Behavioral Research

Table of Contents
1 General Description & Theoretical Background
2 Definitions of Perceived Vulnerability in Health Behavior Theories

Measurement and Methodological Issues


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6 Published Examples

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Dispositional Optimism




Illness Representations

  Implementation Intentions
  Intention, Expectation, and Willingness
  Normative Beliefs
  Optimistic Bias
  Perceived Benefits
  Perceived Control
  Perceived Severity
  Perceived Vulnerability
  Self-Reported Behavior
  Social Influence
  Social Support

Perceived Vulnerability
Meg Gerrard and Amy E. Houlihan

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3 Measurement and Methodological Issues

Measurement Issues

A wide array of operationalizations of perceived vulnerability (possibility, probability, likelihood, etc.) exists, and no one definitive measurement scale or strategy has emerged. However, a number of methods of assessment, and distinctions between these methods have emerged.

Absolute Perceived Vulnerability: Many measures of perceived vulnerability focus on absolute measures of risk (van der Pligt, 1998). Absolute measures refer to the perceived likelihood a negative event will occur, e.g., "How likely is it that you will get lung cancer?", "What do you think is the risk that you will get AIDS?" (Gerrard, Gibbons, & Bushman, 1996; Weinstein & Nicolich, 1993). Likert-type response scales are usually utilized for these questions, e.g., 1= "almost certainly will not" to 5 = "almost certainly will" (Joseph, Montgomery, Emmons, Kirscht et al., 1987). Many studies, however, employ scales that call for a numerical probability estimate such as percent likelihood estimates, e.g., "What is the likelihood that you will have an unplanned pregnancy in the next year?"; response scale = 0 to 100%).

A serious weakness of simple absolute vulnerability questions such as these is that they confound expectation, intentions, and current risk behavior, creating two related problems. First, interpretation of estimates made in response to simple absolute assessment of vulnerability requires that knowledge of the respondents' current behavior. For example, a low risk estimate can be interpreted as optimistic from a heavy smoker and accurate from a respondent who has never smoked (Gibbons, Lane, Gerrard, Pomery & Lautrup, 2002). Second, respondents who are anticipating quitting a risk behavior or increasing a precautionary behavior frequently report less risk than their current behavior would suggest. For example, the question "How likely is it that you will get lung cancer?" will elicit a different response from smokers who expect to quit smoking soon than from those who do not anticipate that they will have the motivation or ability to quit in the foreseeable future. Recognition of these problems has lead most researchers to abandon simple absolute measures of personal vulnerability and adopt conditional measures.

Conditional Perceived Vulnerability: Conditional vulnerability measures are designed to elicit consideration of expected or intended future behavior, thus avoiding the confounding of expectations, intentions, and current risk behaviors with perceptions of susceptibility (Ronis, 1992). These measures are often phrased in the subjunctive (e.g., "Imagine that you had six bottles of beer at a party. What is the chance that you will get sick from the beer and throw up?"; Halpern-Felsher, Millstein, Ellen, Adles, Tschann, & Beihll, 2001), and can include consideration of frequency of the risk behaviors, preventive behaviors, etc. (e.g., "What would be the likelihood of pregnancy if you had intercourse more than 3 times per week and used no birth control method?"; Gerrard & Luus, 1995). Thus, conditional measures also allow researchers to assess risk perceptions among people who are not currently engaging in the behavior but may do so in the future. They can also be employed to distinguish between perceived vulnerability when preventive action is taken and when it is not taken (e.g., "If you brush your teeth daily, how likely do you think it is that you will develop gum disease?" followed by "If you do not brush your teeth daily, how likely do you think it is that you will develop gum disease?").

Comparative Perceived Vulnerability: (see Klein, 1996; Klein & Weinstein, 1997). A number of studies have indicated that when asked about their vulnerability, respondents often make automatic comparisons of their own health behavior and characteristics with those of others (Klein, 1996; Klein & Weinstein, 1997). Thus, some recent work has included both absolute perceived vulnerability measures as well as measures of comparative (or "relative") risk (e.g., "Compared to others your age, how likely is it that you will have a smoking-related illness [e.g., lung cancer) at some time in the future?"; Gerrard, Gibbons, Benthin & Hessling, 1996).

Affective Heuristic: Loewenstein and colleagues proposed the risk-as-feelings hypothesis, which suggests emotional reactions often drive risk and precautionary behavior, and that these reactions are the result of a variety of factors that are not necessarily associated with cognitive evaluations of risks, e.g., the vividness of imagined negative consequences, personal experience with outcomes (Loewenstein, Weber, Hsee, & Welch, 2001). Similarly, Slovic and his colleagues suggest that risk decisions stem more from how people feel about the behavior than what they think about the behavior (Slovic, Finucane, Peters, & McGregor, 2003). They argue that people often refer to this "affective pool" when making a decision because it is easier and quicker than weighing the costs and benefits, or recalling specific objective information.

Weinstein and colleagues have developed a 2-item scale designed to assess this feeling component of risk perceptions ("With no flu shot, I would feel that I'm going to get the flu this year," and "With no flu shot, I would feel very vulnerable to the flu"; Weinstein, Kwitel, McCaul, Magnan, Gerrard, & Gibbons, in press).

Windschitl (2003) makes the same distinction, but suggests a somewhat different procedure that assesses both the cognitive evaluation and the feeling component of risk with two separate questions:

    "What is the objective likelihood that you will get skin cancer?" [with detailed instructions on how to use the numeric scale]

    0%                                                                                                                100%

followed by:

    "You just indicated your beliefs about how objectively likely it is that you will get skin cancer. However, at a gut-level, you might feel somewhat more or less vulnerable than your response above suggests. Place a mark on the scale below to indicate how you feel about your chances of getting skin cancer."

    0                                                                                                                       100

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