Optimism bias, originally referred to as unrealistic optimism (Weinstein, 1980), is the tendency of individuals to underestimate the likelihood they will experience adverse events, such as skin cancer or car accidents. As a consequence of this bias, some individuals might disregard precautions that might curb these risks. They might not, for example, wear seatbelts.
Research has uncovered several factors that amplify or inhibit the probability that individuals will underestimate some risk. When individuals feel anxious or unconfident, for instance, optimism bias tends to diminish.
Optimism bias has been uncovered in a vast range of settings. For example, smokers tend to feel they are less likely than other individuals who smoke to be afflicted with lung cancer (Windschitl, 2002;; also see Weinstein, Slovic, Gibson, & Waters, 2004). Motorists tend to feel they are less likely to be involved in a car accident than is the average driver (Dalziel & Job, 1997). Students tend to overestimate their capacity to pay debts relative to their peers (Seaward & Kemp, 2000). Individuals tend to feel they are less vulnerable to environmental degradation and problems, such as air pollution, than peers (Hatfield & Job, 2000).
Two main approaches are applied to assess optimism bias. First, in some studies, participants are explicitly instructed to rate the likelihood they will experience some adverse event, such as a snake bite, relative to other individuals-usually on scales ranging from "much less likely" to "much more likely". This procedure, called the direct approach, tends to demonstrate that participants feel they are less likely, on average, to experience adverse events than are other individuals.
Second, in some studies, participants are instructed to estimate the likelihood they might experience some adverse event. In a separate question, they are asked to estimate the likelihood that other individuals might experience some adverse event. The difference between these two estimates is then calculated, called the indirect method.
Recent studies show the direct method does not correlate highly with the perceived likelihood that other individuals are susceptible to some risk. Instead, the direct method primarily reflects the perceived likelihood that individuals themselves are susceptible to some risk (see Aucote & Gold, 2005;; Chambers, Windschitl, & Suls, 2003;; Kruger & Burrus, 2004). Accordingly, the indirect approach seems to be more informative and is often recommended (e.g., Weinstein & Klein, 1996l for further discussion on methods, see Covey & Davies, 2004).
Optimism bias tends to be amplified when the risky event transpires infrequently (see Harris, Griffin, & Murray, 2008;; Price, Pentecost, & Voth, 2002). That is, optimism bias is especially pronounced when the problem is perceived as infrequent, such as becoming bankrupt, being sued, experiencing a nervous breakdown, being involved in a car accident. In contrast, optimism bias tends to subside when the problem is perceived as relatively prevalent, such as divorce, tooth decay, or disappointing performance in a job interview.
Specifically, in most research studies, participants tend to feel they are especially unlikely to be susceptible to such infrequent events. However, these participants do not assume that other individuals are resistant to such events. As a consequence, they perceive other individuals, but not themselves, as susceptible to infrequent events-manifesting as optimism bias (Harris, Griffin, & Murray, 2008;; Price, Pentecost, & Voth, 2002).
This pattern of observations has been ascribed to egocentric biases (for a discussion of egocentric biases, see Chambers, Windschitl, & Suls, 2003;; Kruger & Burrus, 2004). That is, individuals tend to be more cognizant of how various factors, such as the relative frequency of some event, affect their own susceptibility to this risk. They are, however, less sensitive to how the same factors might affect the susceptibility of other individuals to risks. This egocentric bias arises because individuals tend to focus their attention on personal feelings and states.
Optimism bias also tends to be magnified when the risky event is regarded as controllable-that is, when the event can be prevented through caution, effort, or ingenuity (see Harris, 1996;; Harris, Griffin, & Murray, 2008). Specifically, individuals tend to feel they are not susceptible to events they can control, such as alcoholism, tooth decay, or dismissal from a job. That is, they feel they are more susceptible to events they do not feel they can control, such as being mugged or burgled. However, they perceive other individuals as susceptible even to risks that can be controlled or prevented (Harris, Griffin, & Murray, 2008).
Again, this pattern of findings could be ascribed to egocentric biases. Individuals can readily invoke thoughts, plans, and intentions they could apply to preclude controllable risks. They cannot access these thoughts in other individuals (e.g., Weinstein & Lachendro, 1982). They might, therefore, underestimate the likelihood that other individuals form these plans and intentions.
According to some studies, optimism bias tends to diminish when the risky event is perceived as very severe and consequential. That is, individuals tend to feel they are more susceptible to very consequential and undesirable events, such as heart attacks, but less susceptible to relatively inconsequential or trivial events, such as tooth decay. Severity of events does not affect the perceived likelihood that other individuals are susceptible to these risks (e.g., Harris, Griffin, & Murray, 2008).
According to Harris, Griffin, and Murray (2008), when the event is severe or consequential, individuals become more vigilant. That is, more of their attention is directed towards this event. As a consequence, many defense mechanisms, such as denial, are thwarted.
This pattern of observations contradicts a hypothesis, originally proposed by Weinstein (1980), that consequential events will promote defensive processes, such as denial. That is, Weinstein argued that individuals are more motivated to deny their susceptibility to consequential events, as a means to maintain their wellbeing.
Gold (2008) showed that optimism bias is more pronounced when the events are likely and thus more threatening. However, this observation arose only when participants estimated the susceptibility of themselves to risks before estimating the susceptibility of other individuals to risks. These findings align with the proposition that a motivation to deny risks could underpin the optimism bias. This issue, hence, warrants further attention.
Optimism bias is also amplified when a typical person susceptible to this hazard conforms to some stereotype, such as the assumption that heart attacks are typical if the person is overweight. Similarly, participants often assumed that individuals susceptible to alcoholism, obesity, and sexually transmitted diseases often conform to a specific stereotype. In contrast, participants tend to assume that victims of street robbery, for example, are more diverse and do not conform to a stereotype.
When the typical victim of some risk conforms to a stereotype, participants tend to overrate the likelihood that other individuals are susceptible to this event (Harris, Griffin, & Murray, 2008). This factor, however, does not affect whether individuals themselves feel they are susceptible to this risk (Harris, Griffin, & Murray, 2008).
This pattern of observations has been ascribed to an amalgam of the representative bias (Kahneman & Tversky, 1972) and ease of retrieval or availability (e.g., Haddock, 2002;; Hoch, 1984). To demonstrate, in many tasks, participants often need to estimate the frequency of some events, such as the prevalence of heart attacks in taxi drivers. To estimate this frequency, participants often consider the extent to which these individuals align with the prototype of a person who typifies this event. For example, the prototype of a person who experiences heart attacks might be overweight, lethargic, and stressed. Many taxi drivers might conform to this prototype. Hence, individuals might assume that taxi drivers are susceptible to heart attacks.
Accordingly, if some risk is associated with some stereotype or prototype, individuals can readily form an image of a person who is susceptible to this problem. Because these susceptible individuals are vivid, their prevalence might be overrated.
Antecedents of optimism bias: Characteristics of individuals and contexts
A variety of studies have attempted to uncover the characteristics of individuals that affect the likelihood and magnitude of optimism bias. Most of these factors relate to mood, personality, or self esteem.
Research does indicate that anxiety tends to curb optimism bias (for a review, see Helweg-Larsen & Shepperd, 2001). More specifically, however, anxiety is especially likely to curb optimism bias when the events are perceived as controllable or consequential. That is, if individuals feel the risk cannot be prevented-or is relatively trivial-anxiety does not reduce optimism bias (Harris, Griffin, & Murray, 2008).
According to Harris, Griffin, and Murray (2008), anxious individuals are more vigilant in instances in which they must respond to threats. When a risk is controllable or consequential, individuals need to respond vigilantly, and thus anxious individuals will become especially vigilant in these instances (see MacLeod & Mathews, 1988). This vigilance focuses their attention on possible complications and problems, curbing their optimism.
Self esteem tends to promote the optimism bias (Harris, Griffin, & Murray, 2008). This association between self esteem and optimism bias was especially pronounced when the event was perceived as controllable-that is, when individuals feel they can prevent the risk.
Some forms of optimism bias might be less prominent in collectivist contexts (Heine & Lehman, 1995;; see also Ji, Zhang, Usborne, & Guan, 2004). To illustrate, Heine and Lehman (1995) showed that Canadian individuals showed more pronounced levels of optimism bias than Japanese individuals. According to Heine and Lehman, Japanese individuals are more inclined to adopt a collective or interdependent self construal, in which they define themselves as members of a broader entity rather than detached or independent. Conceivably, this collective self construal tempers the motivation to inflate strengths or achievements-which could partly underpin optimism bias.
Rose, Endo, Windschitl, and Suls (2008) confirmed this pattern of observations. However, collective cultures demonstrated less optimism bias only when the indirect, not the direct, measure was applied.
These findings align to the proposition that optimism bias might coincide with a motivation of individuals to enhance their perception of themselves (see Taylor, Kemeny, Aspinwall, Schneider, Rodriguez, & Herbert, 1992). That is, optimism bias might represent a mechanism to reduce the perceived likelihood of threats, which can protect self esteem.
These findings also align with the perspective adopted by Regan, Snyder, and Kassin (1995) that optimism bias does reflect a need to enhance perceptions of the self. That is, optimism bias is most pronounced when individuals evaluate the extent to which they, or their close friends, are susceptible to risks. However, this bias dissipates when individuals evaluate whether someone who is not relevant to their self concept is susceptible to risks. These findings reject one alternative explanation-that optimism bias merely represents favorable predictions towards individuals rather than collectives.
According to some studies, concerted attempts to diminish this bias are often unsuccessful (Weinstein & Klein, 1995). For example, Weinstein and Klein (1995) showed that optimism biases persist even after participants reflected on personal attributes that might amplify their susceptibility to some risks, such as alcoholism.
Admittedly, some studies have shown that reflections upon how some adverse event might unfold could diminish optimism bias (Anderson, 1983;; Carroll, 1978;; Gregory, Cialdini, & Carpenter, 1982). Likewise, participants are less inclined to demonstrate optimism bias after they are instructed to reflect upon why the event might transpire (Hoch, 1984;; Levi & Pryor, 1987;; Sherman, Skov, Hervitz, & Stock, 1981). Nevertheless, according to Weinstein and Klein (1995), these interventions might be applicable only when the risk is not especially relevant or consequential.
Self affirmation, in which individuals consider their most important value, tends to curb optimism bias. In one study, for example, individuals were asked to write about their most important value (Sherman, Nelson, Bunyan, Cohen, Nussbaum, & Garcia, 2009). Subsequently, they were instructed to evaluate whether or not they are more or less susceptible to heart disease, skin cancer, and other hazards than an average student. Generally, after participants wrote about their most important value, which instills a sense of personal integrity, they conceded they were as susceptible to these hazards as other students. Their optimism bias diminished. That is, self affirmation seems to curb defensive responses.
Optimism bias, although a distortion that could provoke risky behavior, has also been conceptualized as a hallmark of wellbeing. In particular, according to Taylor and Brown (1988), optimism bias-together with illusions of control and unrealistic positive perceptions of the self-can foster positive thoughts and ultimately enhance self esteem and wellbeing.
Nevertheless, optimism biases might instead reflect defensive mechanisms, such as denial, which are inversely related to wellbeing (e.g., Colvin & Block, 1994;; Myers & Brewin, 1996). Furthermore, optimism biases coincide with failures to engage in suitable precautionary acts. Optimism bias, for example, can reduce the likelihood that individuals engage in behaviors that might protect the environment (e.g., Hatfield & Job, 2000).
Even optimism has been shown to evoke a set of complications (e.g., Sweeny & Shepperd, 2010). In general, if people are optimistic about some outcome, such as their performance on an exam, they are more likely to feel disappointed after they receive the feedback. They do not even seem to feel significantly better than pessimistic people immediately before they receive feedback--at least not after controlling actual performance (Sweeny & Shepperd, 2010).
In one study, conducted by Sweeny and Shepperd (2010), participants were asked to specify the extent to which they feel negative emotions, such as distressed, upset, scared, nervous, and afraid, immediately before and after they were informed how they performed on an exam. In addition, before they received this grade, they also estimated the mark they might receive.
Performance expectations were negatively associated with these negative emotions. Nevertheless, this association could be ascribed to the possibility that individuals who had actually performed well experienced both high expectations and fewer negative emotions. Indeed, when actual performance was controlled statistically, no relationship between expectations and emotions was found (Sweeny & Shepperd, 2010). Thus, elevated expectations, unrelated to performance, did not seem to enhance mood before the feedback was presented.
Furthermore, after controlling actual performance and emotions before they received feedback, performance expectations were positively associated with negative emotions (Sweeny & Shepperd, 2010). Thus, elevated expectations, unrelated to performance, may have evoked disappointment.
Many campaigns have been implemented to encourage individuals to implement some precaution, such as install fences around pools. These advertisements should highlight that such risks are not confined to specific individuals, such as negligent parents, but apply to everyone. That is, these campaigns should challenge the assumption that some risk is more prevalent in a specific sector of the population. Furthermore, the frequency of these risks should be highlighted, for example, by listing the names of all individuals who have experienced this problem last year.
Some scholars claim that interventions that are intended to improve safety can promote unsafe behaviors in people. That is, individuals tend to accept a specific level of risk when driving or completing a range of other tasks. If safety is improved--such as when seat belts are mandated or driving speeds are restricted--individuals may engage in riskier behaviors to compensate, boosting their level of risk to an acceptable level.
Peltzman (1975) first proposed this argument from an economic perspective. According to Peltzman, after safety interventions are introduced, the risks, and therefore the costs, associated with faster or riskier driving diminishes, while the gain, such as arriving at a destination sooner, may remain intact. Consequently, individuals will be more inclined to exploit the gain of risky behavior by, for example, driving faster. Peltzman (1975) alluded to the failure of federal regulations to reduce the road toll as evidence of this premise.
The implications of this Peltzman effect is stark. The introduction of seat belts and similar provisions may not appreciably reduce the impact of accidents, because people may drive faster to compensate. Furthermore, because they drive faster, other sectors of the population, such as pedestrians, may be at greater risk. The overall impact partly depends on the extent to which increases in risk generate concomitant increases in gain.
The notion of risk homeostasis, proposed by Wilde (1982), generates a similar prediction but derives these arguments from psychological considerations. According to this model, individuals like to maintain the level of risk at a particular level. Consequently, after safety interventions are introduced, individuals feel compelled to increase the level of risk through other means. Although discussed and assessed extensively, according to Stetzer and Hofmann (1996), previous tests of risk homoestasis have not assessed subjective risk, have depended on aggregate rather than individual data, or have utilized other flawed designs.
Stetzer and Hofmann (1996) conducted a study that assessed risk compensation at an individual level. In essence, they discovered that safety interventions do promote risky behavior, but still tend to diminish risk overall. In this study, participants observed various driving situations on a computer screen. They rated the subjective risk of these situations at a range of speeds. In particular, they specified the personal damage and property damage that would ensue if an unexpected event transpired as well as their sense of perceived risk at each speed. Later, participants were asked to indicate the speed they would drive in each situation. Fewer than 10% of participants exhibited complete homeostasis& yet about 50% of people demonstrated some compensation. That is, as the subjective risk of the situation decreased, participants tended to increase their speed--but not quite to the level predicted from regression analyses derived from the association between subjective risk and the speed of this situation.
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