Daniel Kahneman Nobel Lecture

image of a feminist bank teller more than she resembles a stereotypical bank

teller. However, the reliance on representativeness as a heuristic attribute

yields a pattern of probability judgments that violates monotonicity, and has

been called the ‘conjunction fallacy’ (Tversky & Kahneman, 1983). 

The results shown in Figure 8 are especially compelling because the re-

sponses were rankings. The large variability of the average rankings of both

attributes indicates highly consensual responses, and nearly total overlap in

the systematic variance. Stronger support for attribute-substitution could

hardly be imagined, and it is surprising that this evidence was not acknow-

ledged in subsequent debates about the validity of judgment heuristics. Other

tests of representativeness in the heuristic elicitation design have been equal-

ly successful (Bar-Hillel & Neter, 2002; Tversky & Kahneman, 1982). The

same design was also applied extensively in studies of support theory (Tversky

& Koehler, 1994; for a review see Brenner, Koehler & Rottenstreich, 2002). In

one of the studies reported by Tversky and Koehler (1994), participants rated

the probability that the home team would win in each of 20 specified basket-

ball games, and later provided ratings of the relative strength of the two

teams, using a scale in which the strongest team in the tournament was as-

signed a score of 100. The correlation between normalized strength ratings

and judged probabilities was .99. 

The essence of attribute substitution is that respondents offer a reasonable

answer to a question that they have not been asked. An alternative interpre-

tation that must be considered is that the respondents’ judgments reflect

their understanding of the question they were asked. This may be true in

some situations: it is not unreasonable to interpret a question about the prob-

able outcome of a basketball game as referring to the relative strength of the

competing teams. But the idea that judgments signify a commitment to the

interpretation of the target attribute does not generally hold. For example, it

is highly unlikely that educated respondents have a concept of probability

that coincides precisely with similarity, or that they are unable to distinguish

picture size from object size. A more plausible hypothesis is that an evaluation

of the heuristic attribute comes immediately to mind, and that its associative

relationship with the target attribute is sufficiently close to pass the monitor-

ing of a permissive System 2. Respondents who substitute one attribute for an-

other are not confused about the question that they are trying to answer –

they simply fail to notice that they are answering a different one. And when

they do notice the discrepancy, they either modify the intuitive judgment or

abandon it altogether.

The new heuristics

As illustrated by its use in the interpretation of the visual illusion of Figure 7,

the definition of judgment heuristics by the mechanism of attribute substitu-

tion applies to many situations in which people make a judgment that is not

the one they intended to make. There is no finite list of heuristic attributes.

Kahneman and Frederick (2002) illustrated this conception by a study by

Strack, Martin, and Schwarz (1988), in which college students answered a sur-

469

---

vey that included these two questions: “How happy are you with your life in

general?” and “How many dates did you have last month?”. The correlation

between the two questions was negligible when they occurred in the order

shown, but it rose to 0.66 when the dating question was asked first. The mod-

el of attribute substitution suggests that the dating question automatically

evokes an affectively charged evaluation of one’s satisfaction in that domain

of life, which lingers to become the heuristic attribute when the happiness

question is subsequently encountered. The underlying correlation between

the target and heuristic attributes is surely higher than the observed value of

0.66, which is attenuated by measurement error. The same experimental ma-

nipulation of question order was used in another study to induce the use of

marital satisfaction as a heuristic attribute for well-being (Schwarz, Strack, &

Mai, 1991). The success of these experiments suggests that ad hoc attribute

substitution is a frequent occurrence.

The idea of an affect heuristic (Slovic et al., 2002) is probably the most im-

portant development in the study of judgment heuristics in the last decades.

There is compelling evidence for the proposition that every stimulus evokes

an affective evaluation, which is not always conscious (see reviews by Zajonc,

1980, 1997; Bargh, 1997). Affective valence is a natural assessment, and there-

fore a candidate for substitution in the numerous responses that express atti-

tudes. Slovic and his colleagues (Slovic et al., 2002) discuss how a basic affec-

tive reaction can be used as the heuristic attribute for a wide variety of more

complex evaluations, such as the cost/benefit ratio of technologies, the safe

concentration of chemicals, and even the predicted economic performance

of industries. Their treatment of the affect heuristic fits the present model of

attribute substitution. 

In the same vein, Kahneman and Ritov (1994) and Kahneman, Ritov, and

Schkade (1999) proposed that an automatic affective valuation – the emo-

tional core of an attitude – is the main determinant of many judgments and

behaviors. In the study by Kahneman and Ritov (1994), 37 public causes were

ranked by average responses to questions about (i) the importance of the is-

sues, (ii) the size of the donation that respondents were willing to make, (iii)

political support for interventions, and (iv) the moral satisfaction associated

with a contribution. The rankings were all very similar. In the terms of the

present analysis, the same heuristic attribute (affective valuation) was

mapped onto the distinct scales of a wide range of target attributes. Similarly,

Kahneman, Schkade, and Sunstein (1998) interpreted jurors’ assessments of

punitive awards as a mapping of outrage onto a dollar scale of punishments.

In an article titled “Risk as Feelings”, Loewenstein, Weber, Hsee, and Welch

(2001), offered a closely related analysis in which emotional responses, such

as the intensity of fear, govern diverse judgments (e.g., ratings of the proba-

bility of a disaster). 

In terms of the scope of responses that it governs, the natural assessment of

affect should join representativeness and availability in the list of general-pur-

pose heuristic attributes. The failure to identify the affect heuristic much ear-

lier, as well as its enthusiastic acceptance in recent years, reflect significant

470

---