have a finite pool of worry (Weber, 2006). As concern about one type of risk increases, worry about other risks frequently decreases, as if people had a limited budget to spend on worry. A Pew (2009) opinion poll found that levels of concern about climate change had declined in October 2009 relative to a high in 2006 that was still maintained in May of 2008. Presumably this recent decline in climate change concern is the result of recent increases in concern about the national and world economy and unemployment. Hansen, Marx and Weber (2004) found evidence consistent with a finite pool of worry among farmers in the Argentine Pampas. As concern about climate risk increased in the course of a two-day farm decision workshop that provided information about the potential impacts of increased climate variability, concern about political risk went down (post- vs. pre-workshop) even though the level of political risk had not changed over those two days. In addition, those who stated greater worry about political risk (either pre- or post-workshop) worried less about climate risk. If people’s capacity for worry or concern is finite, then efforts to raise greater concern to motivate protective or mitigation action against some risk by, for example, providing concrete images of possible damages, comes at the cost of potentially reducing concern about other risks. The finite pool of worry concept is related to, though certainly not identical to the concept of risk homeostasis (Wilde, 1998).

Fear appeals are also problematic because of the single-action bias (Weber, 1997), which refers to the propensity to take only a single action in response to a fear signal, even in situations where a broader set of remedies might be called for. Taking the first action to respond to a problem at hand seems to reduce or remove the feeling of worry or concern. Without this affective marker, motivation for further action is reduced. Weber (1997) found that Midwestern farmers engaged in only one of three plausible classes of protective actions against climate change. Hansen, Marx and Weber (2004) similarly found that farmers in Argentina employed only one of several protections against climate variability and climate change. If they had the capacity to store grain, for example, they were less likely to also irrigate and invest in crop insurance. Thus fear appeals may also backfire because they motivate people to take simpler actions than warranted by the complexity of contemporary problems.

# **Rule- and role-based decisions**

In recognition-based decision-making, the decision-maker recognises a decision situation as a member of a class for which a satisfactory action is known (Simon, 1990). Recognition-based decisions come in different variants. In case-based decisions, the decision-maker is typically an expert with a memory store full of specific situations in her domain of expertise, with the most appropriate action stored for each one. These mental representations can be thought of as “if-then” productions, where the “if” element is a set of conditions that must be met in order to trigger the resultant action represented by the “then” part of the production. The expert decision-maker is able to unconsciously apply these production rules, which 23