telhami, 1990), or the Vietnam war (e.g., Herman, 1982; Betts & Gelb, 1979). Furthermore, reason-bad analys are commonly ud to interpret "ca studies" in business and law schools. Althoug
h the reasons invoked by rearchers may not always correspond to tho that motivated the actual decision makers, it is generally agreed that an analysis in terms of reasons may help explain decisions, especially in contexts where value-bad models can be difficult to apply.
Little contact has been made between the two traditions, which have typically been applied to different domains. Reason-bad analys have been ud primarily to explain non-experimental data, particularly unique historic, legal and political decisions. In contrast, value-bad approaches have played a central role in experimental studies of preference and in standard economic analys. The two approaches, of cour, are not incompatible: reason-bad accounts may often be translated into formal models, and formal analys can generally be paraphrad as reason-bad accounts. In the abnce of a comprehensive theory of choice,
Shafir et al. I Cognition 49 (1993) 11-36 13 both formal models and reason-bad analys may contribute to the understand-ing of decision making.
Both approaches have obvious strengths and limitations. The formal, value-bad models have the advantage of rigor, which facilitates the derivation of testable implications. However, value-bad models are difficult to apply to complex, real world decisions, and they often fail to capture significant
aspects of people's deliberations. An explanation of choice bad on reasons, on the other hand, is esntially qualitative in nature and typically vague. Furthermore, almost anything can be counted as a "reason", so that every decision may be rationalized after the fact. To overcome this difficulty, one could ask people to report their reasons for decision. Unfortunately, the actual reasons that guide decision may or may not correspond to tho reported by the subjects. As has been amply documented (e.g., Nisbett & Wilson, 1977), subjects are sometimes unaware of the preci factors that determine their choices, and generate spurious explana-tions when asked to account for their decisions. Indeed, doubts about the validity of introspective reports have led many students of decision making to focus exclusively on obrved choices. Although verbal reports and introspective accounts can provide valuable information, we u "reasons" in the prent article to describe factors or motives that affect decision, whether or not they can be articulated or recognized by the decision maker.
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man or muppetDespite its limitations, a reason-bad conception of choice has veral attractive features. First, a focus on reasons ems clor to the way we normally think and talk about choices. When facing a difficult choice (e.g., between schools, or jobs) we try to come up with reasons for and against each option - we do not normally attempt to estimate their overall values. Second, thinking of choice as gu
ided by reasons provides a natural way to understand the conflict that characterizes the making of decisions. From the perspective of reason-bad choice, conflict aris when the decision maker has good reasons for and against each option, or conflicting reasons for competing options. Unlike numerical values, which are easy to compare, conflicting reasons may be hard to reconcile. An analysis bad on reasons can also accommodate framing effects (Tversky & Kahneman, 1986) and elicitation effects (Tversky, Sattath, & Slovic, 1988), which show that preferences are nsitive to the ways in which options are described (e.g., in terms of gains or loss), and to the methods through which preferences are elicited (e.g., pricing versus choice). The findings, which are puzzling from the perspective of value maximization, are easier to interpret if we assume that different frames and elicitation procedures highlight different aspects of the options and thus bring forth different reasons to guide decision. Finally, a conception of choice bad on reasons may incorporate comparative considera-tions (such as relative advantages, or anticipated regret) that typically remain outside the purview of value maximization.
In this article, we explore the logic of reason-bad choice, and test some
14Shafir et al. I Cognition 49 (1993) 11-36
specific hypothes concerning the role of reasons in decision making. The article proceeds as follows. Section 1 considers the role of reasons in choice between equally attractive options. Section 2 explores differential reliance on reasons for and against the lection of options. Section 3 investigates the interaction between high and low conflict and people's tendency to ek other alternatives, whereas ction 4 considers the relation between conflict and the addition of alternatives to the choice t. Section 5 contrasts the impact of a specific reason for choice with that of a disjunction of reasons. Section 6 explores the role that irrelevant reasons can play in the making of decisions. C oncluding remarks are prented in ction 7.
1. C hoice between equally attractive options
pep小学英语四年级下册教案mendioHow do decision makers resolve the conflict when faced with a choice between two equally attractive options? To investigate this question, Slovic (1975) first had subjects equate pairs of alternatives, and later asked them to make choices between the equally valued alternatives in each pair. One pair, for example, were gift packages consisting of a combination of cash and coupons. For each pair, one component of one alternative was missing, as shown below, and subjects were asked to determine the value of the missing component that would render the two alternatives equally attractive. (In the following example, the value volunteered by the subject may be, say, $10).
Cash
validationCoupon book worth Gift package A
$32
日语 新年快乐Gift package В
$20
$18
A week later, subjects were asked to choo between the two equated alternatives. They were also asked, independently, which dimension - cash or coupons - they considered more important. Value-bad theories imply that the two alternatives - explicitly equated for value - are equally likely to be lected. In contrast, in the choice between gift packages above, 88% of the subjects who had equated the alternatives for value then proceeded to choo the alternative that was higher on the dimension that the subject considered more important.
As Slovic (1975, 1990) suggests, people em to be following a choice mechanism that is easy to ex
plain and justify: choosing according to the more important dimension provides a better reason for choice than, say, random lection, or lection of the right-hand option. Slovic (1975) replicated the above pattern in numerous domains, including choices between college applicants, auto tires, baball players, and routes to work. (For additional data and a discussion of elicitation procedures, e Tversky et al., 1988.) All the results were consistent with the hypothesis that people do not choo between the equated alternatives at
Shafir et al. I Cognition 49 (1993) 11-36 15 random. Instead, they resolve the conflict by lecting the alternative that is superior on the more important dimension, which ems to provide a compelling reason for choice.
2. Reasons pro and con
Consider having to choo one of two options or, alternatively, having to reject one of two options. Under the standard analysis of choice, the two tasks are interchangeable. In a binary choice situation it should not matter whether people are asked which option they prefer, or which they would reject. Becau it is the options themlves that are assumed to matter, not the way in which they are described, if people prefer the first they will reject the cond, and vice versa.
As suggested by Franklin's opening quote, our decision will depend partially on the weights we assign to the options' pros and cons. We propo that the positive features of options (their pros) will loom larger when choosing, whereas the negative features of options (their cons) will be weighted more heavily when rejecting. It is natural to lect an option becau of its positive features, and to reject an option becau of its negative features. To the extent that people ba their decisions on reasons for and against the options under consideration, they are likely to focus on reasons for choosing an option when deciding which to choo, and to focus on reasons for rejecting an option when deciding which to reject. This hypothesis leads to a straightforward prediction: consider two options, an enrich ed option, with more positive and more negative features, and an impoverish ed option, with fewer positive and fewer negative features. If positive features are weighted more heavily when choosing than when rejecting and negative features are weighted relatively more when rejecting than when choosing, then an enriched option could be both chon and rejected when
compared to an impoverished option. Let P
c an
d P
soulmate是什么意思r
lns
denote, respectively, the
percentage of subjects who choo and who reject a particular option. If choosing and rejecting are complementary, then the sum Р
с
+ Р, should equal 100. On the
xamenother hand, according to the above hypothesis, P
c + P
r
should be greater than 100
for the enriched option and less than 100 for the impoverished option. This pattern was obrved by Shafir (1993). C onsider, for example, the following problem which was prented to subjects in two
versions that differed only in the bracketed questions. One half of the subjects received one version, the other half received the other. The enriched option appears last, although the order prented to subjects was counterbalanced.
Problem 1 (n = 170):
Imagine that you rve on the jury of an only-child sole-custody ca following
