The consequences of many of life’s decisions are plagued by uncertainty, so each decision must incorporate an assessment of the “desirability of possible outcomes and their likelihood of occurrence” (Tversky & Fox, 1995, p. 269). The more we assess these two attributes (possible outcome and probability of occurrence) when we make the same uncertain choices, the better we may become at judging the consequences and we should therefore make better decisions. However, where uncertainty is present rational decision-making is not always a given (Basili, 2006; Donovan & Blake, 1992; Jones, 1999; Slovic, Finucane, Peters, & MacGregor, 2004).
People often do not reach rational decisions as a result of their cognitive reasoning – partly because of the social construction of risk, and partly because active cognition is undertaken with the information at hand, and often with deduction aimed not at reaching a rational outcome, but to reach the most agreeable outcome (Finucane, Alhakami, Slovic, & Johnson, 2000; Loewenstein, Hsee, Weber, & Welch, 2001; Tversky & Kahneman, 1974, 1981). It is quite clear that an individual’s judgement can be biased by their beliefs, attitudes, feelings and emotions at the time the decision is made (I liked the car’s colour and forgot to look under the bonnet), leading to illogical choice (Bechara, Damasio, Tranel, & Damasio, 1997; Donovan & Blake, 1992; Jones, 1999; Kahneman, 2003; Simon, 1955). Tversky and Kahneman (1974) showed that individuals rely heavily on affect heuristics to guide their judgement, enabling them to simplify otherwise difficult choices. But once the choice is simplified in this way, judgemental errors are likely to become more common (Finucane, et al., 2000; Jones, 1999; Kahneman, 2003; Sjöberg, 1982; Slovic, et al., 2004; Tversky & Kahneman, 1974). This plays a role even in choices familiar to the decision maker (Tversky & Kahneman, 1974), but in familiar circumstances individuals are likely to be able to better judge the possible outcomes and estimate how likely these are to occur, giving them some ability to choose advantageously to avert risk (Bechara, et al., 1997; Finucane, et al., 2000; Fox & Levav, 2000; Kahneman, 2003; Keller, et al., 2006; Sjöberg, 1982).
On the other hand, natural hazards are rare, unpredictable, and pose unfamiliar risks (Emdad Haque, 2000; McCaffrey, 2004b; Mileti & Fitzpatrick, 1992; Ripley, 2006; Slovic, 1987). Under such ambiguity our choices can’t be informed by familiarity because we have no experience, we often can’t conceive of the effects of such threats, and it’s difficult to respond to them given we have little knowledge about how or when to do so (Basili, 2006; Basili, Chateauneuf, & Fontini, 2005). In these circumstances uncertainty and unfamiliarity contribute to the hazardous nature of the circumstances in which people find themselves. What confounds our decision-making further is the fact that the consequences we face, if we have made poor judgements or have not processed the available information adequately when a natural hazard actually occurs, can be life threatening.
Tversky and Kahneman (1974) showed that people assess the probability of uncertain events using several judgemental heuristics. Although the heuristics of representativeness
(judgements are based on similarities with known elements), availability (frequency by which events can be recalled) and anchoring (judgements about an event are determined based on perceived starting points) provide workable mechanisms by which individuals formulate ideas about uncertain events, they mostly result in judgemental errors. Whether people employ such heuristic principles to educate their conceptualisations of risk and probability is not a function of their desire to understand uncertain events, but simply to compensate for the little knowledge they possess about these events, whose effects might be clarified if they can develop some idea as to why or how they might operate.
Therefore, uncertainty is essentially a state of “not knowing” (Kahneman & Tversky, 1982; Powell, et al., 2007; Tversky & Kahneman, 1974). Members of the public are generally limited by their own knowledge, the knowledge of others, the knowledge that exists around them, an inability to find out (and having to rely on second-hand information) or a combination of these. Under these circumstances we attribute probabilistic judgements (Fischhoff, et al., 1982; Siegrist, 1997; Tversky & Kahneman, 1973) to risks in order to legitimise our “not knowing” by asserting that although unpredictable, a risk is nevertheless possible within some future time frame. Risk communicators have often resorted to communicating probabilities in order to engender responses to environmental risk, yet these techniques are now shown to be next to useless (Siegrist, 1997) partly because they perpetuate these states of “not knowing”.
Distressingly, even when we don’t know, we must still make decisions about natural hazards. The fundamental uncertainty of natural hazards has dramatic influences on whether we actually choose to undertake those protective behaviours communicated to us by risk management agencies (Nisbett & Ross, 1980; Powell, et al., 2007; Tversky & Fox, 1995; Tversky & Kahneman, 1992). If we believe that the chance of a hazard occurring is minimal, then we are unlikely to consider mitigating the risk from that hazard as important – particularly when there are many other pressures in our lives that require more immediate attention (Fox & Irwin, 1998; Hill & Thompson, 2006; Weinstein, 1989). Laypeople use information acquired from multiple sources (first-hand experience, media, interpersonal relationships) to construct their ideas of risk and hazard likelihood (Powell, et al., 2007). What they know, but also what they don’t know can affect the way they interpret environmental risk information, their perceptions of that risk, whether they feel they require more information about the risk, and
whether they should act to mitigate the effects of that risk. So the uncertainty of natural hazards plays a key role in determining how we respond to the threat such risks pose.