Evaluating Common FuturesRethinking Prescriptivism and Descriptivism

Kian Mintz-Woo

CCFC2015

UNESCO—July 10, 2015

2

• Cost Benefit Analyses addresses trade-offs

btw. present & future consumption

• This often involves determining the

contribution of consumption to utility η;

equivalently, curvature of utility function

• I introduce two worries for assigning a value to

this parameter stemming from behavioral

psychology

Evaluating Climate Policies

3

• In IPCC SAR WG3, Arrow et al. (1996) called

the methodologies descriptivism and

prescriptivism (cf. Manne 1995)

• Descriptivists think we should assign values to

normative parameters (e.g. η) by aggregating

actual revealed, or stated, preferences

(Nordhaus)

• Prescriptivists think ethical theorizing

unavoidable so it should be explicit (Broome,

Stern, Dasgupta)

Descriptivism/Prescriptivism

4

• Prospect theory tells us that

decisions elicited under risk will

be irrational in a predictable way

• Kahneman and Tversky (1979)

tells us that individuals judge

gains and losses asymmetrically, with (1)

different concavity and (2) non-differentiability

about the origin

Prospect Theory

5

Thus, prospect theory

generates “normatively

unacceptable consequences,

such as inconsistences,

intransitivites, and violations of dominance”

(Kahneman 1979, p. 277)

A Problem for Descriptivists

6

• So any decisions elicited under risk will

be non-evaluative

• But this is a problem; any

savings/investment behavior is under

risk!

A Problem for Descriptivists

7

• One might thus adopt expert judgment

• On this view, economists or philosophers

make social judgments about the value of

parameters like η

Prescriptivism

8

• Behavioral psychologists tell us that, for target

questions that require complex, abstract

thought, one may substitute heuristic

questions

Heuristic Questions

9

“How happy are you with

your life these days?”

A Target Question

10

“What is my mood right

now?”

A Heuristic Question

11

“How much would you

contribute to save

endangered species?”

Another Target Question

12

“How much

emotion do I

feel when I

think of dying

dolphins?”

Another Heuristic Question

13

Choosing values of η fits all of these

criteria:

• it is difficult;

• there is an obvious emotionally valenced

heuristic (Finucane 2000);

• and there is no simple check

A Problem for Prescriptivism

14

• So the target question:

“What is the elasticity of

marginal utility of

consumption η?”

A Problem for Prescriptivism

15

…could be replaced by:

“How do I feel when I

imagine having different

levels of consumption?”

A Problem for Prescriptivism

16

• If we take these strains of psychology

seriously, they undermine judgments of η on

both the descriptivist and the prescriptivist

views

• They will give us distorted results from

prospect theory, or mere heuristics

• What should we do? I think we should hold

our value judgments for η a less securely

Conclusion