Judgmental Discounting and Environmental Risk Perception ...

Journal of Social Issues, Vol. 63, No. 1, 2007, pp. 21--39
Judgmental Discounting and Environmental Risk
Perception: Dimensional Similarities, Domain
Differences, and Implications for Sustainability
Alexander Gattig ∗
University of Bremen
Laurie Hendrickx
University of Groningen
Environmental risks constitute a special category of risks because they often involve
consequences that are highly uncertain, strongly delayed, occurring at distant
places, and—therefore—mostly borne by others. Economic, decision–theoretic,
and psychological research about the way people deal with such consequences is
reviewed. Two major findings are presented: first, there is evidence that discounting
mechanisms are stable across different preference dimensions (uncertainty,
temporal, spatial, and social distance). Second, discount rates tend to vary across
different problem domains (e.g., environmental vs. health vs. financial risks). In
particular, it appears that temporal discounting is less pronounced for environmental
risks than in other domains. Several factors are identified that affect the nature
of the risk evaluation process, and it is argued that environmental risks differ from
other risks on such factors. These environmental-risk characteristics may have important
implications for policy strategies to promote environmental sustainability.
Contrary to other domains, appealing to the public’s long-term preferences may
be successful. Also in policy making, insights from standard economic decision
theory to environmental decision making should be applied with caution.
Environmental Risks and Discounting Processes
Understanding how people perceive, evaluate, and deal with environmental risks
is essential for achieving environmental sustainability. People’s environmentally
∗Both authors contributed equally to this paper. Correspondence concerning this article should be
addressed to Alexander Gattig, Jean Monnet Centre for European Studies CEuS, University of Bremen,
SFG, Enrique-Schmidt-Strasße 7, 28359 Bremen, Germany. [E-mail: gattig@empas.uni-bremen.de].
21
C○ 2007 The Society for the Psychological Study of Social Issues

22 Gattig and Hendrickx
relevant behaviors and their support for policy measures aimed at environmental
sustainability depend—among other factors (see Lindenberg & Steg, this issue)—
on the extent to which they consider environmental problems, such as air pollution,
soil contamination, or global warming, to be a risk. In this article the term risk
refers to a situation or development that may result in negative consequences. 1
However, environmental risks seem to constitute a special category of risks.
They often are characterized by high levels of uncertainty, by strongly delayed consequences,
and by consequences that occur at distant places and are—therefore—
borne by others. All of these aspects may result in a discounting of such risks;
that is, such risks are taken less seriously than risks with negative outcomes that
occur for sure, now, here, and to us. When dealing with environmental risks, it is
frequently necessary to balance benefits that occur for sure, immediately, here, and
to ourselves against losses that are uncertain, delayed, might occur elsewhere, and
to others. Heavily discounting such losses (i.e., considering them as less serious)
may result in decisions and behaviors that are incompatible with environmental
sustainability.
The difficult relationship between sustainability and discounting processes is
captured in the commons dilemma paradigm (see also Vlek & Steg, this issue).
In the so-called tragedy of the commons (Hardin, 1968) several farmers share a
piece of grassland. Each farmer has an incentive to add cattle to this grassland
because (s)he solely reaps the benefits (his/her cattle is nourished) while the costs
(depletion of the land) are borne by all farmers. Here, realizing sure short-term
benefits occurring directly to the decision maker results in an overexploitation of
the commons, eventually leading to its ruin in the long run.
Human decision-making centers on outcomes that occur to us, here, now, and
for sure. Consequences that deviate in one or more of these aspects are valued
less, that is, they tend to be discounted. When dealing with environmental risks
in general and common-pool resources in particular, often such consequences
are involved (see Jager & Mosler, this issue, for an elaboration and for examples
showing how these consequences may affect behavior). For instance, in the tragedy
of the commons benefits do occur here and now, for sure, and directly to the
decision maker, while costs to a large extent are delayed, unsure, and borne by
others. Hence, discounting potentially complicates dealing with environmental
risks in general and it worsens the tragedy of the commons. In this article we
investigate and compare the discounting processes involved in such environmental
risk evaluations and we explore their implications for environmental sustainability.
1 In the economic and decision-theoretic literature the term risk is reserved for cases where either
positive or negative outcomes occur with a probability that is known by the decision maker. Uncertainty
on the other hand refers to choices where these probabilities are unknown. Contrary to this use – and in
line with what is customary in risk perception research – we speak of a risk when we refer to situations
that may result in negative outcomes and we consider uncertainty to be a preference dimension, that
is, an outcome characteristic that affects people’s preferences.

Discounting and Environmental Risk Perception 23
Generalizability of Judgmental Discounting Across Dimensions
Much research, mostly in economics and psychology, has been devoted to
the study of how people perceive, evaluate, and deal with uncertainty. In the last
two decades, research on intertemporal choices has also flourished, again mainly
in psychology and economics. For both preference dimensions, that is, outcome
characteristics that affect people’s preferences (see note 1), standard economic
theorizing has yielded a set of normative requirements (axioms) whose acceptance
by the decision maker implies rational, outcome-maximizing behavior. However,
a plethora of empirical studies has revealed violations of the axioms underlying the
respective models, as well as of their implications (for overviews see Frederick,
Loewenstein, & O’Donoghue, 2002; Kahneman & Tversky, 1979; Tversky &
Kahneman, 1992). Economists call such deviations of (implications of) the standard
economic theory anomalies.
In response to these empirical challenges, several attempts were undertaken
to develop descriptive theories accounting for anomalies with regard to choices involving
uncertainty and with regard to choices involving temporal delay. However,
although the nature of the axiomatic systems underlying the standard economic
theories on uncertainty and temporal delay is very similar, few authors have taken
into account the similar nature of the observed anomalies (e.g., Prelec & Loewenstein,
1991; Quiggin & Horowitz, 1995), have generalized empirical results to
other preference dimensions (e.g., Björkman, 1984; Rachlin & Rainieri, 1992),
or have imported insights from other domains into their own field of interest (see
Laibson, 1997, for an exception).
In the majority of both economic and psychological studies, subjects were
asked to choose between varying amounts of money available either with different
probabilities and/or at different points in time. Typical examples are choice options
such as “What would you prefer: (A: an amount x with a probability of .5 in 4 weeks)
or (B: an amount x/2 for sure now)?” Although the majority of studies involve
hypothetical choice situations, their main findings were confirmed in studies that
used real rewards and real choices (e.g., Kachelmeier & Shehata, 1992; Kagel &
Roth, 1995, provide an overview and a discussion concerning the robustness of
such experiments).
Two other preference dimensions that may affect people’s risk perception and
evaluation are the spatial and social distance of the negative outcomes. However,
research about the role of these dimensions in environmental risk perception and
decision making is sparse. Sociologists and psychologists have developed several
conceptions of social distance (see already Bogardus, 1959) and social comparison
but provided few links to choice behavior. Research on social orientation and its
consequences for choices in social dilemmas (e.g., Liebrand, Messick, & Wilke,
1992) and on the effect of altruism in ultimatum games (Charness & Rabin, 2002)
has been carried out rather extensively by psychologists and economists alike, but

24 Gattig and Hendrickx
these findings are generally not related to environmental decision making or the
commons dilemma. However, some links have been made, mainly in research on
risk perception, between the discounting of spatially distant outcomes and decision
theory (see Vlek & Keren, 1992, for an overview). Although Vlek and Keren
suggest that the utility of spatially distributed outcomes could be assessed in a way
similar to the assessment of temporally distributed outcomes, they (1992, p. 267)
state: “Decision–theoretic research on spatial dilemmas and preferences is highly
underdeveloped.” Recently, research interest with respect to this area has risen
and problems like the not-in-my-back-yard (NIMBY) phenomenon have received
considerable attention, for instance by Frey, Oberholzer-Gee, and Eichenberger
(1996).
The only research on discounting in which uncertainty, temporal delay, spatial
distance, and social distance were studied simultaneously was conducted by
Gattig (2002, Chapter 7). There, subjects repeatedly chose between two options,
each of which consisted of a monetary outcome 2 and some value on one of the
four outcome dimensions studied (uncertainty, temporal delay, spatial distance,
and social distance). The first three outcome dimensions could be easily quantified,
by providing subjects with information, respectively, about the probability,
temporal delay, and spatial distance of the outcome. In contrast, social distance
does not easily lend itself to such quantification. Gattig (2002) created fictive
characters, defined by five important though not exhaustive characteristics: age,
socioeconomic status, hobbies, nationality, and political orientation. Numerical
social distance scores depended on how much each character differed from the
“average subject” for all five characteristics; the empirical validity of this assessment
was checked and confirmed separately. Characters were supplemented by
photos and differed for male and female subjects, male subjects being presented
with male characters and female subjects being presented with female characters.
To give an example, for male student subjects, the closest character was a 24-year
old, left-wing student who played soccer. These attributes summed up to a specific
number of points (the highest possible). The number of points attributed to other
characters differed according to which and how many of these attributes were
varied. Subjects were confronted with a variety of choices such as the following:
Example of intertemporal choice:
“Imagine you have to choose between the following two options:
A) A loss of Dfl 100 in 8 weeks3 .
B) A loss of Dfl 110 in 12 weeks.
2 For the choice problems dealing with spatial distance, monetary rewards were replaced by supermarkets
and small shops varying with respect to the number of items-in-store.
3 Dfl refers to the Dutch currency before the introduction of the Euro (Dfl 100 ≈ €45).

Discounting and Environmental Risk Perception 25
Which Option Do You Prefer?”
Example of interpersonal choice:
“Please read the descriptions of Willem (being presented as more similar to the
subject) and Leo given in the appendix carefully. Imagine the following two events:
A) Willem wins Dfl 150.
B) Leo wins Dfl 200.
Which Event Would You Prefer?”
Within these choices monetary outcome values and the value of the outcome
dimension studied were simultaneously varied in the following ways: monetary
gains versus losses, multiplying both monetary outcome values with a common
factor, adding a common constant to both monetary outcome values, multiplying
the value of the outcome dimension in both options with a common factor, and
adding a common constant to the value of the outcome dimension in both options.
In previous research on choice under uncertainty and intertemporal choice, these
manipulations generally caused changes in preferences between options in the
following ways (see Prelec & Loewenstein, 1991):
a) Multiplying the value of an outcome–characteristic by a common factor in
both options raises the importance of that characteristic for people’s choices
(“common ratio effect”).
b) Adding a common constant to the value of an outcome–characteristic in both
options lowers the importance of that characteristic (“common difference effect”).
c) Changing the value of an outcome-characteristic from positive to negative raises
the importance of that characteristic (“sign effect”).
Special cases of these regularities are the so-called certainty effect in choice under
uncertainty and the immediacy effect in intertemporal choice: a decision maker
is most sensitive to uncertainty and delay when they are introduced, that is, if an
uncertain or delayed option is compared with a sure or an immediate option. If
the same amount of uncertainty or the same delay is added to an already uncertain
or delayed option, a decision maker’s behavior will be affected much less. Gattig
(2002) demonstrated that these behavioral regularities apply to the discounting of
uncertain, delayed, spatially, as well as socially distant outcomes. Moreover, the
discount functions for the respective preference dimensions appear to have similar
(negatively accelerated) forms. To give an example, Gattig (2002) reports substantial
changes in preference when rewards became more delayed (56.4% preferred
the sooner option when time delays were “now” and “in 4 weeks,” while 24.4%

26 Gattig and Hendrickx
preferred this option when respective delays were 26 and 30 weeks). Similarly,
31% preferred a socially closer character (“Willem”) to receive the higher amount
of money, when both characters were close, but this figure dropped to 12.5% when
both characters were more distant from the decision maker. However, the size of
such effects is difficult to compare even within dimensions since they are strongly
dependent on the specific scenarios used. For instance, in research on temporally
delayed monetary outcomes, discount rates – that is, the percentual decrease in
value per year of delay—vary from 3–4% per year (which appears rational given
the usual market interest rates) to discount rates up to 345% per year (Frederick et
al., 2002; Loewenstein & Thaler, 1989; Thaler, 1981). The only effect that appears
to have a stable effect size is the sign effect in choice under uncertainty. Here,
a reoccurring finding is that people consider losses twice as important as gains
(Tversky & Kahneman, 1992).
A final behavioral regularity in choices under uncertainty and choices involving
temporal delay is the existence of framing effects. Kahneman and Tversky
(1984) and Loewenstein (1988) demonstrated that options are evaluated against a
reference point, for example current assets, which can be manipulated. Hence, the
perception of outcomes as gains or losses depends on the way choice problems are
formulated. Similarly, the perception of temporal delays can be framed as either
speed-ups or delays. Thus, variations in problem formulations that affect the decision
maker’s reference point may be used to make certain options more or less
attractive. For example, when a decision maker adopts a situation with the absence
of environmental risks as her or his reference point, (s)he will be more aversive
to accept new environmental risks than if the new risk is perceived as an increase
of an already existing risk. Similarly, when environmental risks are presented as
losses (e.g., “Our situation is not too good but acceptable; we may try to improve
things but then we run a risk of ending worse-off”) people will tend to avoid the
risk. If, on the other hand, environmental risks are presented as gains (e.g., “We
have a rather bad situation now, and this option might improve it. However, there
is a risk that we end worse than we are now”), people will be more inclined to
take or accept the risk. That is, environmental risks are more likely to be accepted
when they are presented as gains than when presented as losses. While established
firmly for decision making under risk and intertemporal choice, up to now such
framing effects have not been demonstrated for choices involving spatial or social
distance.
To sum up, there is evidence that humans discount outcomes that are uncertain,
temporally delayed, spatially distant, and/or occurring to others. The discounting
processes involved appear to be similar across different outcome dimensions.
Consequently, manipulations affecting discounting for one dimension similarly
affect discounting for other dimensions. For sustainability this result is potentially
problematic since many environmental risks involve several or even all of these
dimensions, which may result in severe discounting of the negative consequences.

Discounting and Environmental Risk Perception 27
In the following section, we will investigate whether discounting mechanisms are
also similar between decision domains.
Generalizability Across Different Decision Domains
Prior research on discounting has focused on several content areas or “decision
domains.” For instance, in studies on temporal discounting, financial choices
(Benzion, Rapoport, & Yagil, 1989; Stevenson, 1986), consumer decisions (Hausman,
1979; Loewenstein, 1988), medical and health issues (Cairns & Van der
Pol, 1997; Christensen-Szalanski, 1984), as well as environmental risks (Böhm &
Pfister, 2005; Hendrickx & Nicolaij, 2004) have been used to study how temporal
outcome-delay affects people’s judgments and choices. While in most studies one
particular decision domain was addressed, some explicitly compared discounting
in different domains. For instance, Chapman and Elstein (1995), Chapman
(1996a), and Chapman, Nelson, and Hier (1999) compared how people temporally
discounted medical versus financial outcomes in case of single future events.
The studies showed that while individuals apply a similar discount rate for different
decisions and judgments within a domain (e.g., future health states), the
discount rates people apply across different domains (e.g., money vs. health) are
essentially unrelated. The existence of domain differences was confirmed in studies
on people’s preferences for future outcome sequences. Chapman (1996b) and
Guyse, Keller, and Eppel (2002) compared people’s preferences for monetary,
health, and—in the latter study—environmental outcome sequences. Both studies
revealed clear domain differences. For instance, Guyse et al. (2002) found that
people prefer constant or improving outcome sequences for environmental quality
and for health, whereas for monetary outcomes most prefer a decreasing sequence.
Chapman (1996a) shows that the variability of discount rates across decision domains
is not caused by differences in how people evaluate money and health;
instead, domain differences appear to constitute a fundamental characteristic of
temporal discounting. Domain differences violate standard economic discount theory,
which prescribes that individuals should apply the same discount rate to all
types of goods and in all decision domains (see, e.g., Frederick et al., 2002).
Domain differences have also been demonstrated with regard to another preference
dimension. Research on how individuals deal with uncertainty—often operationalized
as a person’s “risk attitude” (Weber, Blais, & Betz, 2002)—has revealed
clear domain differences. For instance, Weber et al. (2002) studied people’s risktaking
tendency in six different decision areas (financial investments, gambling,
health and safety, recreational, ethical, and social decisions); they found that people’s
tendency to either seek or avoid risks is highly domain-dependent. Soane and
Chmiel (2005) compared risk preferences in three decision domains: work, health,
and personal finance. The risk-taking tendency of most respondents (85%) was
domain-specific and could not be generalized across domains. Similar to research

28 Gattig and Hendrickx
on time discounting (Chapman, 1996a), attempts have been made to ascribe domain
effects in risk attitudes to differences in the way people evaluate outcomes
in different domains, but the results were ambiguous. For instance, the idea that
domain differences would disappear, or at least diminish, by using an alternative
risk attitude measure, in which possible utility function differences are singled out
(the relative risk attitude, see Dyer & Sarin, 1982), was not empirically supported
(Keller, 1985; Krzysztofowicz, 1983).
In sum, it appears that domain differences occur for both preference dimensions
that have been studied extensively, that is, uncertainty and temporal delay.
Uncertainty and delay affect people’s decisions and judgments differently when
the decision at hand is about, say, a financial, a health, or an environmental issue.
Although the precise mechanisms underlying such domain differences are
not yet understood, it is clear that conclusions about how discounting affects
judgment and choice may not be generalized across different decision domains.
Therefore, to understand how discounting affects the evaluation of environmental
risks, we need to zoom in on discount studies that explicitly address environmental
issues.
Discounting of Environmental Risks
We will first focus on temporal distance, as this is the only preference dimension
that has been studied frequently in research on environmental risk evaluation.
Many environmental problems have long-term consequences. Some have both
immediate and long-term negative effects; for instance, urban air pollution from
traffic may cause immediate odor annoyance as well as long-term health problems
(see, e.g., Gärling & Schuitema, this issue). Other environmental problems, such
as the increase of atmospheric greenhouse gas concentrations or the depletion of
natural resources (e.g., oil, water, minerals), do not have severe immediate effects
but in the long run such risks may have catastrophic consequences. In such cases,
where it may take decades or centuries before the negative effects will occur, temporal
discounting can be expected to strongly affect people’s risk judgments and
their willingness to change relevant behaviors. Surprisingly, however, the results
from studies on temporal discounting of environmental risks point in a different
direction. Let us briefly review the available studies, which are summarized in
Table 1.
Svenson and Karlsson (1989) studied how people evaluate the long-term risks
associated to the storage of radioactive waste. Among other things, subjects were
asked to rate the seriousness of the consequences of a nuclear waste leakage, if
the leakage occurred at different moments in time (between the year 2100 and
2 million years into the future). While the mean seriousness judgments were
found to decrease with larger delays—which is consistent with standard discount
models— about 30% of the subjects did not discount at all. Apparently, for these

Discounting and Environmental Risk Perception 29
Table 1. Summary of Studies on Temporal Discounting of Environmental Risks
Study Risk(s) Studied
Reported Outcome
Delays (Range, Design) Main Finding
Svenson & Karlson Radioactive waste ∼110–2 million years ∼30% nondiscounters
(1989)
storage
within-Ss
Hendrickx et al. Soil pollution 5–90 years
∼40% nondiscounters
(1993)
within-Ss
Nicolaij & Hendrickx Greenhouse effect 5–100 years within-Ss ∼50% nondiscounters,
(2003)
and between-Ss no delay effect
Hendrickx & Nicolaij Soil pollution 1 month–25 years No delay effect
(2004)
Böhm & Pfister
(2005)
Water pollution
Coastal degradation
Water pollution
Between-Ss
1 month–10 years
Between-Ss
No delay effect
subjects the seriousness of consequences did not depend on when the leakage would
occur.
Hendrickx, Van den Berg, and Vlek (1993) studied how people discount delayed
negative effects of soil pollution. Subjects read 16 descriptions of different
cases of soil pollution, which were systematically varied on two factors: the temporal
delay and the likelihood of the negative consequences. The reported outcome
delay varied between 5 and 90 years. Subjects were asked to judge the riskiness of
each of these situations. Results were similar to the ones obtained by Svenson and
Karlsson (1989): on average, risk ratings decreased with longer outcome delays,
but analyses of individual data showed that around 40% of the subjects did not
discount at all.
Nicolaij and Hendrickx (2003) gave subjects information about the greenhouse
problem and varied the reported temporal delay of the possible negative
consequences of climate change (sea level rise, deterioration of vegetation and animals,
human health effects) across three conditions (5, 25, and 100 years). Among
other things, subjects were asked if their willingness to alter relevant behaviors
would change if the negative effects would occur sooner (e.g., if the delay was 5
instead of 25 years) or later (e.g., if the delay was 100 instead of 25 years). They
found that for almost 50% of the respondents, willingness to behave in environmentally
friendly ways does not depend on the temporal delay of the negative
consequences of global warming.
Thus, in the three studies in which outcome delay was varied as a withinsubjects
variable, a substantial percentage of people (30–50%) did not discount
delayed environmental outcomes. In Nicolaij and Hendrickx (2003), Hendrickx
and Nicolaij (2004), and Böhm and Pfister (2005), outcome delay was varied as a
between-subjects variable: subjects read short descriptions of various environmental
risks (global warming in Nicolaij & Hendrickx, 2003; soil and water pollution
in Hendrickx & Nicolaij, 2004; coastal degradation and water pollution in Böhm &
Pfister, 2005), in which the reported delay of the possible negative consequences
was systematically varied (delays between 1 month and 100 years). In all three

30 Gattig and Hendrickx
experiments, the outcome-delay manipulation failed to affect the main dependent
variables (risk judgments, emotions, behavior intentions). Evidently, the absence
of an experimental effect does not allow firm conclusions, but the complete lack
of delay effects in these studies is remarkable.
The substantial fraction of nondiscounters and the absence of experimental
delay effects may be typical for the environmental domain. In monetary discount
studies (for an overview, see, e.g., Frederick et al., 2002) individual discount rates
are seldom reported, but the high average annual discount rates usually found in
monetary studies (values up to 345% per year, see second section) suggest that
non-discounting is rare. Studies in the health domain also revealed high average
discount rates (Chapman, 2003, reports discount rates for the health domain up to
421% per year), but nondiscounting has also been observed in this domain. Van
der Pol and Cairns (2000) review discount studies in the health domain with a
methodology that allows establishing zero or negative discount rates (assessment
of individual rates, use of open-ended questions, or matching technique). In two
of the reviewed studies (Dolan & Gudex, 1995; Redelmeier & Heller, 1993) high
percentages of nondiscounting were observed (62% and 36% of the responses,
respectively). In the other reviewed studies, as well as in Van der Pol and Cairns’
(2000) own experiment, the nondiscounting percentages were much lower (or, in
some cases, not reported). So, in the health domain nondiscounting does occur,
but not systematically. Thus, the results from the studies in Table 1 indicate that
temporal nondiscounting is more prominent in the environmental domain than in
other domains.
Much less is known about whether the other three preference dimensions
distinguished above (uncertainty, spatial distance, and social distance) also result
in environmental risk discounting or whether the proportion of nondiscounting
respondents is equally high. To our knowledge, no research is available on how
the spatial or social distance of potential negative consequences of environmental
risks affects risk evaluations, although these dimensions seem particularly relevant
for global risks, such as climate change. For instance, if spatial discounting
does occur, then one would expect higher risk judgments from people living
at locations that are particularly vulnerable to the negative effects of climate
change, such as sea level rise or extreme weather events (e.g., hurricanes). International
comparisons in risk evaluations have been conducted (for a review, see, e.g.,
Boholm, 1998), but these studies did neither specifically address environmental
risks nor did they investigate the role of relevant location characteristics, such as
vulnerability.
In traditional formal risk models, uncertainty—defined there as: likelihood
of loss—often constitutes one of the model’s key terms; for gambling risks, likelihood
of loss was shown to be moderately strongly associated with risk judgments
(e.g., Slovic, 1967). Hendrickx et al. (1993) experimentally varied the
reported likelihood of the potential negative consequences of an environmental

Discounting and Environmental Risk Perception 31
risk (soil pollution) and found clear evidence for uncertainty discounting: mean
risk judgments were lower if the reported probability of negative outcomes was
lower. Psychometric and more qualitative studies of risk perception (reviewed in,
e.g., Boholm, 1998; Brun, 1994) revealed various factors that appear to influence
people’s risk judgments, several of which (e.g., novelty, ambiguity, disaster potential)
seem related to uncertainty. Unfortunately, these studies do not allow for
clear conclusions about the relative importance of uncertainty compared to other
factors found to affect risk judgments, such as familiarity, voluntariness of exposure,
perceived control, or outcome delay, nor about the possible interactions
among such factors. In the case of environmental risks, where outcomes tend to be
uncertain, delayed, as well as dependent on future actions (i.e., controllable), such
interactions may play an important role. For instance, studies by Gilovich, Kerr,
and Medvec (1993) and by Highhouse, Mohammed, and Hoffman (2002) suggest
that if a risk is (perceived as) controllable, outcome delay may evoke optimism
about the extent to which negative outcomes may be avoided and/or positive ones
be accomplished. However, no environmental risks were studied by Gilovich et al.
and by Highhouse et al., so additional research on how aspects like uncertainty,
delay, and perceived control interact and, in combination, affect environmental
risk perception seems worthwhile.
A Possible Explanation for Domain Differences
In our review of discounting mechanisms and their role in the evaluation of
environmental risks, we have seen that, on the one hand, discounting mechanisms
are stable across different preference dimensions. Regularities in judgment and
decision processes that have been observed with regard to one dimension, for
example uncertainty, also appear to apply to the other dimensions, such as temporal,
spatial, and social distance. On the other hand, the evidence discussed in the
previous two sections indicates that temporal discount rates and the way people
deal with uncertainty vary significantly across different decision domains. For
instance, temporal nondiscounting seems to occur more often for environmental
risks than for financial and health risks. Thus, while discounting mechanisms
appear to be robust across different preference dimensions, discount rates and
risk-taking tendencies are highly sensitive to a risk’s content domain. How can
this apparent contradiction be understood? A possible explanation arises once we
realize that there is more than one way in which people may comprehend and
evaluate risks. Recently, several “dual process” theories of risk evaluation have
been proposed (e.g., Böhm & Pfister, 2000; Loewenstein, Weber, Hsee, & Welch,
2001; Slovic, Finucane, Peters, & MacGregor, 2004), which we will discuss briefly.
Loewenstein et al. (2001) distinguish two fundamentally different psychological
mechanisms on which risk judgments, risky decisions, and behaviors are
based: one is a cognitive, ”consequentialist” evaluation strategy, which means that

32 Gattig and Hendrickx
risk judgments and risky decisions are based on subjective assessments of the
severity and likelihood of possible outcomes. The alternative, ”emotion-driven”
strategy entails that people’s reactions toward a risk are directly based on affective
responses to the risk, which include emotions like fear, worry, or anxiety. Since
emotional reactions toward a risk have other determinants than cognitive assessments
of risk, the two strategies can diverge; if that happens, the emotion-based
reactions will dominate people’s risk judgments, risky decisions, and behaviors.
Whether the affective reactions toward a risk will diverge from, and thus suppress,
the cognitive risk assessment depends on various situational factors, such as the
mental vividness of the potential outcomes and/or the temporal outcome delay (for
a detailed discussion, see Loewenstein et al., 2001). If such situational factors vary
systematically across different decision domains, then the prominence of the two
evaluation strategies will also differ per domain. For instance, if a typical health
or environmental risk evokes stronger emotions than a financial risk, for instance
because the possible negative outcomes are more vivid to people, then cognitive,
consequentialist evaluations will be less important in the former domains than in
the latter one, which could explain some of the observed domain differences in
discounting.
Slovic, Finucane, Peters, and MacGregor (2002, 2004) distinguish two similar
risk evaluation processes. In their terminology, people may assess risks both
“analytically” and “experientially.” In the first case, risk judgments are based on
formal, normative rules and algorithms (e.g., probability calculus), which requires
conscious, effortful, analytic mental activities. In the experiential system, on the
other hand, risk judgments are based on affect, emotions, and associative memories,
which are the result of fast, intuitive, and often largely unconscious mental
processes. Whereas Loewenstein et al. (2001) mainly focus on cases where the
two risk evaluation strategies diverge, Slovic et al. (2004) emphasize the complementary
role and the continuous interaction between the two modes of thought.
They argue that, for instance, affective responses may serve as cues to assess
key analytical elements such as loss probabilities. Slovic and colleagues highlight
the mutual dependency of the evaluation strategies, but they also provide some
evidence that the prominence of affect-based judgments depends on situational
factors, for instance on whether or not the risk judgments are made under time
pressure (Finucane, Alhakami, Slovic, & Johnson, 2000).
A third, somewhat different dual-process theory of risk evaluation was proposed
by Böhm and Pfister (2000, 2005). According to these authors, people’s
risk evaluations are based on two components: loss-related (or “consequentialist”)
and ethical concerns. Loss-related concerns refer to the possible negative consequences
of the risk at hand and comprise classical risk components such as the
probability and the seriousness of possible losses. Ethical concerns, on the other
hand, refer to the events or actions that caused the risk; if these actions or events
violate ethical principles or norms, the risk is considered as more serious. The

Discounting and Environmental Risk Perception 33
two evaluation strategies distinguished by Böhm and Pfister differ from the ones
in Loewenstein et al. (2001) and Slovic et al. (2004). While the latter authors
essentially differentiate between analytical and emotion-based risk judgment, the
evaluation strategies distinguished by Böhm and Pfister do not differ in the importance
of emotions, but in the nature of the emotions on which the risk judgment
is based: loss-related concerns may elicit emotions like fear or sadness, whereas
ethical concerns may give rise to emotions like anger or guilt (Böhm, 2003; Böhm
& Pfister, 2000, 2005).
Hendrickx and Nicolaij (2004) proposed an explanation for the relative prominence
of temporal nondiscounting in the evaluation of environmental risk (see
above), that was based on the Böhm & Pfister model. They argue that outcomedelay
is only relevant for loss-related concerns and not for ethical concerns, and
that, consequently, discount rates will depend on the relative importance of lossrelated
versus ethical concerns in the risk evaluation process. As shown by Böhm
and Pfister (2000, 2005) and by Hendrickx and Nicolaij (2004), the relative importance
of loss-related and ethical concerns depends—probably among other
factors—on the causal structure of a risk. Ethical concerns are more important
when the risk has a human instead of a natural cause and, if the cause is human,
when the people causing the risk and the potential victims are different (groups
of) people. Hendrickx and Nicolaij argue and provide evidence (see below) that
the causal structure of environmental risks differs from that of financial and health
risks. For instance, environmental risks are often caused by cumulative processes,
that is, they result from the actions of many people, whose individual contributions
are small. The potential negative consequences of such risks also affect many
people, but the people who cause the risk are not necessarily the ones who will
bear the (most severe) negative consequences. For instance, global warming is
mainly caused by economically well-developed countries as they contribute most
strongly to the greenhouse gas emissions, whereas the negative consequences of
global warming will probably be most severe in poor countries that lack the means
to take adequate protective measures. Most financial and health risks, on the other
hand, are personal risks, in which the person causing or taking the risk will also be
the main victim if things go wrong. Such differences in causal structure may evoke
differences in the importance of ethical concerns and, thus, in the prominence of
discounting.
To test these ideas, Hendrickx and Nicolaij (2004) asked subjects to rate
various real-world risks, environmental ones, and others, on several relevant characteristics.
Subjects also read short descriptions of realistic risks, in which both
the causal structure and the reported outcome delay were systematically varied.
Effects of these manipulations on, among other factors, risk judgments and the
prominence of ethical concerns were measured. The results confirm that environmental
risks differ in several regards from other risks. For instance, subjects rated
the consequences of environmental risk as more delayed than those of other risks.

34 Gattig and Hendrickx
Subjects also considered situations in which the potential victims of a risk are not
the people who caused the risk as more typical for environmental than for other
risks. And, thirdly, ethical concerns were more prominent for environmental risks
than for other types of risk. Thus, the notion that environmental risks differ from,
for example, health and financial risks was confirmed, but whether these differences
can explain the prominence of nondiscounting could not be established in
this study.
Summary
Summary, Research Suggestions, and Policy Implications
In this article, we reviewed empirical results from behavioral decision research
in areas relevant to environmental risk perception and decision making. We
highlighted the similarities in the processes underlying uncertainty discounting,
temporal discounting, spatial discounting, and social discounting. We then drew
attention to the fact that discounting seems fairly sensitive to a risk’s content domain
(e.g., financial vs. health vs. environmental risks). For instance, with regard
to temporal discounting, environmental risks appear to differ from other types of
risk in that a substantial fraction of people (30–50%) does not discount at all. Dualprocess
risk theories may offer insight in the causes of such domain differences. A
common finding in research on dual-process theories is that the way people react
to a risk depends on specific risk characteristics, such as the causal structure of the
risk or the vividness of the possible consequences. If risks from various decisions
domains differ with respect to such factors, then the prominence of different risk
evaluation strategies may vary systematically across different domains. In other
words, domain differences in the way people deal with a risk may simply reflect
(average) differences on the factors that determine the prominence of different risk
evaluation strategies.
Future Research
Identification of different risk evaluation strategies and, especially, of the
factors that encourage or discourage the use of specific risk evaluation strategies
should have high priority on the risk research agenda. In addition, we should establish
if (and how) risks from various domains differ on such factors. Hence, we need
to study how—in the eyes of the people whose reactions and behaviors we want
to understand, predict, or change—specific risks score on the key determinants of
risk evaluation strategies. In part, that information may be derived from studies
in the psychometric research tradition, where subjects were asked to rate numerous
risks on various risk characteristics. Unfortunately, the factors that affect the
prominence of different risk evaluation strategies (e.g., causal structure, outcome

Discounting and Environmental Risk Perception 35
vividness, outcome delay, time pressure; see previous section) did receive little
attention in these studies, so additional research on how people perceive specific
risks in terms of the key determinants of risk evaluation strategies is necessary. Obviously,
different risks within a particular domain may also differ on such factors
and thus evoke different evaluation strategies. For instance, environmental risks
with a natural cause (e.g., air pollution due to volcanic activity) may be evaluated
differently than a similar risk with a human cause (e.g., air pollution from motorized
traffic). For other examples, see Brown, Peterson, Brodersen, Ford, and Bell
(2005). Thus, categorization of risks in terms of the fundamental determinants of
how people evaluate a risk, such as its causal structure, may help us understand
both differences between decision domains, as well as differences between risks
within one domain.
In addition, future research should investigate decision making when more
than one dimension is involved. Scarce examples of such research are Stevenson
(1992), Keren and Roelofsma (1995), Ahlbrecht and Weber (1997), and Weber
and Chapman (2005). This research suggests that combined discounting (i.e., discounting
when several preference dimensions are involved) is less strong than
what one would expect from simply aggregating the respective discounts alone.
For example, if a reward of $100 with a probability of .95 is worth $95 for sure to
the decision maker and if the same reward delayed by 4 weeks is also worth $95
now, then a reward with a probability of .95 in 4 weeks will be judged as being
worth more than multiplying the discount rates for each dimension would suggest. 4
Hence, adding temporal delay to an already uncertain reward is less “harmful” than
adding the same delay to a certain reward. However, research on adding preference
dimensions other than uncertainty and temporal delay is completely lacking.
Thus, it remains unclear whether the phenomenon that combined discounting
tends to be less strong than one would expect on the basis of normative decision
theory, is restricted to combinations of temporal and uncertainty, or whether
this effect will also occur if other dimensions are added. The latter result would
corroborate the reasoning above, but further studies addressing this question are
necessary.
Together with the results reported in this article, such insights would contribute
to our understanding of the way in which people perceive, evaluate, and handle
environmental risks and, as will be discussed below, thereby enhance the chances
for achieving environmental sustainability.
Policy Implications
Promoting sustainability often requires behavioral changes. Such changes can
either be achieved voluntarily, for example through appeals, or by coercion. Our
4 According to normative decision theory, the two discount rates should be multiplied.

36 Gattig and Hendrickx
study’s main policy implication is that environmental decision making appears to
be more long-term oriented than decisions in other domains. Contrary to decision
making in other domains, when environmental risks are at stake a substantial
fraction of people seems to take future considerations fully into account. Thus, appealing
to the public’s long-term preferences may be more efficient in the case of
environmental risks than for, for example, financial risks. This long-term orientation
potentially could be enhanced by the use of appropriate problem descriptions,
for instance, by presenting future outcomes as potential losses against the status
quo (see also Midden, Kaiser, & McCalley, this issue). The research discussed also
suggests that people weigh uncertain, delayed, or distant outcomes more heavily
(i.e., discount less) if they are caused by humans and if the negative consequences
are not borne by (or limited to) the people who caused the risk. Hence, by emphasizing
human responsibilities in the causation of the risk, or by highlighting
discrepancies between cause and victims, one may increase the prominence of
ethical concerns (or in the terminology of Lindenberg & Steg, this issue: of the
normative goal-frame) in people’s risk evaluations. This in turn may result in
behaviors or decisions that are (more) in line with environmental sustainability.
Designers of behavior modification and/or risk communication programs could
(and should) make use of these insights.
Another implication of the findings reported above is that policies based on
standard economic theories may not match the preferences of a significant proportion
of the population. In the past decades, an increasing number of economists
engaged in environmental and resource economics, thereby providing highly valuable
insights with respect to sustainability. However, standard economic theories
still postulate that future outcomes should be discounted at a rate that is constant
over time—or at least across the entire period the outcome is to be delayed—and
that lies in the range of the current market interest rate (see Loewenstein & Thaler,
1989). As a consequence, future events that are delayed for several decades or
more will lose almost all significance. Given the very long time span, for instance,
in the case of nuclear waste, throughout which environmental risks prevail, this
procedure may result in an almost complete neglect of the needs of future generations.
This is in conflict with environmental sustainability as well as with the
preferences of a large part of the public.
In addition, for a substantial part of the population standard economic thinking
may lead to counterintuitive recommendations with regard to policy decisions
about how to deal with scarce natural resources. For instance, it is in accordance
with standard economic thinking to completely exhaust a natural resource if the
gains obtained from it can be invested at a return rate that is higher than the
respective discount rate, that is, the market interest rate. Given the prominence of
nondiscounting observed in environmental risk discounting, policies solely based
on economic theories thus may arrive at solutions that are incompatible with the
preferences of a considerable fraction of the population.

Discounting and Environmental Risk Perception 37
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ALEXANDER GATTIG studied sociology and economics at the University of
Bremen, Germany, specializing in applied game theory and event history analysis.
He obtained his PhD at the University of Groningen, the Netherlands. His dissertation
thesis centered on intertemporal choices, especially the cognitive mechanisms
underlying discounting processes in choice under risk and intertemporal choice.
Currently, he works as a postdoc at the University of Bremen, Germany. His project
focuses on international comparisons of trends in voting behavior and social mobility.
In the past he spent some time at Nuffield College, Oxford, and Stanford,
USA. His research interests include behavioral decision theory and categorical
data analysis.
LAURIE HENDRICKX obtained his PhD at the University of Groningen, based
on research about the cognitive processes underlying people’s risk judgments and
risky decisions. Currently, he is assistant professor at the Center for Energy and Environmental
Studies (IVEM) at the University of Groningen. His research interests
focus on the psychological mechanisms underlying environmental risk perception
and environmentally relevant behaviors. He has conducted and/or supervised several
research projects about the role of temporal factors in risk evaluation and
social dilemmas. More applied research projects were aimed at understanding,
predicting, and/or changing environmentally relevant behaviors, in domains such
as mobility and household energy use.