Optimistic bias in relation to preparedness for earthquakes

Matthew J. Spittal, Victoria University of Wellington, Wellington, New Zealand
John McClure, School of Psychology, Victoria University of Wellington, PO Box 600, Wellington, New Zealand. Email address: john.mcclure@vuw.ac.nz
Richard J. Siegert, University of Otago, Wellington School of Medicine
Frank H. Walkey, Victoria University of Wellington, Wellington, New Zealand

Matthew J. Spittal

Victoria University of Wellington,
Wellington,
New Zealand

John McClure

Victoria University of Wellington,
Wellington,
New Zealand

Richard J. Siegert

University of Otago,
Wellington School of Medicine
Wellington
New Zealand

Frank H. Walkey

Victoria University of Wellington,
Wellington,
New Zealand

Optimistic bias in relation to preparedness for earthquakes

The devastating damage caused by natural disasters such as earthquakes can be reduced by appropriate preparation (e.g., Ansell & Taber, 1996; Kreps, 1984; McClure & Williams, 1996; Sorenson & Mileti, 1987). When no preparation is undertaken, the losses can be catastrophic (Norris, 1992), whereas when citizens take steps to prepare for natural disasters, the losses may be substantially reduced.

Although government actions and legislated building standards can reduce vulnerability, individuals also need to act to limit damage. Individuals can prepare for a natural disaster by ensuring that their homes meet or exceed the relevant building standards and that they have provisions for survival after a disaster. Individuals can also choose to live in safer buildings and in safer geographical locations.

Despite the demonstrated value of preparedness, a common finding in research on natural disasters is citizens’ lack of preparation for such events (e.g., Edwards, 1993; Farley, Barlow, Finklestein, & Riley, 1993; Kunreuther, 1974; McClure, Walkey, & Allen, 1999; McClure & Williams, 1996; Mileti & Sorenson, 1987; Paton, Millar, & Johnson, 2001; Rustemli & Karanci 1999; Sattler, Kaiser, & Hittner, 2000; Sorenson & Mileti, 1987; Weinstein, 1987a). In relation to earthquakes, Jackson and Mukerjee (1974) found that only a small percentage of their respondents had made any structural changes to their homes or purchased insurance. Turner, Nigg, and Paz (1986) found that many California residents lacked first aid supplies for an earthquake. Rustemli and Karanci (1999) similarly found that vulnerable citizens in Turkey had adopted few precautions for an earthquake.

Researchers have examined the judgmental processes that facilitate and hinder preparation (Lindell & Perry, 2000). Research has shown the role of efficacy factors such as fatalism (e.g., Turner et al., 1986), locus of control (e.g., McClure, Walkey, & Allen, 1999; Schiff, 1977), person-relative-to-event factors (e.g., Duval, & Mulilis, 1999), and attributions for earthquake damage (McClure, Allen, & Walkey, 2001). A second focus of research has included risk judgments (e.g., Lindell & Whitney, 2000; Slovic, Kunreuther, & White, 1974; Slovic, 1987) and risk-taking propensity (e.g., McClure, Walkey, & Allen, 1999; Schiff, 1977).

Risk judgment and Optimistic bias

A key issue in the research on risk concerns the issue of optimistic bias, a pattern of judgments where people see themselves as less likely to be harmed by future risks than others (e.g., Helweg-Larsen, 1999). Research has shown that people often make biased appraisals of their own risks and prospects relative to other persons. When individuals predict their own and other persons’ prospects, they often judge that they are more likely to have a happy future and less likely to have poor health (Weinstein, 1980; 1984; 1987b). People who show this bias underestimate the likelihood that they will experience a negative event (Weinstein & Klein, 1996). They also judge that they engage in risky behaviour less often than their peers, and that they adopt precautionary behaviours more often than their peers (Perloff & Fetzer, 1986). This optimistic bias has been demonstrated in relation to a wide range of risky activities, including motorcycle use (Rutter, Quine, & Albery, 1998), bungy jumping (Middleton, Harris, & Surman, 1996), and vulnerability to health risks such as radon (Weinstein, Sandman, & Roberts, 1990).

The optimistic bias has been linked to people’s experience of natural disasters, and has important implications for preparedness. Burger and Palmer (1992) examined optimistic bias in people who had recently experienced a major earthquake. Students rated the likelihood that they would experience each of nine negative life events, one of which was being ‘seriously hurt in a natural disaster (flood, earthquake, storm)’. At Time 1, three days following the earthquake, optimistic bias was reduced, but three months later, optimistic bias returned.

Helweg-Larsen (1999) questioned this finding that optimistic bias re-emerges some time after personal experience of a disaster. Following the 1994 earthquake in Northridge, California, she examined judgments over a five-month period of the likelihood of injury stemming from an earthquake, and nine other negative life events. Optimistic bias was seen in relation to judgments about the other negative events, but not with judgments of risk of injury from earthquakes. (See also Weinstein, Lyon, Rothman, & Cuite, 2000). Helweg-Larsen attributed the difference between her own findings and those obtained by Burger and Palmer to the fact that whereas Burger and Palmer used a broad question about natural disasters, her own measure asked participants specifically about earthquakes. Her findings suggest that personal experience of an earthquake may have long-term affects in reducing optimistic bias.

In studies of optimistic bias, participants judge the likelihood that both they and members of their peer group will experience the same event (Helweg-Larsen & Shepperd, 2001). Other studies have examined optimism solely concerning the citizen’s own prospects in a disaster. Jackson (1981) found that a majority of participants in regions prone to earthquakes believed either that they would not experience an earthquake or that if an earthquake did occur, they would not experience personal damage. Lehman and Taylor (1987) showed that students who lived in dormitory buildings with poor seismic resistance tended to play down the seriousness of the earthquake risk. Sattler et al. (2000) found that most participants believed that an impending hurricane would strike and cause significant damage to their homes, but most believed that the building they lived in could withstand a hurricane. Similarly, Mileti and Fitzpatrick (1993) found that although 80 percent of their participants believed that they would experience a major earthquake, most thought it would not harm them or their property.

These studies suggest that people display optimism in relation to disasters, but they measured participants’ optimism only with regard to their own prospects. Because comparative judgments between one’s own prospects and other people’s prospects provide a more complete measure of optimistic bias, the present study used this comparative measure to investigate whether people show optimistic bias with regard to an earthquake that is highly probable, but has not occurred in recent times in their immediate locality. In this locality (Wellington, New Zealand), the last major earthquake happened 150 years previously (1855), a time when there was only a small human settlement. Thus few if any of the citizens would have experienced a major earthquake, and therefore their personal experience would not be expected to reduce optimistic bias (cf. Helweg-Larsen, 1999). We assessed participants’ optimistic bias in relation to three criteria: preparedness, personal loss, and property damage.

Other researchers studying optimistic bias have pointed out that the frequently used comparison target ‘the average other person’ differs from the self in several respects other than the person being identified (Alicke, Klotz, Breitenbecher, Yurak, & Vredenburg, 1995; Klar & Giladi, 1997). The concept of the ‘average other person’ is more abstract than the notion of one’s self, and deals with a generalized other rather than a particular other. These researchers suggest that it is more appropriate to compare judgments about the self with judgments about a specific acquaintance who is not a close friend, to avoid issues of identification. In response to these proposals, the present study included two versions of the comparison target. The first question dealing with a comparison target measured judgments about the vulnerability of a specific acquaintance (as suggested by Klar & Giladi), whereas the second question was a more general question as used in many previous studies, referring to “most people who live in Wellington” (the participants’ home city).

Research Overview

The aim of the study was to investigate whether participants demonstrated optimistic bias with regard to a major earthquake, using enhanced measures of the bias. Judgments were examined for three targets: self, an acquaintance and the average other person in Wellington. Judgments were made on three criteria: level of preparation, the likelihood of harm, and the likelihood of damage to property. We predicted that participants would judge that they were more prepared for an earthquake than both comparison targets, and that they were less likely to suffer harm and property damage than either comparison target.

Method

To collect data that are representative of the whole population, the New Zealand national statistics agency, Statistics New Zealand, partitions New Zealand into geographic entities called area units. In the present study, the 63 area units that comprise Wellington City provided the basis for sampling participants. Using the 1996 Census data, the average household income for each area unit was calculated and used as the basis for segmenting the area units into five evenly sized groups. The two area units with the largest population from each of these groups were selected, producing ten sampling units.

Measures

Earthquake preparation was assessed using the Earthquake Readiness Scale (ERS) (Spittal, Walkey, McClure, & Siegert, 2005). This 23-item scale assesses the number of steps that people have taken to prepare for a major earthquake (e.g., stored water, fastened tall furniture to the wall, strengthened chimney, etc). The instructions asked participants to indicate, by circling Yes or No, the steps they had taken to prepare for a major earthquake, including steps taken to mitigate the impact of an earthquake, and steps taken to increase the probability of survival when one has occurred. An example of the mitigation items is “I have either strengthened my house to increase its earthquake resistance, or satisfied my self that it will probably not fall down in a major earthquake”. An example of the survival items is “ I have stored water for survival”. Two independent confirmatory factor analysis procedures using four parcels of items (Kishton & Widaman, 1994) indicate that the items form a unidimensional scale. For the larger of these samples, the fit to the model was good, X² (2) = 5.77, ns, GFI = .99, and there were low levels of error, RMSEA = 0.00. The scale had an alpha reliability of .85 (Spittal et al., 2005).

Optimistic bias was measured by two sets of questions. The first set obtained judgments of the perceived level of preparation for a major earthquake by self and others: (1) “How prepared do you think you are for a major earthquake?” (2) “Think of an acquaintance (someone you know only slightly) who lives in the Wellington region. How prepared do you think they are for a major earthquake?” (3) “How prepared do you think most people who live in the Wellington region are for a major earthquake?” A seven-point Likert scale had anchor points labelled not prepared and very well prepared.

The second set of questions assessed judgments about injury and damage to the property of self and others: “If a major earthquake were to occur in the Wellington region, how likely do you think it is that it would cause: (1) harm to you? (2) damage to your property? (3) harm to the person you thought of when answering Question 2 [the acquaintance in the first set of questions]? (4) damage to the property of the person you thought of when answering Question 2? (5) harm to most people who live in Wellington? (6) damage to the property of most people who live in Wellington?”. A seven point Likert scale had anchor points labelled very unlikely and very likely.

Demographic questions obtained participants’ gender; ethnicity; age (banded estimates: 15 to 24, 25 to 44, 45 to 64, 65 and over); marital status (single, long term relationship, married, divorced, other); number of dependent children; highest educational qualification (no formal qualification, secondary school qualification, university/polytechnic degree or diploma); whether they owned their own home; and length of residence at their current address (less than a year, between 1 and 10 years, more than 10 years). The demographic data are reported in some detail in Spittal, McClure, Siegert, and Walkey (2004).

Procedure

A total of 1,000 questionnaire booklets were delivered to households across the sampling units. A starting point was randomly selected in each of the ten area sampling units that comprise the sampling zones for the study, and questionnaires were delivered to every second residence until 50 had been distributed. A stamped envelope was provided for participants to return their responses. Due to ethical considerations, the survey was conducted in an anonymous manner and call-back procedures were not employed. The response rate for this survey was 36 percent.

Results

Seven of the 358 questionnaires had incomplete data, but the questionnaires were included in the analysis. The small differences in the degrees of freedom in the following analyses reflect the inclusion of these data. The mean total score for the Earthquake Readiness Scale (ERS) was 10.7 (SD = 5.0) out of a possible 23, with higher scores indicating greater preparation.

Optimistic bias in Earthquake Judgments

Table 1 shows participants’ judgments of their own preparedness and the likelihood of a major earthquake causing harm to themselves, to an acquaintance, and to other Wellingtonians, and the parallel judgments about damage to property. Higher values indicate a greater likelihood.

Table 1. Judgments of preparedness and likelihood of harm and damage to self,
an acquaintance and other Wellingtonians

	Preparedness	Harm	Damage to Property
Self	3.29 (1.50)	4.29 (1.59)	5.38 (1.43)
Acquaintance	2.71 (1.28)	4.42 (1.57)	4.20 (1.50)
Wellingtonians	2.72 (1.00)	4.33 (1.64)	5.18 (1.41)

A one-way analysis of variance was performed on the judgments of preparedness i.e., how prepared individuals believe they are for a major earthquake and how prepared they believe an acquaintance is or other Wellingtonians are. As predicted, participants judged that preparedness was significantly higher for the self (M = 3.29) than for an acquaintance (M = 2.71), or for other Wellingtonians (M = 2.72), F(2, 696) = 38.54, p<.001.

A 3 X 2 within subjects ANOVA (target: self, acquaintance, other Wellingtonians X harm type: self, property) examined differences between the three comparison targets and the two harm types. This analysis showed no main effect for target, F(2, 700) = 1.23, ns, but a significant main effect for harm type, F(1, 350) = 208.96, p < .001, indicating that participants thought it much more likely that the relevant homes would suffer damage than that the owners would be harmed. There was also a significant interaction between target and harm type, F(2, 700) = 13.41, p < .001. A one-tailed paired sample t-test showed that, as predicted, participants anticipated less harm to the self than to an acquaintance, t(353) = 2.35, p < .01, but counter to our prediction, they anticipated more damage to their own property than to that of an acquaintance, t(352) = 3.65, p < .01.

Table 2. Correlation matrix: Earthquake preparation and optimistic biases

	1	2	3	4
1 Earthquake Preparation	-
2 Preparation bias	.34^*	-
3 Harm/injury bias	-.05	-.08	-
4 Property damage bias	-.06	-.19^*	.37^*	-

A further analysis examined whether optimistic bias predicted scores on the preparation scale. Optimistic bias was calculated from the self and acquaintance judgments in each of the three domains, i.e. one’s own preparation minus the acquaintance’s preparation; one’s own likelihood of harm minus the acquaintance’s likelihood of harm; one’s own likelihood of damage to property minus the acquaintance’s likelihood of damage to property. The resulting three scores were correlated with preparedness (see Table 2). A regression analysis was performed which showed that optimism about one’s own preparation relative to others predicted actual preparedness, whereas the other two measures were not significant predictors (Table 3).

Table 3. Multiple regression analysis for optimistic biases prediction earthquake preparation

Variable	B	SE B	B
Intercept	10.65	0.27
Preparation bias	1.06	0.16	.34*
Harm/injury bias	-0.13	0.23	.06
Property damage bias	0.08	0.29	.08

Discussion

A central goal of the present study was to examine systematically whether citizens in a known earthquake risk zone show an optimistic bias with respect to a future earthquake. As predicted, participants judge themselves to be more prepared for a major earthquake than either an acquaintance or other Wellington residents. The results partially support the prediction that participants would judge that they were less likely to suffer harm than an acquaintance or other Wellingtonians. Participants judged their own chances of being injured in a major earthquake as less than those of an acquaintance; however, there was no difference between their predictions of harm to themselves and harm to other Wellingtonians. These findings are generally consistent with those of previous research on optimistic bias in relation to negative life events (e.g., Perloff & Fetzer, 1986; Weinstein, 1980; Weinstein & Klein, 1996).

These findings also extend research on expectancies about harm to property, which in the past has focused on damage to participants’ own property (Mileti & Fitzpatrick, 1993; Sattler et al., 2000). The present research expanded on these studies by examining participants’ predictions about their own and other people’s property. One unexpected outcome was the lack of support for the prediction that participants would judge that their own property was less likely to suffer damage in an earthquake than the property of an acquaintance, or that of other Wellingtonians in general. In contrast, participants judged that there was a greater likelihood of their own property being damaged than the property of an acquaintance or of other Wellingtonians.

Explanations for this finding are speculative in nature. One possibility is that people may be more aware that their own home lacks earthquake resilience, but this seems unlikely because people usually select a more risky target to compare themselves with (Perloff & Fetzer,1986). It is possible that the fear of financial loss is less susceptible to optimistic bias. The value that people place on their own homes may be greater than that placed on the property of others, and people may see themselves as owning an above average property. The findings on the harm and damage ratings may reflect the wording used for the average other person measures: “harm to most people who live in Wellington” and “damage to the property of most people who live in Wellington”. This wording may have been interpreted by some participants to mean a majority of the population of Wellington, rather than an abstract generalized other. Such an outcome would require a massive earthquake. This ambiguity could explain the lack of a difference between self and other Wellingtonians on the harm and damage ratings, which contrasts with the clear differences on the self versus acquaintance measures. Further research may clarify this issue.

The analysis examining optimistic bias as a predictor of preparedness shows that people who judge they are better prepared than an acquaintance are actually more prepared for an earthquake than others. This result is interesting, because it suggests that the ratings are not purely a reflection of bias, but an accurate assessment of the participants’ levels of preparedness. Many studies of optimistic bias lack other measures by which to assess whether the judgments might have some accuracy. In contrast, the present study provides a criterion measure of actual preparedness against which perceptions of preparedness can be compared. The results show that judgments that are labelled as a bias in the absence of such a criterion measure may represent an accurate judgment. However, this relationship between optimistic bias and actual preparedness, although significant, is modest, though this may be partly a function of the attenuation in variance resulting from the use of difference scores to calculate optimistic bias. This finding suggests that personal levels of preparedness account for only some of the higher ratings observed in judgments of own preparedness compared with the preparedness of others. In other words, even though participants who thought they were better prepared than others actually were better prepared, participants did overestimate their own preparedness relative to others.

Conclusion

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Matthew J. Spittal, John McClure, Richard J. Siegert & Frank H. Walkey © 2005. The authors assign to the Australasian Journal of Disaster and Trauma Studies at Massey University a non-exclusive licence to use this document for personal use and in courses of instruction provided that the article is used in full and this copyright statement is reproduced. The authors also grant a non-exclusive licence to Massey University to publish this document in full on the World Wide Web and for the document to be published on mirrors on the World Wide Web. Any other usage is prohibited without the express permission of the authors.