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How is making a decision for someone else different from deciding for yourself? Ideally, the person making the decision (the "agent") should accurately represent the preferences of the person on whose behalf the decision is made (the "principal"). Often, the principal communicates her preferences to the agent beforehand. An example would be an advance directive for healthcare, where as person expresses preferences for end-of-life medical care. These instructions are used if the person later cannot make decisions for himself.

Ongoing studies examine factors that influence how accurately the agent can predict the principal's preferences. We assess how how competently people in the principal role complete an advance directive. We also assess how competently people in the agent role can use information from the advance directive. Agents are most accurate in predicting the principal's preferences if both parties scored high on competence. A current study uses college students in the role of agent/proxy and their parents in the role of principal/patient.

Chapman, G.B. (2003). Advance directives influence hypothetical treatment decisions by a proxy. Poster presented at the October, 2003 meeting of the Society for Medical Decision Making in Chicago.

Not everyone who gets a flu shot benefits from the vaccination. Some people have an immunological reaction to the vaccine that confers protection, while others do not. In this study we are seeking to identify psychosocial variables that predict immunological response to the flu vaccine. Of particular interest is whether vaccine response will be related to dispositional optimism (a belief that things will go well for me) or optimistic beliefs about one's immune system (a belief that my immune system works well).

Many bikers do not wear bike helmets, despite the fact that helmets reduce the risk of head injury. In an observational study on Rutgers campuses, only 5% of bikers observed were wearing helmets. 500 Rutgers students faculty and staff who bike on or to campus responded to a web survey. The single strongest predictor of bike helmet use was owning a helmet. Attitudes toward bike helmets were moderately correlated with helmet use, while attitude toward bicycling were not. Bikers exhibit some “cost-benefit” reasoning in that they were more likely to wear a helmet if they bicycle frequently, think the risk of injury in the event of an accident is high, and think that helmets are effective in reducing injury. A follow-up survey is planned.

Many people believe that their risk for negative health outcomes is less than their actual level of risk for these outcomes. This bias has been labeled "unrealistic optimism" or the "optimistic bias". An ongoing line of research is to determine what causes this bias and what effect this bias has on future intentions and behavior.

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Decision Making about the Flu Shot

Marco DiBonaventura, Mary Jane Capolongo, Lauren Gross, and Gretchen Chapman

Flu shots are effective in preventing upper respiratory illnesses, even among healthy adults. Yet many people do not receive a yearly flu shot, even when their workplace offers the vaccination at no costs. We conducted a longitudinal study of predictors of flu shot acceptance among healthy adults. Participants in these studies are employees at Rutgers University and a nearby medical school. Thus far our studies have revealed a number of interesting findings:

Predictors of flu shot acceptance include having received the shot in the previous year, perceived effectiveness of the vaccine, perceived risk of side effects, and perceived likelihood of getting the flu if not vaccinated.
Like other preventive health behaviors, flu shots involve an up-front cost and a delayed benefit. The pain of the injection and the inconvenience of getting the shot occur right away, whereas the cases of flu that the shot will prevent would not have occurred until months later. Consequently, one would expect that acceptance of the vaccine would be related to time preferences, or the extent to which future outcomes are valued relative to present ones. In fact, our studies have revealed only a very small relationship between time preferences and flu shot acceptance.
Anticipated worry and regret about the flu predict vaccination better than do perceived likelihood and severity of the flu. Indeed these emotions mediate the relationship between perceived risk and vaccination behavior. Furthermore, the amount of worry or regret that people anticipate feeling does not always match the amount that they actually experience during the flu season. Specifically, anticipated worry reduction motivates flu shot acceptance, but people who do vaccinate end up worrying more than they anticipated they would. Thus, they don't get the peace of mind they expected.
Both attitudes and perceived social norms about the flu shot predict vaccination. We hypothesized that the degree to which the social norm was explicit, or salient, would moderate the strength of the attitude-norm relationship, as well as the norm-behavior relationship. That is, in the presence of an explicit norm, attitudes and norms would be more distinct constructs and hence independent predictors of behavior. We found that exercise behavior exhibited a more explicit norm than flu vaccination behavior and that attitudes and norms toward the latter were more aligned than those toward the former. Contrary to prediction, however, norms did not predict behavior better for the behavior (exercise) with the more explicit norm (2004 Masters Thesis by Marco DiBonaventura).
Health care workers are more likely to get flu shots than are non-clinical employees. This effect of job role on vaccine acceptance is statistically mediated by perceived risk of contracting the flu, knowledge about the vaccine, easy access to the vaccine, pro-Western medicine belief, and social influence (2004 honors thesis by Mary Jane Capolongo).

Chapman, G.B., Brewer, N.T., Coups, E.J., Brownlee, S., Leventhal, H., and Leventhal, E.A. (2001). Value for the future and preventive health behavior. Journal of Experimental Psychology: Applied, 7, 235-250.
Coups, E.J. and Chapman, G.B. (2002). Formation and use of covariation assessment in the real world. Applied Cognitive Psychology, 16, 51-71.
Chapman, G. B., & Coups, E. J. (1999). Predictors of influenza vaccine acceptance among healthy adults. Preventive Medicine, 29, 249-262.
Chapman, G. B., & Coups, E. J. (1999). Time preferences and preventive health behavior: Acceptance of the influenza vaccine. Medical Decision Making, 19, 307-314.
Chapman, G.B., & Coups, E.J. (2004). Worry, regret, and preventive health behavior. Under review.
DiBonaventura, M.D. & Chapman, G.B. (in press). Disruptions in the intention-behavior relationship in preventive health measures: Intention stability and unforeseen barriers, Psychology and Health.
Capolong, M.J., DiBonaventura, M.D., & Chapman, G.B. (in press). Physician heal thyself: Why vaccination rates are higher among clinicians. Annals of Behavioral Medicine.

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Time Preferences

Gretchen Chapman

Many decisions involve trade-offs between immediate outcomes and more delayed outcomes. Time preference is the extent to which the utility of an outcome is discounted because of a delay and can be quantified as a discount rate, or the percent increase in magnitude needed to offset a given delay. For example, if the annual discount rate were 20%, then $1000 now would be just as attractive as $1200 to be received in one year. Subjective discount rates can be inferred from the trade-offs subjects are willing to make. The normative theory of intertemporal choice is discounted utility theory. Actual decisions frequently violate this normative theory (see Chapman, 1998 for a review).

Our research on time preferences has compared intertemporal choice for health and money. We also have examined the relationship between time preference expressed in questionnaire scenarios and real-world behavior that exemplifies intertemporal choice (e.g., getting a flu shot, taking blood pressure medication). Other studies examined how people evaluate very delayed outcomes— outcomes that occur to future generations. Another study is examined cross-cultural differences in inter-generational discounting.

Chapman, G.B. (1998). Sooner or later: The psychology of intertemporal choice. In D.L. Medin (Ed.) The Psychology of Learning and Motivation, vol 38, pp. 83 - 113.
Chapman, G.B. (2001). Time preferences for the very long term. Acta Psychologica, 108, 95-116. (special issue on intertemporal choice).
Chapman, G.B. (2002). Your money or your health: Time preferences and trading money for health. Medical Decision Making, 22, 410-416.
Chapman, G.B. (2003). Time discounting of health outcomes. In George Loewenstein, Daniel Read, & Roy Baumeister (Eds.) Time and Decision: Economic & Psychology Perspectives on Intertemporal Choice. New York: Russell Sage Foundation, pp. 395 - 418.

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Moderators of the Intention-Behavior Relationship

What people intend to do, and what people actually do often differs. What factors cause the discrepancy between intentions to perform health behaviors and actually performing these behaviors? Using a longitudinal dataset assessing aspects of flu vaccination behavior (as well as exercise and weight management), we were able to uncover some explanations: