mindless2.dvi

The Case for Mindless Economics

†

Faruk Gul

and

Wolfgang Pesendorfer

Princeton Univ ersity

November 2005

Abstract

Neuroeconomics proposes radical c hanges in the methods of economics. This essay dis-

cusses the propo sed changes in methodology, together with the the neuroeconomic critique

of standard economics. We do not assess the contributions or promise of neuroeconomic

research. Rather, we oﬀer a response to the neuroeconomic critique of standard economics.

†

This research was supported by grants from the National Science Foundation. We thank Drew

Fudenberg and Philipp Sadowski for helpful comments and suggestions.

1. Introduction

Neuroeconomics proposes radical changes in the m ethods of economics. This essay dis-

cusses the proposed c hanges in methodology, together with the the neuroeconomic critique

of standard economics. Our deﬁnition of neuroeconomics includes research that makes no

speciﬁc reference to neuroscience and is traditionally referred to as psychology and eco-

nomics.Weidentifyneuroeconomicsasresearch that implicitly or explicitly makes either

of the following two claims:

Assertion I: Psychological and physiological evidence (such as descriptions of hedonic

states and brain processes) are directly relevant to economic theories. In particular, they

can be used to support or reject economic models or even economic methodology.

Assertion II: What makes individuals happy (‘true utility’) diﬀers from what they

choose. Economic welfare analysis should use true utility rather than the utilities gov erning

choice (‘choice utility’).

Neuroeconomics goes beyond the common practice of economists to use psychological

insights as inspiration for economic modeling or to take into account experimental evidence

that challenges behavioral assumption s of economic models. Neuroeconomics appeals di-

rectlytotheneuroscienceevidencetorejectstandardeconomicmodelsortoquestion

economic constructs. Camerer, Loewenstein and Prelec (2005) (henceforth CLP (2005))

express the neuroeconomics critique as follows:

“First, we show that neuroscience ﬁndings raise questions about the usefulness of some

of the most common constructs that economists commonly use, such as risk aversion,

time preference, and altruism.” (p. 31-32)

In section 5 of this essay, we argue that Assertion I of the neuroeconomic critique mis-

understands economic methodology and underestimates the ﬂexibility of standard models.

Economics and psychology address diﬀeren t questions, utilize diﬀerent abstractions, and

address diﬀeren t types of empirical evidence. Neuroscience evidence cannot refute eco-

nomicmodelsbecausethelattermakenoassumptions and draw no conclusions about the

physiology of the brain. Conversely, brain science cannot revolutionize economics because

the latter has no vehicle for addressing the concerns of economics. We also argue that the

methods of standard economics are much more ﬂexible than it is assumed in the neuroe-

conomics critique and illustrate this with examples of how standard economics deals with

inconsistent preferences, mistake s, and biases.

Neuroeconomistsimportthequestionsandabstractions of psychology and re-interpret

economic models as if their purpose we re to address those questions. The standard eco-

nomic model of choice is treated as a model of the brain and found to be inadequate. Either

economics is treated as amateur brain science and rejected as such or brain evidence is

treated as economic evidence to reject economic models.

Kahneman (1994) asserts that subjectivestatesandhedonicutilityare“legitimate

topics of study”. This may be true, but such states and utilities are not useful for calibrating

and testing standard economic models. Discussions of hedonic experiences play no role in

standard economic analysis because economics makes no predictions about them and has no

data to test such prediction. Economi sts also lack the means for integrating measurement

of hedonic utility with standard economic data. Therefore, they have found it useful to

conﬁne themselves to the analysis of the latter.

The neuroeconomics program for change in economics ignores the fact that economists,

even when dealing with questions related to those studied in psychology, have diﬀerent

objectiv es and address diﬀerent empirical evidence. These fundamental diﬀerences are

obscured by the tendency of neuroeconomists to describe both disciplines in very broad

terms.

“Because psychology systematically explores human judgement, behavior, well-being

it can teach us important facts about how humans diﬀer from the way traditionally

described by economics,” (Rabin (1998)).

Note the presumption that across disciplines there is a single set of constructs (or facts) for

describing ho w humans are. Rabin omits that economics and psychology study diﬀerent

kinds of beha vior and, more importantly, focus on diﬀerent variables that inﬂuence behav-

ior. Realistic assumptions and useful abstractions when relating visceral cues to behavior

may be less realistic or useful when relating behavior to market variables. Consider the

following two statements:

“Much aversion to risks is driven by immediate fear responses, which are largely trace-

able to a small area of the brain called the amygdala;”(Camerer, Loewenstein and

Prelec (2004), p. 567 (henceforth CLP (2004)).

“A decision-maker is (globally) risk averse, [...] if and only if his von Neumann-

Morgenstern utility is concave at the relevant (all) wealth levels.” Ingersoll (1987).

Which of these statements is (more) true? Which provides a better understanding of

risk aversion? Most researchers recognize the various terms in the second statement as

abstractions belonging to the specialized vocabulary of economics. Though less apparent,

the language of the ﬁrst statement is equally specialized in its use of discipline-speciﬁc

abstractions. The terms ‘immediate fear’ and ‘traceable’ are abstractions of psychology

and neuroscience. Moreov er, the term ‘risk aversion’ represents adiﬀerent abstraction in

the t wo statements above. For Ingersoll, risk aversion is an attitude towards monetary

gambles. For CLP (2004), risk aversion seems to be a much broader term that is readily

applied to decisions involving plane tra vel. It mak es little sense to insist that the economic

notion of risk aversion is false while the psychological notion is true.

We discuss Assertion (II) of the neuroeconomic critique in section 6. We argue that the

assertion misunderstands the role of welfare analysis in economics. Standard economics

identiﬁes we lfare with choice, i.e., a c h ange (in consumption) is deﬁned to be welfare

improving if and only if, given the opportunity, the individual would choose to make that

change. The neuroeconomic critique of standard w elfare analysis mistakes the economic

deﬁnition of welfare for a theory of happiness and proceeds to ﬁnd evidence against that

theory. The standard deﬁnition of we lfare is appropriate because standard economics has

no therapeutic ambition; it does not try to improve the decision-maker but tries to evaluate

how economic institutions mediate (perhaps psychologically unhealthy) behavior of agents.

Standard w elfare economics functions as a part of positive economics. It provides a

benchmark for the performance of economic institutions at aggregating individual prefer-

ences. Economists use welfare analysis to explain the persistence of some (eﬃcient) insti-

tutions or to identify problems and anomalies in models of other (ineﬃcient) institutions.

For example, observing that an existing institution leads to Pareto eﬃcient outcomes may

increase the researcher’s conﬁdence in his model, while noting that the institution leads

to Pareto ineﬃciency ma y lead researchers to seek explanations for the persistence of that

institution. Within this conception of welfare econom i cs, what is relevant are the agents’

interests (or preferences) as perceived by the agents themselves. An institution’s eﬀective-

ness at maximizing the true happiness of its participants cannot justify the persistence of

that institution if the criterion for true happiness conﬂicts with the participants’ revealed

preferences. After all, only the latter plays a role in behavior.

Neuroeconomists expect recent developments in psychology and brain science to yield

answers to age-old philosophical questions such as “what is happiness?”; “should we be

willing to take actions contrary to a person’s wishes if we happen to know that such actions

will make them happier?” andinsistonanewnotionofwelfarebasedontheseanswers.

Perhaps a therapist or a medical professional is guided by his answers to the two ques-

tions above; he ma y fashion his advice to advance the perceived objectives of the patient

or to increase the patient’s true happiness, as deﬁned by the therapist himself.

Neu-

roeconomic welfare analysis assumes a relationship between the economist and economic

agents similar to the therapist-patien t relationship. Normative economics is therefore iden-

tiﬁed with eﬀective therapy. The economist/therapist can inﬂuence individuals’ happiness

by dispensing compelling advice or by inﬂuencing the decisions of powerful (and perhaps

paternalistic) intermediaries. For example, Kahneman (1994) suggests that there is

“...a case in favour of some paternalistic interventions, when it is plausible that

the state knows more about an individual’s future tastes than the individual knows

presently.”

Hence, the goal of welfare economics and perhaps the goal of all economics is to aﬀect

changes that result in greater happiness to all. In this endeavor neuroeconomists plan to

enlist the support of the state — a stand-in for a benign therapist — who may, on occasion,

conceal facts and make decisions on behalf of the individual’s future selve s.

Neuroeconomists seek a welfare criterion that is appropriate f or an economist who is

part social scientist and part advocate/therapist; someone who not only analyzes economic

This description might ov er-state the therapist discretion. Either a professional code or market forces

ma y limit the extent to which he can pursue the patient’s true happiness. Hence, the two philosophical

questions above may or ma y not ha ve some relevance to the therapist. Our contention is that they have

none for economists.

phenomena but also plays a role in shaping them. Neuroeconomists assert that the stan-

dard economic welfare criterion is n ot adequate for this task. Our response to this criticism

is simple: the standard welfare criterion is not in tended to facilitate advocacy for therapeu-

tic interv e ntions. The standard approac h assumes a separation between the economist’s

roleassocialscientistandtherolethatsomeeconomistsmayplayasadvisorsoradvocates.

This separation is valuable because it enables economists to analyze and compare diﬀerent

institutions without having to agree on the answers to diﬃcult philosophical questions.

Besides the t wo assertions stated above, neuroeconomists pose an additional chal-

lenge to standard economics: they argue that economics should tak e advantage of recent

improvements in neuroscience, in particular, improvements in measurements. They claim

that these improvements may facilitate the uniﬁcation of economics and brain science:

“This ‘rational choice’ approach has been enormously successful. But now advances

in genetics and brain imaging (and other techniques) have made it possible to observe

detailed processes in the brain better than ever before. Brain scanning (ongoing at

the new Broad Imaging Center at Caltech) shows which parts of the brain are active

when people make economic decisions. This means that we will eventually be able to

replace the simple mathematical ideas that have been used in economics with more

neurally-detailed descriptions.” Camerer (2005).

We discuss the uniﬁcation argument in section 7. Our main point is that the separation

of economics and brain science is a consequence of specialization around diﬀerent questions

and diﬀerent data; it has little to do with technological limitations in measuring brain

activity. Therefore, there is no reason to expect improvements in such technologies to lead

to a uniﬁcation.

In this essay, we d o not assess the contrib u tions or promise of neuroeconomic researc h.

Instead, we oﬀer a response to the neuroeconomic critique of standard economics. Our

conclusion is that the neuroeconomic critique fails to refute an y particular (standard)

economic model and oﬀers no challenge to standard economic methodology.

Inthenextsection,wedeﬁne the standard approach (or standard economics) and the

neuroeconomics approach. In section 3, we discuss how the diﬀerent goals of psyc hology

and of economics necessitate diﬀerent abstractions. As an example, we contrast the eco-

nomic concepts of “complements” and “externalities” with the psychological concept of a

“cue.” In section 4, we presen t an example of eac h approach to illustrate our classiﬁca-

tion and highlight the diﬀerences in the concerns and abstractions of standard economics

and neuroeconomics. In sections 5, 6, and 7 we discuss the three main arguments of the

neuroeconomics critique. Section 8 conta ins our closing remarks.

2. The Two Approac hes: Deﬁnitions and Objectives

2.1 Standard Economics

The standard approach to behavioral economics extends standard choice theoretic

methods to analyze variables that are often ignored. Some of these extensions are modest

and entail little more than specifying a richer set of preferences over the same economic

consequences. Others necessitate novel descriptions of the relevant economic outcomes.

Yet, in most cases, the subsequent analysis is very similar to what can be found in a

standard graduate textbook.

In the standard approach, the term utility maximization and choice are synonymous.

A utility function is always an ordinal index that describes ho w the individual ranks

various outcomes and how he behaves (chooses) given his constraints (a vailable options).

The relevant data are revealed preference data; that is, consumption choices give n the

individual’s constraints. These data are used to calibrate the model (i.e., to identify

the particular parameters) and the resulting calibrated models are used to predict future

choices and perhaps equilibrium variables such as prices. Hence, standard (positive) theory

identiﬁes choice parameters from past behavior and relates these parameters to future

behavior and equilibrium variables.

Standard economics focuses on revealed preference because economic data come in

thisform. Economicdatacan—atbest—revealwhattheagentwants(orhaschosen)

in a particular situation. Suc h data do not enable the economist to distinguish between

what the agent intended to choose and what he ended up choosing; what he chose and

what he ought to ha ve chosen. The standard approach provides no methods for utilizing

non-choice data to calibrate preference parameters. The individual’s coeﬃcient of risk

aversion, for example, cannot be identiﬁed through a physiological examination; it can

only be rev ealed through choice behavior. If an economist proposes a new theory based on

non-choice evidence then either the new theory leads to novel behavioral predictions, in

which case it can be tested with revealed preference evidence, or it does not, in which case

the modiﬁcation is vacuous. In standard economics, the testable implications of a theory

are its content; once they are identiﬁed, the non-c h oice evidence that motivated a novel

theory becomes irrelevant.

As its welfare criterion, standard economics uses the individuals’ choice beha vior, that

is, revealed preferences. Alternative x is deemed to be better than alternative y if and only

if, given the opportunity, the individual would c hoose x over y.

Hence, welfare is deﬁned

to be synonymous with choice behavior.

In standard economics, an individual’s decisions may improve when a constraint is

relaxed. For example, an agent may make better decisions if he is given better information,

more resources, or more time to make his decision. How ever, standard economics has no

therapeutic am bition, i.e., it does not try to evaluate or improve the individual’s objectives.

Economics cannot distinguish between choices that maximize happiness, choices that reﬂect

a sense of duty, or choices that are the response to some impulse. Moreo ver, standard

economics takes no position on the question of which of those objectives the agent should

pursue.

The purpose of economics is to analyze institutions, such as trading mechanisms and

organization structures, and to ask how those institutions mediate the int erests of dif-

ferenteconomicagents. Thisanalysisisuseful irrespective of the causes of individuals’

preferences. Standard economics ignores the therapeutic potential of economic policies

and leaves it to therapists, medical professionals, and ﬁnancial advisors to help individuals

reﬁne their g oals.

2.2 Neuroeconomics

“‘This new approach, which I consider a revolution, should provide a theory of how

people decide in economic and strategic situations,’ said Dr. Aldo R ustichini, an

The welfa re statement is made relative to the constraints the agent faces. For example, the agent

ma y be imperfectly informed of the consequences of his actions. In that case, the choice of x is welfare

maximizing given the agent’s information. If the agent had better information, he might choose y and

hence y is the welfare maximizing choice for a better informed agent. See our discussion of mistake s in

Section 5.1.

economics professor at the University of Minnesota. ‘So far, the decision process has

been for economists a black box.’”

Later, in the same article, the author explains that

“In a study published in the current issue of the journal Science, Dr. Cohen and his

colleagues,includingDr.AlanG.SanfeyofPrinceton,tookimagesofpeople’sbrains

as they played the ultimatum game, a test of fairness between two people. In the

ultimatum game, the ﬁrst player is given, say, £10 in cash. He must then decide how

muchtogivetoasecondplayer. Itcouldbe£5,thefairestoﬀer, or a lesser amount

depending on what he thinks he can get away with. If Player 2 accepts the oﬀer, the

money is shared accordingly. But if he rejects it, both players go away empty-handed.

It is a one-shot game, a nd the players never meet again. Most people in the shoes of

Player 2 refuse to take amounts under £2 or £3, Dr. Cohen said. They would rather

punish the ﬁrst player than feel cheated. ‘But this makes no economic sense,’ he said.

‘You’re better oﬀ with something than nothing.’”

As the quotes abo ve illustrate, neuroeconomics emphasizes the physiological and psycho-

logical processes underlying decision-making. Theobjectiveistorelatethedecision-making

process to physiological processes in the brain or to descriptions of emotional experiences.

From its predecessor, psychology and economics,

neuroeconomics inherits the idea of

modeling the decision-maker as a collection of biases and heuristics susceptible to system-

atic errors (eﬀects) and inconsistencies (reversals). Hedonic utilities (true utilities) are

primitives, deﬁned independen tly of behavior, while behavior is determined by biases and

heuristics. The focus is on showing how factors that have no eﬀect on these true utilities—or

at least aﬀect these utilities in a manner that is ignored by standard economics—inﬂuence

behavior.

Neuroeconomics is therapeutic in its ambitions: it tries to improve an individual’s

objectives. The central questions of neuroeconomists are: How do individuals make their

c hoices? How eﬀective are they at making the choices that increase their own wellbeing?

By con trast, economists analyze how the choices of diﬀerent ind ividuals interact within a

particular institutionalsetting,giventheirdiﬀering objectives.

“Brain Experts Now Follo w the Money,” by Sandra Blak eslee, New York Times, June 17, 2003.

This line of inquiry is often referred to as behavioral economics. We have avoided using this term,

in order to distinguish it from standard economics models that deal with similar behavioral issues.

3. Diﬀerent Objectives Demand Diﬀerent Abstractions

Neuroeconomistsarguethatthetimeisripeforthemethodologyofeconomicsto

be brought in line with the methods and ideas of psychology and neuroscience. The

neuroeconomic critique begins with the implicit or explicit assumption that economics,

psychology and possibly other social sciences all address the same set of questions and

diﬀer only with respect to the answers they provide:

“More ambitiously, students are often bewildered that the models of human nature of-

fered in diﬀerent social sciences are so diﬀerent, and often contradictory. Economists

emphasize rationality; psychologists emphasize cognitive limits and sensitivity of choi-

ces to contexts; anthropologists emphasize acculturation; and sociologists emphasize

norms and social constraint. An identical question on a ﬁnal exam in each of the

ﬁelds about trust, for example, would have diﬀerent “correct” answers in each of the

ﬁelds. It is possible that a biological basis for behavior in neuroscience, perhaps com-

bined with all-purpose tools like learning models or game theory, could provide some

uniﬁcation across the social sciences (cf. Gintis, 2003).” CLP (2004) p. 572-3.

Contrary to the view expressed in the quoted paragraph, economics and psychology do

not oﬀer competing, all-purpose models of h uman nature. Nor do they oﬀer all-purpose

tools. Rather, each discipline uses specialized abstractions that have proven useful for

that discipline. Not only is the word trust muc h less likely to come up in an economics

exam than in a psychology exam, but when it does appear in an economics exam, it means

something diﬀerent and is associated with a diﬀerent question, not just a diﬀerent answer.

Far from being an all-purpose tool, game theory is a formalism for stripping away all

strategically irrelevant details of the context, details that Gintis describes as central for

psychologists. Similarly, a learning model in economics is diﬀerent than a learning model in

psychology. For an economist, a theory o f learning m ight be a process of Bayesian inference

in a multi-armed bandit model. This theory of learning is useful for addressing economic

phenomena such as patent races but may be inappropriate for cognitive psychologists.

Once the goals of economics and psyc hology are stated in a manner that makes it

seem as if the two disciplines address the same questions and deal with the same empirical

evidence, it becomes reasonable for neuroeconomists to inquire which discipline has the

better answers and the better tools for providing answers.

CLP assert that

“neuroscience ﬁndings raise questions about the usefulness of some of the most com-

mon constructs economists commonly use, such as risk aversion, time preference, and

altruism,”

Risk a version and time preference are indispensable concepts for modern economics. The

authors really intend to question the validity of these concepts; in essence, they are assert-

ing that there is no such thing as risk aversion or time preference. ‘Time preference’ and

‘risk ave rsion’ are useful economic abstractions just as ‘cue-conditioned cognitive process’

or ‘hedonic forecasting mec hanisms’ are abstractions useful in neuroscience and psychol-

ogy. The truth (or falsehood) of an abstraction cannot be evaluated independently; the

only wa y to assess these abstractions by assessing — within each discipline — the theories

that use them.

Consider the reverse procedure of using evidence from economics in brain science.

Suppose that we ﬁnd that drug addicts generally satisfy the strong axiom of revealed

preference in their demand behavior. Can w e argue that since addicts maximize some

utility function, there are no separate brain functions and conclude then that the “limbic

system” does not exist? This line of reasoning is, of course, absurd because brain science

takes no position on whether c hoices satisfy the strong axiom of revealed preference or not.

Theargumentthatevidencefrombrainsciencecanfalsifyeconomictheoriesisequally

absurd. Hsu and Camerer write,

“For neuroeconomists, knowing more about functional specialization, and how regions

collaborate in diﬀerent tasks, could substitute familiar distinctions between categories

of economic behavior (sometimes established arbitrarily by suggestions which become

modeling conventions) with new ones grounded in neural detail. For example, the

insula activity noted by Sanfey et al. in bargaining is also present when subjects

choose between gambles with ambiguous odds of winning, relative to ‘risky’ gambles

with known odds (Ming Hsu and Camerer, 2004).”

Economists who are not interested in the physiological mechanism behind economic de-

cisions will not ﬁnd the level of insula activity useful for classifying behavior. What Hsu

and Camerer consider “distinctions based on arbitrary modeling conv entions” are likely to

be much more useful to economists, given their own objectives and given the type of data

that is available to them.

The presumption that economics and psyc hology have the same goals and rely on the

same data facilitates three types of critiques of standard economics:

1. Failure of Rationality: Economic models of choice fail to tak e account of psychological

or physiological phenomena or evidence.

2. Inadequacy of Rationality: Rationality — deﬁned to mean some sort of consistency in

the behavior and preferences of individuals — is not an adequate starting point for

economics because consistency of behaviors does not mean that these behaviors will

lead to good outcomes.

3. Uniﬁcation: Recent advances in neuroscience provide ric h new sources of data. Eco-

nomics must take advantage of these developments.

We address these arguments in sections 5, 6, and 7 respectively. We illustrate in

the remainder of this section how the diﬀerent goals psychology and economics and the

diﬀerent data a vailable to these two disciplines necessitate diﬀerent abstractions.

3.1 A Cue or a Complement?

The concept of a “cue” oﬀers a good illustration of how abstractions from psychology

are inappropriate for economics and, conversely, how the corresponding economic con-

cepts are inappropriate for psychology and neuroscience. Psyc hologists call a stimulus

that triggers a desire or a cra v ing for a particular consumption or activit y a “cue” or a

“cue-elicited craving.”

For example, eating a hamburger may be a cue that triggers a

craving for French fries. Drinking coﬀee may trigger a craving for cigarettes. Visiting the

location of previous drug consumption may trigger a craving for drugs. As the example of

drug consumption illustrates, cues ma y be determined endogenously through a process of

conditioning.

Psychologists ﬁnd the concept of a cue useful because they think of cues as

See Laibson (2001) for an economic model that describes psychological cues.

The agen t frequently consumed the drug at a particular location and - as a result of this consumption

history - being in that location triggers a cra v ing for drugs. Similarly, the agent frequently smoked a

cigarette while drinking coﬀee in the past. This - perhaps incidental - pairing of consumption goods in the

past implies tha t coﬀee consumption triggers a craving for cigarettes.

exogenous variables in experimental settings. They investigate the physiological mecha-

nisms behind the development of and the reaction to cues. For economists, the notion of a

cueisnotusefulbecauseitlumpstogether two distinct economic phenomena: complements

and externalities.

Hamburgers and fries are complementarygoodsjustlikeforksandknives. Forksdonot

generate a craving for knives and therefore psy chologists w ould not consider the fork/knife

complement arity to be the same phenomenon as the hamburger/fries complemen tarity. For

economists the physiological distinction between the two examples is unimportant. What

matters is that demand for those goods responds in a similar way to price changes.

Another form of complementarities is the one associated with non-separable prefer-

ences over consumption streams. For example, consider an individual who enjoys building

matchstick models and, as a result of this hobb y, dev elops a complementary demand for

matches and glue. The complementary demand for matches and glue is acquired through

learning a hobby while the complemen tary demand for coﬀee and cigarettes is acquired

through a process of conditioning. For a psychologist, who is in terested in the underlying

causes of preferences, the coﬀee/cigarette and glu e/matc hsticks complementarities repre-

sent distinct phenomena. The ﬁrst is an example of conditioning while the second is an

example of learning. However, both examples are similar in terms of the variables that

economists observe and care about (prices, demand).

In the cue-response pairs above, the individual controls both the cue and the response.

Ho wever, some cues are not under the con trol of the individual. For example, a former drug

addict may experience a craving for drugs as he observes d rug dealers in his neighborhood.

In econom ics, this eﬀect is captured by the notion of an externality. For economists, the

neighborhood eﬀectondrugaddictsissimilartotheeﬀect of an improved network of roads

on car buyers. Both are examples of an externality that causes a shift in the demand for a

good. For psychologists, the craving for drugs b y seeing drug-dealers in the neighborhood

is similar to the craving for cigarettes caused by drinking coﬀee. On the other hand, they

would consider it absurd to describe the car buying example and drug addiction example

as being the same phenomenon because the underlying psychological mechanisms are very

diﬀerent. It would be equally absurd to insist that economists treat the neighborhood

eﬀect on drug d emand as the same phenomenon as the cigarette/coﬀee complementarity.

In economics, there are important reasons for distinguishing between complemen tarities

and externalities. For example, externalities often suggest market failures while comple-

mentarities do not.

Economists and psychologists use diﬀerent abstractions because they are interested in

diﬀerent phenomena and must confront diﬀerent data. ‘Cue-triggered responses’ is not a

useful abstraction in economics because it lumps togeth er distinct economic phenomena.

Conversely, the economic abstraction of a complement is not useful in psyc hology because

it lumps together phenomena with diﬀerent psychological mechanisms.

4. The Two Approaches: Examples

In this section, w e illustrate the standard approach to nove l behavioral phenomena

with a discussion of the paper “Temporal Resolution of Uncertainty and Dynamic Choice

Theory,” by Kreps and Porteus (1978). We illustrate the neuroeconomics approach w ith

a recent paper by K¨oszegi and Rabin (2005) entitled “Reference-Dependen t Utility.”

4.1 The Standard Approach: Resolution of Uncertainty

An individual goes to the hospital on Friday to have a biopsy of a suspicious mass. In

case the biopsy detects cancer, surgery will be scheduled for the following Monday. When

given a choice between waiting a few hours to learn the result or going home and learning

the result on Monday, the individual chooses to wait. The decision to incur the cost of

waiting seems plausible but is inconsistent with standard theory. Standard expected utility

maximizers are indiﬀerent to the timing of resolution of uncertainty.

In “Temporal Resolution of Uncertainty and Dynamic Choice” Kreps and Porteus

(1978) (henceforth Kreps-Porteus) expand the standard model of decision making under

uncertaint y to include anxious individuals such as the patien t in the example above.

Suppose there are two dates t =1, 2andaﬁnite set of prizes Z that will be consumed at

date 2 (“surgery” or “no surgery” in the example above). Standard decision theory under

uncertaint y deﬁnes lotteries over Z as the choice objects. But this description does not

The relationship bet ween anxiety and preference for early or late resolution of uncertainty is explored

and further developed in the work of Caplin and Leahy (2001).

diﬀerentiate between lotteries that resolve at date 1 and lotteries that resolve at date 2 -

and therefore cannot capture the anxious patient described above.

Let D

be the lotteries o ver Z and let D

be lotteries over D

.Hence,D

is the

set of lotteries over lotteries over Z. We refer to elemen ts of D

as date-1 lotteries and

elements of D

as date-2 lotteries. We can describe the problem of the anxious patient

asachoicebetweentwolotteriesinD

. Suppose the p robability of surgery is α.Waiting

for the results until Monday corresponds to a date-1 lottery where, with probability 1,

the individual will face the date 2 lottery that yields surgery with probability α and no

surgery with probability 1 − α. Learning the result on Friday corresponds to the date-1

lottery where, with probability α, the individual faces a date-2 lottery that yields surgery

with probability 1 and, with probability 1 − α, the individual faces a date-2 lottery that

yields surgery with probability 0.

Let p, q denote elements in D

and µ, ν denote elements in D

.Forsimplicity,we

only consider lotteries with ﬁnite supports. Let µ(p)betheprobabilitythatµ chooses the

lottery p ∈ D

. Standard expected utility theory identiﬁes µ with the implied probability

distribution over prizes, i.e., the probability distribution q ∈ D

that assigns probability

q(z)=

µ(p)p(z)(∗)

to prize z ∈ Z. Therefore, standard expected utility theory cannot accommodate the

cancer patient’s strict preference for learning the test results on Friday.

The Kreps-Porteus model takes as a primitive an individual’s preferences º (choices)

over the date-1 lotteries, D

. Some date-1 lotteries yield a particular date-2 lottery with

probability 1. We call such lotteries degenerate date-1 lotteries. In the example above,

learning the test results on Monday corresponds to such a lottery. Restricting the pref-

erence º to degenerate date-1 lotteries, induces a preference on D

, the date-2 lotteries.

Let δ

denote the date-1 lottery that yields the date-2 lottery p with probability 1. The

induced preference º

(on D

)isdeﬁned as follo ws:

p º

q if and only if δ

º δ

Kreps-Porteus assume that º and º

satisfy the standard von Neumann-Morgenstern

axioms: hence, the preferences are complete, transitive, satisfy the independence axiom,

and satisfy an appropriate continuity assumption. Kreps-Porteus sho w that the preferences

on D

satisfy those assumptions if and only if there are utility functions u and W such

that µ º ν if and only if

z∈Z

u(z)p(z)

µ(p) ≥

z∈Z

u(z)p(z)

ν(p)

The formula above applies the standard expected utility formula twice. The term in

brackets is the expected utility formula for lotteries that resolve at date 2 whereas the

outer term is the expected utility form u la for lotteries that resolve at date 1.

The Kreps-P orteus formalism yields a precise deﬁnition of a new phenomenon: pref-

erence for early (or late) resolution of uncertainty.Letµ, ν be two elements of D

that

imply the same distribution over prizes. The lottery µ resolves all uncertainty at date 1

while the lottery ν resolves all uncertainty at date 2. In the example above, µ corresponds

to the situation where the patient learns the test result on Friday and ν corresponds to the

situation where the patient learns the test result on Monday. The individual has a prefer-

ence for early resolution of uncertainty if he prefers µ over ν. Kreps-Porteus show that a

preference for early resolution of uncertainty implies (and is implied by) the convexity of

W .

Note the key steps in the modeling exercise: Kreps-Porteus start with a nov el psy-

c hological phenomenon and identify the economically relevant consequences of that phe-

nomenon. Once the economically meaningful consequences are iden tiﬁed, the psychological

causes become irrelevan t. For the patient above, the source of the preference for early res-

olution of uncertainty is anxiety. But there could be many other reasons for a preference

for early resolution of uncertainty. Suppose, for exa m ple, the agent owns a lottery ticket

that will either yield a large reward (with small probability) or nothing. Prior to the

lottery dra wing, the agent must decide which car to purchase. The outcome of the lot-

tery will t ypically a ﬀect the optimal car buying decision and, therefore, the agent would

be better oﬀ if the lottery drawing was held earlier. Hence, the induced preferen ces over

lotteries imply a preference for early resolution of uncertainty. In t his case, the agent has

perfectly standard preferences. The preference for early resolution of uncertainty comes

about because the agent has a second pa yoﬀ-relevant decision to make after choosing a

lottery.

In the two examples, the causes of the decision-maker’s preference for early resolution

of uncertainty are diﬀerent. In the ﬁrst example the patient is trying to avoid anxiety

while in the second decision problem he is trying to make a better informed decision.

For a standard economist this distinction is irrelevant because standard economics does

not study the causes of preferences. For standard theory, the only relevant distinctions

between the two examples are the ones that can be identiﬁed through the decision-makers’

preferences.

The Kreps-Porteus theorem identiﬁes a formu la that resembles standard expected

utility applied separately at each decision date. While the formula is suggestive of a mental

process, this suggestiveness is an expositional device not meant to be taken literally.

The

formula encapsulates the behavioral assumptions of the theory in a user-friendly w ay and

thereby facilitates applications of the theory to (more complicated) economic problems.

The theory is successful if preference for early resolution of uncertain ty turns out

to be an empirically important phenomenon; that is, if models that incorporate it are

successful at addressing economic behavior. The role of the axioms is to summarize the

empirical c ontent of the theor y independently of the speciﬁc application. The generality of

the represen tation theorem, the usefulness of the key parameters, the ease with which the

parameters can be measured and, most importan tly, the empirical success of the model at

dealing with economic evidence determine theextenttowhichthetheorysucceeds.

Kreps-Porteus’s model has been generalized and applied to Macroeconomics and Fi-

nance (see Epstein and Zin (1991a, 1991b)). These ﬁelds analyze dynamic consumption

choice under uncertainty. The primitives of Kreps-Porteus’s model (dated lotteries) are

For example, the Kreps-P orteus independence axiom may not be appropriate in the case where the

agent has a second decision to make whereas the anxious patient might very well satisfy it.

A teacher in an intermediate micro class migh t sa y something like, “the consumer equates the marginal

utility of consuming the good to the marginal utility of the last dollar spent on the good,” while explaining

a ﬁrst order condition in a partial equilibrium model with separable preferences. This statement is meant to

pro v ide some intuition for the ﬁrst order condition, not as a description of the consumer’s mental process:

the marginal utilities in question depend on the particular utility function used to represent the preference

and hence are, to some extent, arbitrary. There is no presumption that either these particular marginal

utilities or the underlying calculus arguments are the actual currency of the consumer’s reasoning.

easily adapted to match closely the objects studied in Macroeconomics and Finance. The

fact that Kreps-P orteus strip all economically irrelevant details from their model is essen tial

for the success of this adaptation.

4.2 Neuroeconomics: Reference Dependent Utility

In a well-known experiment (Thaler 1980)), a random subset of the subjects are

assigned one unit of some object and then all subjects’ reservation prices for this object

are elicited. The price at which subjects who were assigned a unit are willing to sell it

typically exceeds the price at which the remaining subjects are willing to buy a unit. This

phenomenon is referred to as the endowment eﬀect and has m otivated models that add a

reference point to the utility function.

K¨oszegi and Rabin (2005) (henceforth K¨oszegi-Rabin) propose a novel reference-

dependent preference theory. To understand the K¨oszegi-Rabin theory, consider a ﬁnite

setofchoiceobjectsX.

A reference-dependent utility function U, associates a utility

with each reference point z ∈ X and each choice object x ∈ X.Hence,U : X × X → IR,

where U(x, z) is the utilit y of x give n the reference z. This formulation of utility is not

new;thenoveltyisintheadoptionofK¨oszegi (2004)’s notion of a personal equilibrium to

determine the reference point. In this setting, a personal equilibrium for an decision-maker

facing the choice set A is any x ∈ A such that

U(x, x) ≥ U(y, x)(2)

for all y ∈ A.Hence,K¨oszegi-Rabin deﬁne the reference point as the x that ultimately

gets chosen. It follows that an alternative x ∈ A is optimal (i.e., a possible choice) for

aK¨oszegi-Rabin decision-maker if (and only if) condition (2) abov e is satisﬁed. K¨oszegi-

Rabin assume that U has the form

U(x, y)=

k∈K

(x)+

k∈K

µ(u

(x) − u

(y)) (3)

where µ is an increasing function with µ(0) = 0 and K is some ﬁnite set indexing the

relevant hedonic dimensions of consumption. K¨oszegi-Rabin note that these consumption

dimensions “should be speciﬁed based on psychological principles.”

An element x ∈ X may be uncertain (i.e., may be a lottery).

K¨oszegi-Rabin also require that

U(x, y) ≥ U(y, y)impliesU(x, x) >U(y, x)(4)

for all x, y ∈ X.

There are certain striking diﬀerences between the approaches of Kreps-Porteus and

K¨oszegi-Rabin. In Kreps-Porteus, the formula is an “as if” statement and the assumed

restrictions on choice behavior (axioms) are the content of the theory. In contrast, K¨oszegi-

Rabin interpret the procedure associated with computing a personal equilibrium (i.e.,

ﬁnding x that satisfy equation (2)) as a description of the underlying psycho lo gical process.

K¨oszegi-Rabin focus on psychologica l evidence supporting this procedure and th e various

assumptions on the function U.

To facilitate the comparison of the diﬀerence in the t wo approac hes, we provide a

revealed preference analysis o f the K¨oszegi-Rabin model for the case of no uncertainty.

Let X be ﬁnite and let Y be the set of all nonempty subsets of X. A function c : Y → Y is a

choice function if c(A) ⊂ A for all A ∈ Y . In revealed preference terms, the K¨oszegi-Rabin

model is an investigation of a special class of choice functions. Given any state dependent

utility function U,deﬁne C(·,U)asfollows:

C(A, U)={x ∈ A | U(x, x) ≥ U(y,x)∀y ∈ A}

A choice function c is ageneralK¨oszegi-Rabin choice function if there exists a reference

dependent utility function U suc h that c = C(·,U). If the U also satisﬁes (3) and (4)

then c is a aspecialK¨oszegi-Rabin choice function. For any binary relation º,deﬁne the

function C

as follows:

(A)={x ∈ A | x º z∀z ∈ A}

It is easy to construct examples where C

(A)=∅ unless certain assumptions are made on

º. Wesaythatthechoicefunctionc is induced by the binary relation º,ifc(A)=C

(A)

for all A ∈ Y .Itiswell-knownthatC

is a choice function whenever º is complete (x º y

K¨oszegi-Rabin emphasize applications to decision making under uncertain ty. Since we limit our

analysis to a setting without uncertainty, our revealed preference “version” only captures the K¨oszegi-

Rabin model for a limited set o f applications.

or y º x for all x, y ∈ X)andtransitive(x º y and y º z implies x º z for all x, y, z ∈ X).

Ho wever, transitivit y is not necessary for C

to be a choice function. The proposition

characterizes K¨oszegi-Rabin choice functions:

Proposition: Thefollowingthreeconditionsareequivalent:

(i) c is a general K¨oszegi-Rabin choice function

(ii) c is a choice function induced by some complete binary relation

(iii) c is a special K¨oszegi-Rabin choice function

Proof: See Appendix

Note that c = C

is a choice function implies º is complete. Hence, we may omit the

word complete in the above proposition. The equivalence of (i) and (ii) establishes that

abandoning transitivity is the only revealed preference implication of the K¨oszegi-Rabin

theory. The equivalence of (ii) and (iii) implies that the particular functional form (3) and

condition (4) are without loss of generalit y.

The revealed preference analysis answers the following question: suppose the modeler

could not determine the individual ingredients that go into the representation, how can

he check whether or not the decision-maker behaves in a manner consistent with such a

representation? Or to put it diﬀeren tly, how is the behavior of a K¨oszegi-Rabin-decision

maker diﬀeren t from a standard decision-maker? For the case of deterministic choice, the

answer is that the K¨oszegi-Rabin decision-mak er may fail transitivit y.

In con trast, K¨oszegi-Rabin treat the relevant dimension of hedonic utility and the

values of the various options along these dimensions as observable and quantiﬁab le. They

emphasize that this quantiﬁcation requires craft and an understanding of psychological

principles.

“Several aspects of our theory, however, render it short of fully general and formu-

laically applicable. Many of our speciﬁc assumptions are based on intuition rather

than direct evidence.” (p. 31).

The assumptions of many theoretical models are based on intuition rather than direct

evidence. But in standard models, any future test of the assumptions and the underlying

intuitions requires direct (revealed-preference) evidence. Where K¨oszegi-Rabin diﬀer from

standard economics is that psychological principles and (non-cho ice) evidence is viewed as

an alternative form of evidence and it is this type of evidence that is the focus of their

attention.

In K¨oszegi-Rabin, utility indices (u

’s) and attachment disutilities (measured by µ)are

hedonic utilities and are distinct from choice utilities. The K ¨oszegi-Rabin representation is

not only a theory of choice but also a description of the underlying psychological process:

“By all intuition and evidence, the feeling of loss when giving up a mug is a real

hedonic experience, and making choices reﬂecting that real hedonic experience is partly

rational. But as interpreted by Kahneman (2001) and Loewenstein, O’Donoghue, and

Rabin (2003), people seem to over-attend to this experience because they ignore that

the sensation of loss will pass very quickly — behaving as if they would spend much

time longing for the mug they once had.”

Hence, measured feelings are inputs in the K¨oszegi-Rabin analysis. The authors believe

that these m easuremen ts will enable the analyst to identify hedonic utilities that capture

the intrinsic satisfaction of consuming the good (i.e., the u

’s) and hedonic utilities that

capture the real loss associated with giving up the good. Moreov er, they expect hedonic

measurements to distinguish behavior that results from rational assessment of utilities from

behavior that results from over-attending to utilities.

K¨oszegi-Rabin plan to calibrate the model using psychological insights and evidence.

They view the Kreps-P orteus-type insistence on calibrating through revealed preferences as

an un necessary demand for “formulaic applicability.” The model’s success is judged by the

extent to wh ich t he psycho logical process suggested by their formula matches psychological

evidence.

“In K¨oszegi and Rabin (2004), the previous version of this paper, we argue at length (as we do

brieﬂy in the conclusion of this paper) that the consumption dimensions used in our framework should be

speciﬁed based on psych ological principles, and not necessarily correspond directly to quantities of diﬀerent

products.”

5. The Failure of Rationalit y

Neuroeconomists share with man y other critics of economics the view that individual

rationality is an empirically invalid assumption. Over the y ears, critics of rationality ha ve

identiﬁed various economic assumptions as ‘rationality.’ The independence axiom, prob-

abilistic sophistication, monotonicity of payoﬀs in the agent’s own consumption, or the

independence of payoﬀs from the consumption of others hav e all been viewed as implica-

tions of rationality before the emergence of economic models that relax these assumptions.

More recent criticisms of rationality focus on the fact that individuals make systematic

mistakes even in situations where the right choice is clear. The most ambitious critics

of rationality argue that the idea of utility maximization is ﬂawed because individuals

do not maximize an y preference relation. In section 5.2 we argue that these criticisms

typically underestimate the ﬂexibilit y revealed preference methodology. In particular, we

illustrate how standard economics deals with ‘mistakes.’ In section 5.1, we focus on the

evidence reported by neuroeconomists in support of their criticism. We observe that much

of this evidence misses its target because economic models make no predictions about

physiological processes that underly decision making.

5.1 The Neuroeconomic Case Against Preference Maximization:

CLP (2004) oﬀer a short-list of neuroeconomic evidence against the “standard eco-

nomic concept of preference.” The list begins with the following item:

“Feelings of pleasure and pain originate in homeostatic mechanisms that detect depar-

tures from a “set-point” or ideal level, and attempt to restore equilibrium. In some

cases, these attempts do not require additional voluntary actions, e.g., when monitors

for body temperature trigger sweating to cool you oﬀ and shivering to warm you up. In

other cases, the homeostatic processes operate by changing momentary preferences, a

process called “alliesthesia” (Cabanac, 1979). When the core body temperature falls be-

low the 98.6F set-point, almost anything that raises body temperature (such as placing

one’s hand in warm water) feels good, and the opposite is true when body temperature

is too high. Similarly, monitors for blood sugar levels, intestinal distention and many

other variables trigger hunger. Homeostasis means preferences are “state-dependent”

in a special way: The states are internal to the body and both aﬀect preferences and

act as information signals which provoke equilibration....” (CLP (2004), p. 562)

No observation in the above cited paragraph contradicts any principle of preference maxi-

mization. Economic models make no predictions or assumptions about body temperature,

blood sugar levels, or other physiological data and therefore such data cannot refute eco-

nomic models. Sta ndard economics is not committed to a particular theory of what makes

peoplefeelgood. Nordoesitassumethatfeelinggoodiswhatpeoplecareabout.

The second item challenges the adequacy of rev ealed preference data:

“Inferring preferences from a choice does not tell us everything we need to know, and

may tell us very little. Consider the hypothetical case of two people, Al and Naucia,

who both refuse to buy peanuts at a reasonable price (cf. Romer, 2000). The refusal to

buy reveals a common disutility for peanuts. But Al turned down the peanuts because

he is allergic: consuming peanuts causes a prickly rash, shortens his breath, and could

even be fatal. Naucia turned down the peanuts because she ate a huge bag of peanuts at

a circus years ago, and subsequently got sick from eating too much candy at the same

time. Since then, her gustatory system associates peanuts with illness and she refuses

them at reasonable prices. While Al and Naucia both revealed an identical disutility,

a neurally-detailed account tells us more. Al has an inelastic demand for peanuts-you

can’t pay him enough to eat them!-while Naucia would try a ﬁstful for the right price.

..... (CLP (2004), p. 563)

It is often impossible to infer preferences from a single decision. In fact, ﬁnding a small

class of such experiments to identify the individual’s utility function is the central concern

of reve aled preference theory. Hence, not buying pean uts at a single price does not imply

“...Al and Naucia both revealed an identical disutility” and while “a neurally-detailed ac-

count” could “tell us more,” the economically meaningful information can only be elicited

with a change in prices. In standard economics, the reasons for a particular ranking of

alternatives is irrelevant. That Al might die from consuming peanuts and Naucia simply

doesn’t like consuming them matters only if at some price Naucia is willing to do so and Al

is not; and even then, it is the latter fact and not the underlying reasons that are relevan t.

We delay the discussion of the third item to the next section where we discuss w elfare

analysis. The fourth item discusses what standard economics would consider a form of

money illusion: decision-mak ers may deriv e “direct” utility from money, beyond the utility

they derive from the g oods purchased with money.

“A fourth problem with preference is that people are assumed to value money for what

it can purchase — that is, the utility of income is indirect, and should be derived from

direct utilities for goods that will be purchased with money. But roughly speaking, it

appears that similar brain circuitry — dopaminergic neurons in the midbrain — is active

for a wide variety of rewarding experiences — drugs, food, attractive faces (cite), humor

(cite) — and money rewards. This means money may be directly rewarding, and it’s

loss painful....” (CLP (2004), p. 565.)

There are straightforward economic tests for identifying money illusion. Such a test would

entail changing prices and nominal wages in a manner that leaves the set of feasible con-

sumption, labor supply pairs unchanged. Then, we could check if this change has shifted

the labor supply curv e. But the issue cannot be addressed by investigating the brain cir-

cuitry and the midbrain, since economic modelsaresilentonthebrainactivityassociated

with decision making.

The ﬁnal item deals with addiction:

“Addiction is an important topic for economics because it seems to resist rational

explanation. .... It is relevant to rational models of addiction that every substance to

which humans may become biologically addicted is also potentially addictive for rats.

Addictive substances appear therefore to be “hijacking” primitive reward circuitry in

the “old” part of the human brain. Although this fact does not disprove the rational

model (since the recently-evolved cortex may override rat-brain circuitry), it does show

that rational intertemporal planning is not necessary to create the addictive phenomena

of tolerance, craving, and withdrawal. It also highlights the need for economic models

of the primitive reward circuitry, which would apply equally to man and rat. .....”

(CLP (2004) p. 565-566).

That substances addictive for rats are also addictive in humans is not relevan t for economics

because (standard) economics does not study rats.

It also does not study the causes of

Presumably, psychologists interested in hu man physiology ﬁnd it worthwhile to study rats because

of the similarities in the neurological make-up of the two species. Apparently, the similarities between the

economic institutio ns of the t wo species are not suﬃcient to generate interests in rats among economists.

preferences. To say that a decision-maker prefers x to y is to say that he never chooses

y when x is also available, nothing more. Hence, addiction can be identiﬁed as a distinct

economic phenomenon only through its distinct choice implications not through the under-

lying brain processes. The fact that addictive substances appear to be “hijacking primitive

reward circuitry,” fails to disprove the rational model not because the cortex may override

rat-brain circuitry but because the rational model addresses neither the brain-circuitry nor

the cortex.

What the authors describe as evidence is in fact a statement of a their philosophical

position. They have decided that the cortex represen t s planned action (rational choice),

while certain processes in other parts (presumably in the midbrain) represent overwhelming

physiological inﬂuences (i.e., the hijac king of the primitive reward circuitry).

“Many of the processes that occur in these systems are aﬀective rather than cognitive;

they are directly concerned with motivation. This might not matter for economics were

it not for the principles that guide the aﬀective system — the way that it operates — is

so much at variance with the standard economics account of behavior.” (CLP (2005)

p. 25-26).

Hence, every decision that is associated with the latter types of processes is interpreted

as evidence that rational choice theory is wrong. This critique fails because standard

economics tak es no position on whether a particular decision represents a manifestation

of free will or a succum bing to biological necessity. Rationality in economics is not tied to

physiological causes of beha vior and therefore the physiological mechanisms cannot shed

lightonwhetherachoiceisrationalornotin the sense economists use the term. Brain

mechanisms by themselves cannot oﬀer evidence against transitivity of preferences or any

other choice-theoretic assumption. Therefore, evidence that utility maximization is not a

good model of the brain cannot refute economic models.

Discussing decision making under uncertainty, Camerer (2005) writes:

“For example, when economists think about gambling they assume that people combine

the chance of winning (probability) with an expectation of how they will value winning

and losing (“utilities”). If this theory is correct, neuroeconomics will ﬁnd two processes

in the brain — one for guessing how likely one is to win and lose, and another for

evaluating the hedonic pleasure and pain of winning and losing-and another brain

region which combines probability and hedonic sensations. More likely, neuroeconomics

will show that the desire or aversion to gamble is more complicated than that simple

model.”

Camerer assumes that there is one set of correct abstractions for both economics and

neuroscience and tries to identify whether the ones currently used in economics belong to

that set. The conceptual separation between probabilities and utilities is very important for

expected utility theory. This separation need not have a physiological counterpart. Even

if it did, mapping that process into the physiology of the brain and seeing if it amoun ts to

“one [process] for guessing how likely one is to win and lose, and another for evaluating the

hedonic pleasure and pain of winning and losing-and another brain region which combines

probability and hedonic sensations” is a problem for neuroscience, not economics. Since

expected utility theory makes predictions only about choice behavior, its validity can be

assessed only through choice evidence. If economic evidence leads us to the conclusion that

expected utility theory is appropriate in a particular set of applications, then the inability

to matc h this theory to the physiology of the brain might be considered puzzling. But this

puzzle is a concern for neuroscientists, not economists.

Standard economics does not address mental processes and, as a result, economic

abstractions are typically not appropriate for describing them. In his (1998) survey, Rabin

criticizes standard economics for failing to be a good model of the mind, even though

standard economics never had such ambitions:

“Economists have traditionally assumed that, when faced with uncertainty, people cor-

rectly form their subjective probabilistic assessments according to the laws of probabil-

ity. But researchers have documented m any systematic departures from rationality in

judgment under uncertainty.”

Many economists (including the authors of many introductory economic textbooks) are

awarethatmostpeopledonotthinkintermsofprobabilities,subjectiveorotherwise.

Nor does standard economics assume that consumers know Bayes’ law in the sense that a

graduate student in economics would be expected to know it. Economic models connect to

reality through economic variables, prices, quan tities etc. and not through their modeling

of the individual’s decision-making process. Evidence of the sort cited in neuroeconomics

may inspire economists to write diﬀerent models but it cannot reject economic models.

Our central argument is sim ple: neuroscienceevidencecannotrefuteeconomicmodels

because the latter mak e no assumptions or draw no conclusions about physiology of the

brain. Conversely, brain science c annot revolutionize economics because it has no vehicle

for addressing the concerns of the latter. Economics and psychology diﬀer in the question

they ask. Therefore, abstractions that are useful for one discipline will typically be not

very useful for the other. The concepts of a preference, a choice function, dema nd function,

GDP,utility,etc. haveproventobeusefulabstractionineconomics. Thefactthatthey

are less useful for the analysis of the brain does not mean that they are bad abstractions

in economics.

5.2 Mistakes

Individuals sometimes make obviously bad decisions. Neuroeconomists use this fact

as proof of the failure revealed preference theory. Bernheim and Rangel (2005) provide the

following example:

“(...) American visitors to the UK suﬀer numerous injuries and fatalities because they

often look only to the left before stepping into streets, even though they know traﬃc

approaches from the right. One cannot reasonably attribute this to the pleasure of

looking left or to masochistic preferences. The pedestrian’s objectives - to cross the

street safely - are clear, and the decision is plainly a mistake.”

Standard economics has long recognized that there are situations where an outsider could

improve an individual’s decisions. Such situations come up routinely when agents are

asymmetrically informed. Hence, standard economics deals with ‘mistak es’ by employing

the tool of information economics.

Consider the following thought experiment. A prize ($100) is placed either in a red

or in a blue box and the agen t knows that there is a 60% c hance that the money is in the

redbox.Confrontedwithachoicebetweenthetwoboxes,theagentchoosestheredbox.

An observer who has seen that the m oney w as placed in the blue box may think that the

agent prefers choosing red to getting $100. This inference is obviously incorrect because

“choose $100” is a strategy that is not available to the agent. The observer who thinks

the agent prefers red to $100 has not understood the agent’s constraints. Given agent’s

constraints, his choice of the red box is optimal.

Many situations in which agents systematically make mistakes can be interpreted as

situations where agents face subjective constraints on the feasible strategies that are not

apparent from the description of the decision problem. The strategy “only cross the street

when no car is approaching” may be unavailable in the sense that it violates a subjective

constraint on the set of feasible strategies. Hence, a standard economic model of the

street-crossing problem would add a constraint on the set of feasible strategies as part of

the description of the agent.

Suppose the economist asserts that the American tourist prefers not being run over

by a car but ﬁnds it more diﬃcult to implement that outcome in the UK than in the US.

As evidence for this assertion the economist could point to data showing that American

tourists in London avoid unregulated intersections. That tourists incur a cost to cross at

regulated intersections suggests (i) they are unable to safely cross the street withou t help

and (ii) they are not suicidal.

Framing eﬀects can be addressed in a similar fashion. Experimenters can often ma-

nipulate the choices of individuals by restating the decision problem in a diﬀerent (but

equivalen t) form. Standard theory interprets a framing eﬀectasachangeinthesubjective

constraints (or information) faced by the decision mak er. It may turn out that a sign that

alerts the American tourist to ‘look right’ alters the decision even though such a sign does

not change the set of alternatives. The standard model can incorporate this eﬀect by as-

suming that the sign changes the set of feasible strategies for the tourist and thereby alters

thedecision. Withthehelpofthesign,thetouristmaybeabletoimplementthestrategy

“always look right then go” while without the sign this strategy may not be feasible for the

tourist.

For standard economics, the fact that individuals make mistak es is relevant only if

these mistakes can be identiﬁed through economic data. That behavior wou ld have been

diﬀerent under a counter-factual scenario in which the agen t did not make or was preven ted

from making these mistakes, is irrelevant.

6. The Inadequacy of Rationality

Neuroeconomists criticize both standard positiv e economics an d standard normativ e

analysis. In the previous section, we described and responded to the neuroeconomic cri-

tique of positive economics. Here, we address the neuroeconomic critique of normative

economics.

Kahneman (1994) notes that “[t]he term ‘utility’ can be anchored in the hedonic expe-

rience of outcomes, or in the preference or desire for that outcome.” Because agents make

mistakes, neuroeconomists conclude that a person’s choices do not maximize the hedonic

consequences of these c hoices. More generally, neuroeconomists argue that choices do not

maximizing the individual’s well-being or happiness.

The neuroeconomic critique of standard welfare analysis relies on two related argu-

ments: ﬁrst, what people choose often fails to make them happy. Second, proper welfare

analysis should be based on what makes people happy and suc h measurements necessitate

neuroscientiﬁc input. Even if direct measurement of happiness through brain scans is not

yet feasible, neuroeconomists believe that such measurement will eventually be possible.

“A third problem with preferences is that there are diﬀerent types of utilities which

do not always coincide.(...) For example, Berridge and Robinson (1998) have found

distinct brain regions for “wanting” and “liking,” which correspond roughly to choice

utility and experienced utility. The fact that these areas are dissociated allows a wedge

between those two kinds of utility... If the diﬀerent types of utility are produced by

diﬀerent regions, they will not always match up. Examples are easy to ﬁnd. Infants

reveal a choice utility by putting dirt in their mouths, but they don’t rationally antici-

pate liking it. Addicts often report drug craving (wanting) which leads to consumption

(choosing) that they say is not particularly pleasurable (experiencing). Compulsive

shoppers buy goods (revealing choice utility) which they never use (no experienced

utility)(...)” CLP (2004, p. 564).

Neuroeconomists use such evidence and related (thought) experiments to suggest that the

concept of a preference that simultaneously determines behavior and “what is good for the

agent”canbewideoﬀ the mark. Hence, neuroeconomists distinguish between “decision

utilities”, which generate beha vior, and “experienced utilities” which indicate what makes

the agen t happy.

In section 6.2, we discuss and respond to this neuroeconomic critique of standard

welfare analysis. In sections 6.3 and 6.4, we consider two examples of substantive ratio-

nality in the literature: recent proposals for paternalism (section 6.3) and welfare analysis

in multi-self models (section 6.4). First, we provide a brief summary of standard welfare

analysis.

6.1 Standard Welfare Analysis

Economists use welfare analysis to examine how institutions mediate the interests of

the participating individuals. Welfareimprovingchangestoaneconomicinstitutionare

deﬁned to be changes to which the individual(s) would agree. The policy x is deemed better

than the policy y for an individual if and only if, given the opportunity, the individual

would choose x over y.Thechoiceofx over y may be motivated by the pursuit of happiness,

a sense of duty or religious obligation, or reﬂect an impulse. In all cases, it constitutes an

improvement of economic welfare.

Economic welfare analysis is a tool for analyzing economic institutions and models.

For example, economic analysis of a trading institution may establish that the institution

yields Pareto eﬃcient outcomes and, therefore, there is no institutional change that will

improve the economic welfare of all participan ts. Economists view suc h results as successes

of their theories because the results dem onstrate that the economic model of the institution

is “stable”; t here are no chan ges that are mutually agreeable to all participants. Conversely,

models of economic institutions will raise suspicion if there are obvious welfare improving

changes (ch anges that all individuals would agree to) because the availabilit y of such

changes suggests that the model misses important aspects of the underlying reality.

Economists use the revealed preference of individuals as a welfare criterion because it

is the only criterion that can be integrated with positive economic analysis. For example,

consider the economic analysis of farm subsidies. Economists have found that US farm

subsidies are ineﬃcient, i.e., farm subsidies could be eliminated and farmers could be

compensated in a w ay that would increase the economic welfare of all US households. The

most interesting aspect of this observation isthatfarmssubsidiespersistdespitetheir

ineﬃciency. Motivated by this and related observations, economists have examined the

mechanisms (political and economic) that lead to the persistence of ineﬃcient policies.

The example of farm subsidies is typical for the use of welfare analysis in economics.

Normative statements (farm subsidies are ineﬃcient) are used to deﬁne new positiv e ques-

tions (what makes farm subsidies persist?) that lead to better models of the underlying

institution. Economists use welfare analysis to iden tify the interests of economic agents

and to ask whether existing policies can be interpreted as an expression of t hose in terests or

whether the understanding of the institutional constraints on policies remains incomplete.

This use of welfare analysis requires the standard deﬁnition of economic welfare. There

is no reason for economic agents to gravitate towards policies and institutions that yield

higher welfare if the underlying notion of welfare does not reﬂecttheinterestsofagentsas

theagentsthemselvesperceivetheseinterests.

6.2 Neuroeconomic Welfare Analysis

Neuroeconomists treat the economists deﬁnition of welfare as if it were a theory of

happiness and proceed to ﬁnd evidence against this theory. CLP write,

“Economics proceeds on the assumption that satisfying people’s wants is a good thing.

This assumption depends on knowing that people will like what they want. If likes and

wants diverge, this would pose a fundamental challenge to standard welfare economics.

Presumably welfare should be based on ‘liking.’ But if we cannot infer what people like

from what they want and choose, then an alternative method for measuring liking is

needed, while avoiding an oppressive paternalism.” (p. 36)

Welfare in economics is a deﬁnition and not a theory (of happiness). Therefore, the di-

vergence of “liking and wanting” does not pose an y challenge to the standard deﬁnition

of w elfare, no matter how the former is deﬁned. Standard economics oﬀers no substan-

tive criterion for rationalit y because it has no therapeutic am bition; it does not attempt

to cure decision-makers who make choices that do not generate the most pleasure. The

more modest economic deﬁnition of welfare is mandated by the role of w elfare analysis in

economics.

To compare this role with the role envisaged by neuroeconomists, suppose that a

trading institution is found to be (economically) ineﬃcient. Ty pically, this will imply that

someone can set up an alternative institution and make a p ro ﬁt. Hence, we can expect this

change to take place without a benevolent dictator, simply as a result of self-interested

entrepreneurship. Suppose a psychologist argues that an ineﬃcient trading institution

leads to higher ‘experienced’ utility than an eﬃcien t one and agen t s are mistaken in their

preference for the economically eﬃcient institution. Whether or not this assertion is true,

the economic analysis of the trading institution is valid. The economically eﬃcient trading

institution is still the one we can expect to prevail. Moreov e r, since agents perceive their

own interests to coincide with the economic welfare criterion there is no obvious mechanism

(economic or political) by whic h the psychologically superior institution could emerge.

Neuroeconomistswouldarguethateventhoughawelfarecriterionbasedonthein-

dividuals own “preferences or desires” may be relevant for positiv e analysis, a substantive

criterion is needed for normative theory. For neuroeconomists, the goal of welfare analysis

is to advocate changes that improve decision-maker’s well-being. To achieve their goal,

neuroeconomists can either try to convince people to want what is good for them (ther-

apy) or m ake the right choice on their behalf (paternalism). Kahneman (1994) summarizes

both these positions as follows:

“However, truly informed consent is only possible if patients have a reasonable concep-

tion of expected long-term developments in their hedonic responses,... A more contro-

versial issues arises if we admit that an outsider can sometimes predict an individual’s

future utility far better than the individual can. Does this superior knowledge carry a

warrant, or even a duty, for paternalistic intervention? It appears right for Ulysses’

sailors to tie him to the mast against his will, if they believe that he is deluded about

his ability to resist the fatal call of the sirens.”

The neuroeconomic view of welfare analysis builds on an inappropriate analogy between an

economistandatherapist. Itmaybethecasethatsometimesoutsidersknowmoreabout

the future utility of an individual than the individual himself. But the goal of economics

is not to prepare the economist for service at times when he ﬁnds himself in the role of

that outsider.

If economists were in the business of inv estmentcounselling,itmightmakesensefor

neuroeconomists to focus on the conﬂict between what the typical consumer/investor wan ts

to do now and what will make him happ y in the future. But economists do not deal with

patients (or even clients). Therefore it is not clear who the recipient of their counselling

would be. The neuroeconomic view of the economist as a therapist is inapprop riate both

as a description of what economists do, and as a description of what they could be doing.

Of course, one could argue that economists should identify a substantive criterion

for rationality (i.e., a criterion for measuring what really makes individuals happy) and

advocate changes that increase welfare according to this criterion regardless of whether

or not they have the means to convince the potential beneﬁciaries to follow this advice.

The hope being that someone other than the potential beneﬁciary might be convinced

to implemen t the policies. This view is apparent in Kahneman’s search for a benev o lent

paternalistic ﬁgure in his examples:

“...the physician could probably ensure that the patient will retain a more favourable

memory of the procedure by adding to it a medically superﬂuous period of diminishing

pain. Of course, the patient would probably reject the physician’s oﬀer to provide an

improved memory at the cost of more actual pain. Should the physician go ahead

anyway, on behalf of the patient’s future remembering self?” (Kahneman (1994))

Inthesamearticle,Kahneman suggests that there is

“a case in favour of some paternalistic interventions, when it is plausible that the state

knows more about an individual’s future tastes than the individual knows presently.”

When economists or political scien tists model the government, they do so either by endow-

ing the govern ment with certain objectives or by modeling government as an institution

where conﬂicting incen tives of various agents interact. In Kah n em an’s analysis, the gov-

ernment is a benign and disinterested agent whose only role is to serve as the object of the

modeler’s lobb ying eﬀorts.

Welfare analysis for neuroeconomics is a form of social activism; it is a recommendat ion

for someone to change his preferences or for someone in a position of authority to intervene

on behalf of someone else. In contrast, welfare economics in the standard economic model

is integrated with the model’s positive analysis; it takes agents’ preferences as given and

evaluates the performance of economic institutions.

Regardless of one’s views on the importance and eﬃcacy of social activism, there are

advantages to separating the role of the economist as a researcher from the role a particular

economist might play as an advocate. This separation enables the positive analysis to

proceed without having to resolve diﬃcult philosophical problems such as ﬁguring out what

makespeoplehappyorwhoismoredeservingofhappiness. Italsoenablesotherresearchers

to assess and critique a particular piece of analysis without having to evaluate the merits

of the underlying moral philosophy or the eﬀectiveness of the researcher’s activism.

6.3 Proposals for Paternalistic Welfare Criteria

Two recent articles outline plans for welfare economics based on paternalistic princi-

ples. In both papers, the authors are motivated b y evidence showing that the speciﬁcation

of the default option aﬀects individual choices of retirement plans. Rates of enrollmen t in

401(k) plans are signiﬁcantly higher when the default option is to enroll than when the

default option is not to enroll.

A standard interpretation of the 401(k) problem would argue that the default matters

for the decision problem as perceived by the individual. The employee’s set of feasible

strategies changes with the default just as the feasible strategies of the American tourist

in London change when a sign is placed at the side of the road alerting the tourist to look

right. The welfare maximizing default option is the one that agents w ould choose when

asked to choose among defaults.

Thaler and Sunstein (2003) (henceforth TS) seek paternalistic principles for choosing

a default option. TS advocate libertarian paternalism and suggest the follo wing three

guiding principles:

“First, the libertarian paternalist might select the approach that majority would choose

if explicit choices were required and revealed.”

Hence, the libertarian paternalist is to substitute the predicted preferences of the majority

for the preferences of the individual.

“Second, the libertarian paternalist might select the approach that would force people

to make their choices explicit.” Finally, “the libertarian paternalist might select the

approach that minimizes the number of opt-outs.”

TS oﬀer no argumen ts for why their principles are likely to lead to greater happiness.

In fact, they oﬀer no defense of these principles. They simply say that the libertarian

paternalist might choose to use them.

ThefactthattheTSprinciplesarenotparticularly compelling as moral philosoph y

is a side issue. The real issue is that it is diﬃcult to see what question their proposal

addresses. To put it diﬀerently, it is unclear who they have in mind as the potential

beneﬁciary of their ph ilosoph ical argument. The TS motivation for patern alism seems to

be that it is inevitable:

“The ﬁrst misconception is that there are viable alternatives to paternalism. In many

situations, some organization or agent must make a choice that will aﬀect the choices

of some other people.”

Clearly, the decisions of one agent may aﬀect the utility of others. Economic analysis

suggests that the interests of the agent in control are a good place to start when analyzing

such situations. For example, in order to maximize proﬁts, ﬁrms may wish to make their

beneﬁt plans as attractive as possible to their future employees. In that case, ﬁrms will

c hoose plans (and their default options) in accordance with how the emplo yees w ould

choose them. It may be impractical to ask prospective employees about their preferred

default option on the retirement plan and therefore the ﬁrm will use its best subjective

assessment of the employees preferences.

Of course, the employer ma y ha ve diﬀeren t objectives and may choose a plan that

diﬀersfromhisbestguessoftheemployeespreferred plan. Presumably, he would do

so to increase his own welfare. In this situation, as in the situation of the pure proﬁt

maximizing employer, there is no role for the TS principles. The TS argumen t amounts to

telling employers that when they face incomplete informatio n they should adopt a di ﬀerent

objectiv e. Standard economics would predict that employers will take the best action given

their own objectives and given what they know about the preferences of the employees.

In a recent paper, Camerer, Issacharoﬀ, Loewenstein, O’Donoghue and Rabin (2003,

henceforth CILOR) introduce and advocate the notion of “asymmetric paternalism:”

“A regulation is asymmetrically paternalistic if it creates large beneﬁts for those who

make errors, while imposing little or no harm on those who are fully rational.”

CILOR do not explain which preferences reﬂect bounded rationality and which reﬂect full

rationality, when beneﬁts are large and when there is little or no harm. Nevertheless,

their implicit welfare criterion is familiar. As wedescribedinsection5.2,themistakesof

boundedly rational agents can be modeled as a subjectiv e informational constraint facing

these agents. With this re-interpretation, the CILOR principle amounts to an (epsilon)

version of the Pareto principle: help the uninformed without h u rting the informed (too

much). However, there is an important diﬀerence between the CILOR version of the Pareto

principle and the Pareto principle in standa rd economics: CILOR view their principle as

a framework for activism. They urge their readers to adopt their modiﬁed libertarian

philosophy in place of the purely libertarian philosophy that they perceive as guidin g

many economists (and perhaps some lawyers) or the unabashed paternalism favored by

behavioral economists.

“Our paper seeks to engage two diﬀerent audiences with two diﬀerentsetsofconcerns:

For those (particularly economists) prone to rigid antipaternalism, the paper describes

a possibly attractive rationale for paternalism as well as a careful, cautious, and dis-

ciplined approach. For those prone to give unabashed support for paternalistic policies

based on behavioral economics, this paper argues that more discipline is needed and

proposes a possible criterion” (CILOR p. 1212).

Of course, it is legitimate for TS and CILOR to engage employers or the legal and economics

professions in a moral debate. But this has little to do with welfare economics which is not

concerned with moral philosophy or with providing a disciplined guide for social action.

Standard economists spend little time or eﬀort advocating normative criteria even

when they feel that the right normative criterion is unam biguous. For example, many

economists and decision-theorists believe in the importance of making decisions under un-

certainty consistent with some subjective probability assessm ents. Moreover, hardly any-

one would question the normative appeal of using Bayes’ law when updating probabilities.

There are man y research papers where agents are endowed with subjectiv e probabilities

and use Bayes law. The purpose of these papers is not to advocate the use of subjective

probabilities or Bayesian revision; rather, the normative appeal of the Savage model serves

as a starting point for the positive analysis. The ultimate value of Sa vage’s contribution

depends n ot on the ability of his followers to convince individ ual economic agents or benign

planners to adopt his view of probability but on the s uccess his followers have at developing

models that address economic data.

6.4 Preference Reversals and Multiselves

There is evidence that individuals resolve the same intertemporal trade-oﬀ diﬀerently

depending on when the decision is made.

Researchers, starting with the work of Strotz

(1955), have argued that this phenomenon requires modeling the individual as a collection

of distinct selves with conﬂicting interests. Such models represent a major departure from

standard economics conception of the individual as the unit of agency. For example, if the

individual cannot be identiﬁed as a coherent set of interests, then the economists’ welfare

criterion is not well-deﬁned. Hence, for neuroeconomists, preference reversals constitute

an empirical validation of the psychologist’s — as opposed to the economist’s — view of the

individual.

Consid er the following example: in period 1, the agent c hooses the consumption stream

(0, 0, 9) o ver (1, 0, 0) and chooses (1, 0, 0) over (0, 3, 0). Inperiod2theagentchooses(0, 3, 0)

over (0, 0, 9). Suppose the agen t faces the following decision problem: he can either choose

(1, 0, 0) in period 1 or leave the choice bet ween (0, 0, 9) and (0, 3, 0) for period 2. Confronted

with this choice, the agent pic ks (1, 0, 0).

In Gul and Pesen d orfer (2001), (2004) and (2005), we propose a standard, single-self

model that accounts for this behavior. To illustrate the approach, deﬁne C to be the set of

second period choice problems fo r the individual; that is, an element C ∈ C consists of con-

sumption streams with identical ﬁrst period consumption levels: (c

), (c

) ∈

C ∈ C implies c

= c

. In period 2, the individual chooses a consumption stream from

some C. In period 1, the individual chooses a choice problem C for period 2. Choosing

(1, 0, 0) in period 1 corresponds to {(1, 0, 0)} while the option of leaving it to period 2 to

choose between (0, 3, 0) and (0, 0, 9) is described as

C = {(0, 3, 0), (0, 0, 9)}

With this notation, we can summarize the (period 1) behavior as

{(0, 0, 9)}Â{(1, 0, 0)}ÂC = {(0, 3, 0), (0, 0, 9)} ∼ {(0, 3, 0)}

See Loewenstein, et al. for a recent survey of the experimental evidence. In the typical experiment,

subjects choose between a smaller, date 2 reward and a larger, date 3 reward. If the choice is made at

date 2, then the smaller-earlier reward is c hosen. If the choice is made earlier (i.e., at date 1) then the

larger-later reward is chosen. This phenomenon is sometimes referred to as dynamic inconsistency or a

preference reversal.

Note that choosing between {(0, 3, 0)} and {(0, 0, 9)} is not the same as choosing from the

set C = {(0, 3, 0), (0, 0, 9)}. In the former case, the consumer commits toaconsumption

path in period 1 while in the latter he chooses in period 2. The preference statement s

above indicate that the individual prefers a situation where he is committed to (0, 0, 1) to

asituationwherehechoosesfromC in period 2. When such a commitment is una vailable,

and the agent is confronted with C in period 2, he chooses (0, 3, 0).

Standard economic models identify choice with welfare. Therefore, the choice of

(0, 3, 0) from C in period 2 is welfare maximizing as is the choice of {(0, 0, 9)} over {(0, 3, 0)}

in period 1. The interpretation is that, in period 2, the agen t struggles with the temptation

to consume 3 units. Temptation is costly to resist and therefore co nsuming (rather than

holding out for 9 in period 3) is the optimal (and welfare maximizing) choice in period 2.

In period 1, higher period 2 consumption is not temp ting and therefore the agent prefers

{(0, 0, 9)} over {(0, 3, 0)}. Period 1 behavior reveals that the individual’s w elfare is higher

in all periods when he is committed to (0, 0, 9) than when he mu st choose from C in period

The m ulti-self model abandons the revealed preference approach to welfare and con-

structs paternalistic welfare criteria. Consideragainthethreeperiodmodel. Ineachpe-

riod, the individual’s preference are described by a utility function, U

. For concreteness,

assume:

)=c

+ βδc

+ βδ

)=c

+ βδc

)=δc

(9)

where δ = β =1/2. While diﬀerent papers postulate diﬀerent w elfare criteria for such

situations, the common argument is that preference reversals necessitate a criterion for

trading-oﬀ the utility of the various selv es. The most common practice in this literature

is to treat the U

below as the welfare criterion.

)=c

+ δc

+ δ

Note that choosing between {(0, 0, 9)} and C is not a feasible option in period 2. Therefore, revealed

preference experiments cannot uncover whether or not in period 2, the individual has a preference (or

distaste) for commitment.

This particular welfare criterion may seem odd. After all, U

quite arbitrarily sets β =1

and assigns a higher welfare to (1, 0, 11) than to (2, 3, 0) even though selves 1 and 2 prefer

(2, 3, 0). The multiple-selves literature interprets U

as the preferences with the“present

bias” removed.

In other words, β<1 is diagnosed as a defect and the role of policy

intervention is to cure this defect.

Note that hyperbolic discounting (or time inconsistency) is not necessary for gener-

ating conﬂict among the various selves of the individual: Consider again the three pe-

riod example above but now let β = 1. The resulting utilit y functions describe stan-

dard preferences with exponential discounting. Consider the two consumption streams:

(1, 0, 0) and (0, 0, 4) and note that U

(1, 0, 0) = U

(0, 0, 4) but U

(1, 0, 0) <U

(0, 0, 4) and

(1, 0, 0) <U

(0, 0, 4); that is, the allocation (1, 0, 0) is Pareto dominated by the allo-

cation (0, 0, 4) even though the usual w elfare criterion of the multiselves literature (U

)

would deem the two alternatives welfare equivalent.

Economists often note the arbitrariness of using U

as a welfare criterion in the mul-

tiselves model. It is not clear what hedonic utility calculations ha ve led neuroeconomists

to decide that U

represents the right trade-oﬀ among the hedonic utilities of the various

selves. Our point is diﬀerent: standard economics has neither need nor use for a wel-

fare criterion that trades oﬀ utility among the various selves of a single individual. Suc h

trade-oﬀs can never play a role in explaining or understanding economic institutions. By

deﬁnition, only behavior can inﬂuence economic data or institutions. Hence, beyond their

eﬀect on behavior the various ‘selves’ are irrelevan t for the analysis. By contrast, neu-

roeconomists view the existence of multiple selves as both an opportunity and a rationale

for activism. They wish to urge the individual to do a better job at accommodating the

welfare of their future selves (i.e., resist β<1 and other biases). Failing that, they would

like to convince third parties to intervene on behalf of the agent’s future selves. This ther-

apeutic/paternalistic stance is sim ilar to the position of medical professionals who attempt

to cure a patient’s addiction. By proposing a welfare criterion, the modeler is either urging

See, for example, Rabin and O’Donoghue (2003).

In standard analysis, this issue does not arise because the same utility function (U

)isusedto

describe behavior (and welfare) at each decision date. In period 2, period 1 consumption cannot be altered

and therefore the additively separable form of the utility function allows us to drop the ﬁrst term as a

simpliﬁcation without aﬀecting optimal choices.

the individual to reform his behavior, or urging someone in a position of authority to force

theindividualtodoso.

Identifying what makes people happy, deﬁning criteria for trading-oﬀ one person’s

(or selves) happiness against the happiness of another, and advocating social change in a

manner that advances overall happiness by this criterion is a task many neuroeconomists

ﬁnd more worthy than dealing with the more pedestrian questions of standard economics.

Ho wever, the expression o f this preference constitutes neither an empirical nor a method-

ological criticism of standard economics.

7. The Uniﬁcation of Economics and Neuroscience

Neuroeconomists often cite improvements in neuroscience, in particular, improvements

in measurements, as a central reason for unifying the disciplines of economics, psyc h ology,

and brain science:

“Since feelings were meant to predict behavior, but could only be assessed from behav-

ior, economists realized that without direct measurement, feelings were useless inter-

vening constructs. In the 1940s, the concepts of ordinal utility and revealed preference

eliminated the superﬂuous intermediate step of positing immeasurable feelings. Re-

vealed preference theory simply equates unobserved preferences with observed choices.

Circularity is avoided by assuming that people behave consistently, which makes the

theory falsiﬁable; once they have revealed that they prefer A to B, people should not

subsequently choose B over A...... The ‘as if’ approach made good sense, as long as

the brain remained substantially a black box. The development of economics could not

be held hostage to progress in other human sciences. But now neuroscience has proved

Jevons’ pessimistic prediction wrong; the study of the brain and nervous system is

beginning to allow direct measurement of thoughts and feelings.” (CLP (2005), p. 10).

Thus, neuroeconomists view the revealed preference approach to be an outdated concession

to technological limitations of the past.

Since the technology for distinguishing bet ween

“liking” (i.e., a criterion of substantive rationality) and “wanting” ( i.e., ch oice) may soon

For Kahneman, the rejection of hedonic utility as the basis for economic analysis of decisions has less

to do with tec hnology than the adherence to an outdated philosoph y of science. Rabin (1996) seems to view

a doctrinaire obstinacy as the only explanation for the persistence of economists’ “habitual” assumptions.

be available, econo mics (and presumably other social sciences) should abandon the revealed

preference methodology and adopt the methodology of psychology and neuroscience.

The dominant role of revealed preference analysis in economics has little to do with

technology. Economic phenomena consist of individual choices and their aggregates and

do not include hedonic values of utilities or feelings. Therefore, it is not relevant for an

economic model to explore the feelings associated with economic choices. The poin t of

revealed preference theory is to separate the theory of decision making from the analysis

of emotional consequences of decisions. This separation is useful whether or not emotions

can be measured simply because it facilitates specialization. Note that the m ore detailed

and sophisticated the measurement the greater is the poten tial beneﬁt of specialization.

Brain imaging data are of a radically diﬀerent form than typical economic data. If

the prediction of great advances in brain science turn out to be correct, they will certainly

be accomp anied by theoretical advances that address the particular data in that ﬁeld. It

is unreasonable to require those theories to be successful at addressing economic data as

well. By the same token, the requirement that economic theories simultaneously account

for economic data and brain imaging data places an unreasonable burden on economic

theories.

Note that the above does not say that psyc hological factors are irrelevant for economic

decision making, nor does it say that economists should ignore psychological insights.

Economists routinely take their inspiration from psychological data or theories. However,

economic models are evaluated by their success at explaining economic phenomena. Since

hedonic utility values or brain imaging data are not economic phenomena, economists

should not feel constrained to choose models that succeed as models o f the brain.

The arguments advanced by neuroeconomists in favor of uniﬁcation often fail to dis-

tinguish between a novel philosophical position and a scientiﬁc breakthrough. Often, what

neuroeconomists present as an empirical challengetoeconomicsisbestviewedasaninvi-

tation to an ethical debate. For example, Kahneman (1994) writes:

“The history of an individual through time can be described as a succession of separate

selves... Which one of these selves should be granted authority over outcomes in the

future?”

Hence, neuroeconomics interprets the individual as a ﬂawed and inconsistent sequence of

“pleasure mac hines,” that need therapeutic and paternalistic assistance for assessing the

right intertemporal trade-oﬀs and making the right choices.

It is not clear what evidence neuroeconomics can oﬀer to answer questions like “should

physicians increase the actual pain experienced by the patient in order to facilitate his

memory and improve his decision making for the future?” (Kahneman (1994)). What is

clear is that ﬁnding out how to trade-oﬀ the welfare of one self against another or deciding

“[w]hich one of these selves should be granted authority over outcomes in the future,” is

notaneconomicproblem.

CLP (2004) suggest a more modest goal: that neuroscience may facilitate direct mea-

surement of preference parameters by “asking the brain, not the person,” (p. 573). The

authors hav e no example of observing a choice parameter — such as the coeﬃcient of rel-

ative risk aversion or the discoun t factor — through brain imaging, no suggestions as to

how such inference could be done. They oﬀer no criteria for distinguishing a brain where

δ = .97 versus one where δ = .7. They do not explain what language to use when ‘asking

the brain, rather than the person,’ which language the brain will u se to respond, or what

to do when the brain’s answer conﬂicts with the answ er of the person.

In the end, scien tiﬁc dev elopments pla y a small role in the arguments of neuroe-

conomists: when it comes to substantiating the central philosophical position that there is

adiﬀerence between what people want and what is good for them, subjective readings of

the facial expressions of mice do just as w ell as anything that might be learned from fMRI

readings.

8. Conclusion: Why the Neuroeconomics Critique Fails

Kahneman (1994) notes the following two problems facing “a critic of the rationality

assumption”:

“...(ii) a willingness of choice theorists to make the theory even more permissive, as

needed to accommodate apparent violations of its requirements; (iii) a methodological

position that treats rationality as a maintained hypothesis making it very diﬃcult to

dispr ove....”

Kahneman’s observations make it clear that rationality is not an assumption in economics

but a methodological stance. This stance reﬂects economists’ decision to view the indi-

vidual as the unit of agency and in vestigate the interaction of the purposeful behaviors of

diﬀerent individuals within various economic institutions. One can question th e usefulness

of this methodological stance by c h allenging individual economic models or the combined

output of economics but one cannot disprove it.

The diﬃculties that Kahnem an observes for critics of the rationality assumption are

no diﬀerent than the diﬃculties that one would encounter when c hallenging the assump-

tion that laboratory experimen t s on individual choice are useful for understanding real-life

behavior. For example, a critic of such experiments may complain that real-life choice

problems do not come with explicit probabilities. If successful, such a criticism will lead

to a new class of experiments, ones that do not make explicit references to probabili-

ties.

However, a critic cannot expect to dispro ve the usefulness of experimental methods

for understanding c hoice behavior. Criticisms that aim to disprove a broad and ﬂexible

methodology as if it were a single falsiﬁable assumption are best viewed as demands for

a shift in emphasis from questions that the critic considers uninteresting to ones that he

ﬁndsmoreinteresting.

This latter description ﬁts our view of what CLP (2005), Rabin (1998), and Kahneman

(1994) describe as the radical challenge to economics:

“The radical approach involves turning back the hands of time and asking how eco-

nomics might have evolved diﬀerently if it had been informed from the start by insights

and ﬁndings now available from neuroscience. Neuroscience, we will argue, points to

an entirely new set of constructs to underlie economic decision making. The standard

economic theory of constrained utility maximization is most naturally interpreted ei-

ther as the result of learning based on consumption experiences (which is of little help

when prices, income and opportunity sets change), or careful deliberation- a balancing

of the costs and beneﬁts of diﬀerent options — as might characterize complex decisions

like planning for retirement, buying a house, or hammering out a contract. Although

economists may privately acknowledge that actual ﬂesh-and-blood human beings often

Compare for example, earlier experiments on the Allais’ Paradox and the common ratio eﬀect with

later experiments on framing and reference points.

choose without much deliberation, the economic models as written invariably represent

decisions in a ‘deliberative equilibrium,’ ...” (CLP (2005), p. 10).

Populating economic models with “ﬂesh-and-blood h uman beings,” was never the objective

of economists. Constrained optimization, Bayes law, and oth er economic abstractions do

not represent the state-of-the art psychology of an earlier era. Therefore, there is no reason

to believe that making the state-of-the art psychology of our time available earlier would

have had such a profound eﬀect on the development of economics.

Rabin (1998) argues that

“it is sometimes misleading to conceptualize people as attempting to maximize a co-

herent, stable, and accurately perceived U(x).”

Economists have at their disposal numerous devices to incorporate instabilit y (or change)

into individual preferences. They can assume that the decision-maker’s preferences de-

pend on an exogenous state variable, on the information of his opponen ts, or his own

consumption history. The decision-maker ma y be learning about a relevant preference pa-

rameter, over time. All this ﬂexibility or permissiveness not withstanding, it is likely that

the economists’ model of the individual is not suitable for psyc hologists’ goals. It does not

follow from this that economists should adopt both the goals and methods of psychology.

Regardless of the source of their inspiration, economic models can only be evaluated

on their own terms, with respect to their own objectives and evidence. A revolution in eco-

nomics has to yield great economic insights. The CLP and Rabin agendas seem far reach-

ing only because they deﬁne the task of economics as contin ually importing psychology-

neuroscience ideas. Both papers oﬀer ve ry little in the way of nov el economic analysis

or implications. Rabin observes that “...fairness and reference-level eﬀects (reviewed in

Section 2) and framing eﬀects (reviewed in Section 4) are likely to contribute to downward

stickiness in wages” but leaves “it for other forums to explore these implications.” Simi-

larly, all the c hallenges CLP (2005) identify for the emerging discipline of neuroeconomics

resemble the current questions of psycholo gy more than the current questions of econ om i cs.

A choice theory paper in economics must identify the revealed preference implications

of the model presented and describe how revealed preference methods can be used to iden-

tify its parameters. Rev ealed preference earnssuchacentralroleineconomicsbecausethis

istheformofevidencethatisavailabletoeconomists-andnotbecauseofaphilosophical

stance against other forms of evidence.

Greater p sychological realism is not an appropriate modeling criterion for economics

and therapeutic social activism is not its goal. Welfare analysis helps economists under-

stand how things are by comparing the existing situation to how things migh t hav e been

in a plausible alternative institutional setting; w e lfare theory is not a blueprint for a social

mo vemen t.

We ma y be sceptical of neuroscien tists’ ability to come up with a univ ersal, physio-

logically grounded criteria for measuring happiness. We may also have doubts about the

potential eﬀectiveness of neuroeconomists at convincing individuals or society as a whole,

to adopt policies that increase “total happiness” by their measure. Our response to the

neuroeconomics welfare theory is simpler: such a combination of moral philosop hy and

activism has never been the goal of economics; grounding this combination in biology is

unlikely to make it so.

9. Appendix

Proof of the Proposition

First, we will show that (i) implies (ii): Suppose c is a general K¨oszegi-Rabin choice

function. Then, there exists a reference dependent utility function U such that c = C(·,U).

Deﬁne º as follows: x º y if U(x, x) ≥ U(y, x). Then, for all A ∈ Y ,

c(A)=C(A, U)={x ∈ A | U(x, x) ≥ U(y, x)} = {x ∈ A | x º y} = C

(A)

as desired.

To pro ve that (ii) implies (iii), assume that c = C

and let n be the cardinality of X.Recall

that º is a c omplete, reﬂexive, binary relation. We write x Â y for x º y and y 6º x.Let

K = X × X.Fork =(w, z) ∈ K,wedeﬁne the function u

(w,z)

: X → {−2, 0, 2, 3} as

follows:

(w,z)

(x)=











3ifx = w = z

2ifx = w and w Â z

−2ifx = z and w Â z

0otherwise.

Deﬁne the function µ as follows:

µ(t)=

16nt if t ∈ {−4, −3, 4}

t if t ∈ {−2, 0, 2, 3}

Clearly, µ is strictly increasing and µ(0) = 0. Let

U(x, y)=

k∈K

(x)+

k∈K

µ(u

(x) − u

(y))

To complete the proof, we will show that C

= C(·,U); that is x º y iﬀ U(x, x) ≥ U(y, x)

for all x, y ∈ X,and

U(x, y) ≥ U(y, y)impliesU(x, x) >U(y, x)(4)

Note that

2n ≥

k6=(x,x)

(x) ≥−2n (∗)

Let K

x,y

= K\{(y, y), (x, x), (x, y), (y, x)} andnotethatfork ∈ K

x,y

2 ≥ u

(x) − u

(y) ≥−2(∗∗)

Equations (*) and (**) and the deﬁnition of µ imply that

4n ≥

x,y

(x) − u

(y)) =

x,y

µ(u

(x) − u

(y)) ≥−4n

Let x º y.Notethatµ(u

(x,y)

(y)−u

(x,y)

(x)) ≤ 0and,sincex º y,wealsohaveµ(u

(y,x)

(y)−

(y,x)

(x)) ≤ 0. It follows that

U(x, x) − U(y, x)=

k∈K

(x) − u

(y)) −

k∈K

µ(u

(y) − u

(x))

≥−4n −

x,y

µ(u

(x) − u

(y))−

− µ(u

(x,x)

(y) − u

(x,x)

(x)) − µ(u

(y,y)

(y) − u

(y,y)

(x))

≥−8n +48n − 3 > 0

Conversely, let y Â x. Then, µ(u

(x,y)

(y)−u

(x,y)

(x)) = 0 and µ(u

(y,x)

(y)−u

(y,x)

(x)) = 64n.

Therefore,

U(x, x) − U(y, x)=

k∈K

(x) − u

(y)) −

k∈K

µ(u

(y) − u

(x))

≤ 4n −

x,y

µ(u

(y) − u

(x)) − µ(u

(x,x)

(y) − u

(x,x)

(x))

− µ(u

(y,y)

(y) − u

(y,y)

(x)) − µ(u

(y,x)

(y) − u

(y,x)

(x))

≤ 8n − 3+48n − 64n<0

Finally, suppose U(x, y) − U(y, y) ≥ 0. Then,

U(x, x) − U(y, x) ≥ U(x, x) − U(y, x) − U(x, y)+U(y, y)

= −

k∈K

[µ(u

(y) − u

(x)) + µ(u

(x) − u

(y))]

= −2(µ(−3) + µ(3)) = 2(48n − 3) > 0

completing the proof that (ii) implies (iii). That (iii) implies (i) is immediate.

References

1. Bernheim, B. D. and A. Rangel, 2004. “Addiction and Cue-Conditioned Cognitive Pro-

cesses,” American Economic Review, 94(5): 1558—90.

2. Caplin A, and J. Leahy, 2001. “Psychological Expected Utility Theory and Anticipatory

Feelings,” Quarterly Journal of Economics, 2001, 55—80.

3. Camerer, Colin F., George Loewenstein and Drazen Prelec, 2005. “Neuroeconomics:

Ho w neuroscience can inform economics.” Journal of Economic Literature,Vol.34,No.1.

4. Camerer, Colin F.; George Loew enstein; and Drazen Prelec, 2004. “Neuroeconomics:

Why economics needs brains.” Scandinavian Journal of Economics, 2004, Vol. 106, no. 3,

555—79.

5. Camerer, Colin; Sam uel Issac haroﬀ;GeorgeLoewenstein;TedO’Donoghue;andMatthew

Rabin, 2003. “Regulation for conservatives: Beha vioral economics and the case for ‘asym-

metric paternalism’.” Univ. Penn. Law Review, Vol. 151, 2111—1254.

6. Epstein, L. and S. Zin, 1989. “Substitution, Risk Aversion, and the temporal Behavior

of Consumption and Asset Returns: A Theoretical Framework,” Econometrica 57, 937-69.

6. Epstein, L. and S. Zin, 1991. “Substitution, Risk Aversion, and the temporal Behavior

of Consumption and Asset Returns: An Empirical Analysis,” Journal of Political Economy

99, 2, 263-86.

7.Frederick,S.,G.Loewenstein,T.O’Donoghue,“TimeDiscountingandTimePreference:

A Critical Review” Journal of Economic Literature, 2002, XL (2): 351—402.

8.Gruber,J.andB.K¨oszegi, “Is Addiction “Rational”? Theory and Evidence”, Quarterly

Journal of Economics, 2001: 1261—1303.

9. Gul, F. and W. Pesendorfer, “Temptation and Self-Control,” Econometrica, 2001, 69(6):

1403—1436.

10.Gul,F.andW.Pesendorfer,2004.“Self-Control and the Theory of Consumption,”

Econometrica.

11.Gul,F.andW.Pesendorfer,2005.“TheRevealedPreferenceTheoryofChanging

Tastes”, Review of Economic Studies.

12.Hsu,MingandCamerer,ColinF.,2004,Ambiguity-Ave rsion in the Brain. Caltech,

Working Paper.

13. Kahneman, D., 1994. “New challenges to the rationality assumption.” Journal of In-

stitutional and Theoretical Economics, 150, 18—36.

14.Kreps,D,1979.”APreferenceforFlexibility”,Econometrica, 47: 565—576.

15. Kreps, D. and E. L. Porteus, 1978. “Temporal Resolution of Uncertainty and Dynamic

Choice Theory,” Econometrica.

16. Koszegi, B. and M. Rabin, 2004. “A Model of Reference-Dependent Preferences,”

mimeo.

17. Laibson, D., 1997. “Golden Eggs and Hyperbolic Discoun t ing,” Quarterly Journal of

Economics, 112: 443—477.

18. Laibson, D avid. 2001. A Cue-Theory of Consumption. The Quarterly Journal of Eco-

nomics, 116(1): 81—119.

19. Loewenstein, G., 1996. “Out of Control: Visceral Inﬂuences on Beha vior,” Organiza-

tional Behavior and Human Decision Processes, 65, 272—292.

20. Loewenstein, G. and D. Prelec, “Anomalies in Intertemporal Choice,” Quarterly Jour-

nal of Economics, 1992, 107, 573—597.

21. O’Donoghue and Rabin, “D oing it Now or Later,” American Economic Review, 1999,

89(1): 103—124.

22. O’Donoghue and Rabin, “Studying Optimal Paternalism, Illustrated with a Model of

Sin Taxes,” American Economic Review Papers and Proceedings, May 2003, 93(2), 186—

191.

23. Rabin M., “A Perspective on Psyc hology and Economics,” European Economic Review,

forthcoming, 2002.

24. Rabin M., “Psychology and Economics,” Journal of Economic Literature, 36, pp. 11—46,

March 1998.

25. Strotz, R. H., 1956. “Myopia and Inconsistency in Dynamic Utility Maximization,”

Review of Economic Studies, 23(3): 165—180.

26. Thaler, R., 1980. Towards a positive theory of consumer choice. Journal of Economic

Behavior and Organization, 1, 39—60.