Daniel Kahneman Nobel Lecture

ry of choice that completely ignores feelings such as the pain of losses and the

regret of mistakes is not only descriptively unrealistic. It also leads to pre-

scriptions that do not maximize the utility of outcomes as they are actually ex-

perienced – that is, utility as Bentham conceived it (Kahneman, 1994, 2000c;

Kahneman, Wakker, & Sarin, 1997).

4. ATTRIBUTE SUBSTITUTION: A MODEL OF JUDGMENT 

BY HEURISTIC

The first joint research program that Tversky and I undertook was a study of

various types of judgment about uncertain events, including numerical pre-

dictions and assessments of the probabilities of hypotheses. We reviewed this

work in an integrative article (Tversky & Kahneman, 1974), which aimed to

show “that people rely on a limited number of heuristic principles which re-

duce the complex tasks of assessing probabilities and predicting values to sim-

pler judgmental operations. In general, these heuristics are quite useful, but

sometimes they lead to severe and systematic errors.” (p. 1124). The second

paragraph of that article introduced the idea that “the subjective assessment

of probability resembles the subjective assessments of physical quantities such

as distance or size. These judgments are all based on data of limited validity,

which are processed according to heuristic rules.” The concept of heuristic was

illustrated by the role of the blur of contours as a potent determinant of the

perceived distance of mountains. The observation that reliance on blur as a

distance cue will cause distances to be overestimated on foggy days and un-

derestimated on clear days was the example of a heuristic-induced bias. As this

example illustrates, heuristics of judgment were to be identified by the char-

acteristic errors that they inevitably cause. 

Three heuristics of judgment, labeled representativeness, availability and

anchoring, were described in the 1974 review, along with a dozen systematic

biases, including non-regressive prediction, neglect of base-rate information,

overconfidence and overestimates of the frequency of events that are easy to

recall. Some of the biases were identified by systematic errors in estimates of

known quantities and statistical facts. Other biases were identified by system-

atic discrepancies between the regularities of intuitive judgments and the

principles of probability theory, Bayesian inference or regression analysis.

The article defined the so-called “heuristics and biases approach” to the study

of intuitive judgment, which has been the topic of a substantial research lit-

erature (Kahneman, Slovic, & Tversky, 1982; Gilovich, Griffin, & Kahneman,

2002) and has also been the focus of substantial controversy. 

Shane Frederick and I recently revisited the conception of heuristics and

biases, in the light of developments in the study of judgment and in the

broader field of cognitive psychology in the intervening three decades

(Kahneman & Frederick, 2002). The new model departs from the original

formulation of heuristics in three significant ways: (i) it proposes a common

process of attribute substitution to explain how judgment heuristics work; (ii)

it extends the concept of heuristic beyond the domain of judgments about

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uncertain events; (iii) it includes an explicit treatment of the conditions un-

der which intuitive judgments will be modified or overridden by the moni-

toring operations associated with System 2. 

Attribute substitution

The 1974 article did not include a definition of judgmental heuristics.

Heuristics were described at various times as principles, as processes, or as

sources of cues for judgment. The vagueness did no damage, because the re-

search program focused on a total of three heuristics of judgment under un-

certainty, which were separately defined in adequate detail. In contrast,

Kahneman and Frederick (2002) offered an explicit definition of a generic

heuristic process of attribute substitution: A judgment is said to be mediated by

a heuristic when the individual assesses a specified target attribute of a judg-

ment object by substituting a related heuristic attribute that comes more readi-

ly to mind. This definition elaborates a theme of the early research, that people

who are confronted with a difficult question sometimes answer an easier 

one instead. Thus, a person who is asked “What proportion of long-distance

relationships break up within a year?” may answer as if she had been asked

“Do instances of swift breakups of long-distance relationships come readily to

mind?” This would be an application of the availability heuristic. A respon-

dent asked to assess the probability that team A will beat team B in a basket-

ball tournament may answer by mapping an impression of the relative

strength of the two teams onto the probability scale (Tversky & Koehler,

1994). This could be called a “relative strength heuristic”. In both cases, the

target attribute is low in accessibility and another attribute, which is (i) relat-

ed to the target, and (ii) highly accessible, is substituted in its place.

The word ‘heuristic’ is used in two senses in the new definition. The noun

refers to the cognitive process, and the adjective in ‘heuristic attribute’ speci-

fies the substitution that occurs in a particular judgment. For example, the

representativeness heuristic is defined by the use of representativeness as a

heuristic attribute to judge probability. The definition excludes anchoring ef-

fects, in which judgment is influenced by temporarily raising the accessibility

Figure 7.

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