Gretchen B. Chapman

Meta-Analysis of the Relationship Between Risk Perception and Health Behavior: The Example of Vaccination

BACKGROUND Risk perceptions are central to many health behavior theories. However, the relationship between risk perceptions and behavior, muddied by instances of inappropriate assessment and analysis, often looks weak. METHOD A meta-analysis of eligible studies assessing the bivariate association between adult vaccination and perceived likelihood, susceptibility, or severity was conducted. RESULTS Thirty-four studies met inclusion criteria (N = 15,988). Risk likelihood (pooled r = .26), susceptibility (pooled r = .24), and severity (pooled r = .16) significantly predicted vaccination behavior. The risk perception-behavior relationship was larger for studies that were prospective, had higher quality risk measures, or had unskewed risk or behavior measures. CONCLUSIONS The consistent relationships between risk perceptions and behavior, larger than suggested by prior meta-analyses, suggest that risk perceptions are rightly placed as core concepts in theories of health behavior.

Temporal discounting and utility for health and money.

In 3 experiments, choices for hypothetical amounts of future health and money showed that, contrary to normative discounted utility theory, the temporal discount rate, or annual percentage increase in value needed to offset a delay, differed for the 2 domains. Domain independence, defined as the low correlation between health and money discount rates relative to the consistency within each domain, was not due to different utility functions for health and money. Consistent with other research, these results suggest that decision domain affects the cognitive processes used. Despite this domain difference, there were some similarities between the 2 domains. Both health and money decisions revealed that discount rates were larger for short delays, small magnitudes, and gains as compared with losses.

Valuing the Future: Temporal Discounting of Health and Money

Normative discounted utility theory specifies that the values of all future outcomes (for example, those related to health and money) should be discounted at a constant rate. Two experiments demonstrated that, contrary to this prescription, decision makers use different discount rates for health-related decisions and money-related decisions. Temporal discount ings for health and money were similar in that both demonstrated two biases previously found in monetary decisions: discount rates were inversely related to magnitude of outcome and length of delay. The relatively large discount rates used by the subjects suggest why it is often difficult to implement preventive health measures that improve future health. Key words: discounting; intertemporal choice; health decisions. (Med Decis Making 1995;15:373- 386)

Heuristics and Biases: Incorporating the Irrelevant: Anchors in Judgments of Belief and Value

Imagine walking down a supermarket aisle and passing an end-of-aisle display of canned tomato soup. A sign on the display says, “Limit 12 per customer.” Would such a sign influence the number of cans you would buy? Would you buy more cans than if the sign said “No limit per customer”? Our intuitions say no, but empirical evidence indicates that purchase behaviors are influenced by such a sign (Wansink, Kent, & Hoch, 1998). Consider another example: A wheel of fortune is spun and stops at the number 65. You are then asked if the percentage of African countries in the United Nations is above or below that number. Could this exercise influence your estimate of the relevant percentage? Although it may seem unlikely, the evidence is that such anchors have an effect: Groups who received larger numbers determined by a wheel of fortune gave higher estimates than groups who received lower numbers, demonstrating that irrelevant anchors influenced these estimates (Tversky & Kahneman, 1974). “Anchoring and adjustment” is one of three well-known heuristics described by Tversky and Kahneman (1974) in a classic paper that also describes the representativeness and availability heuristics. Like the other heuristics, anchoring and adjustment can be a useful way of making judgments. Imagine that you are trying to set a value on an antique chair that you have inherited from a distant aunt. You might recall seeing a very similar chair in slightly better condition at a local antique dealer.

Cue interaction in human contingency judgment

Most studies of human contingency judgment have been based on the assumption that frequency information about one predictor is assessed in isolation of information about other predictors. Recent evidence, however, suggests that the judged predictive strength of one cue is influenced by the predictive strengths of other copresent cues. Two experiments demonstrate that stimuli with the same outcome contingencies may nonetheless have different predictive strengths as the result of cue interaction. The first experiment, in which a within-subject design was used, provides a demonstration of blocking. A stimulus presented in compound with a strong predictor was rated as less predictive than another stimulus that was presented in-compound with a non-predictive cue. In the second experiment, cue interactions in conditioned inhibition were examined. A stimulus gained negative predictive strength as the result of compound presentations with a positive predictor when the outcome was not presented. This negative predictor was compared with an otherwise analogous stimulus that was not presented in compound with a positive predictor. These results support the use of animal-conditioning models as accounts of human contingency learning.

Emotions and Preventive Health Behavior: Worry, Regret, and Influenza Vaccination

The role of worry, regret, and perceived risk in preventive health decisions was explored in a longitudinal questionnaire study on influenza vaccination among 428 university employees. The study yielded 3 main findings. First, ratings of anticipated worry and regret were stronger predictors of vaccination than perceived risk and mediated the effect of risk on vaccination. Second, the anticipated level of emotions differed systematically from experienced emotions, such that vaccinated individuals anticipated more regret and less worry than they actually experienced. Third, anticipated and experienced emotions had implications for subsequent vaccination decisions. Those who did not vaccinate in the 1st year but had high levels of worry and regret were likely to be vaccinated the following year.

Trial Order Affects Cue Interaction in Contingency Judgment

Recent research on contingency judgment indicates that the judged predictiveness of a cue is dependent on the predictive strengths of other cues. Two classes of models correctly predict such cue interaction: associative models and statistical models. However, these models differ in their predictions about the effect of trial order on cue interaction. In five experiments reported here, college students viewed trial-by-trial data regarding several medical symptoms and a disease, judging the predictive strength of each symptom with respect to the disease. The results indicate that trial order influences the manner in which cues interact, but that neither the associative nor the statistical models can fully account for the data pattern. A possible variation of an associative account is discussed.

Long-standing influenza vaccination policy is in accord with individual self-interest but not with the utilitarian optimum

Influenza vaccination is vital for reducing infection-mediated morbidity and mortality. To maximize effectiveness, vaccination programs must anticipate the effects of public perceptions and attitudes on voluntary adherence. A vaccine allocation strategy that is optimal for the population is not necessarily optimal for an individual. For epidemic influenza, the elderly have the greatest risk of influenza mortality, yet children are responsible for most of the transmission. The long-standing recommendations of the Centers for Disease Control follow the dictates of individual self-interest and prioritize the elderly for vaccination. However, preferentially vaccinating children may dramatically reduce community-wide influenza transmission. A potential obstacle to this is that the personal utility of vaccination is lower for children than it is for the elderly. We parameterize an epidemiological game-theoretic model of influenza vaccination with questionnaire data on actual perceptions of influenza and its vaccine to compare Nash equilibria vaccination strategies driven by self-interest with utilitarian strategies for both epidemic and pandemic influenza. Our results reveal possible strategies to bring Nash and utilitarian vaccination levels into alignment.

Preferences for improving and declining sequences of health outcomes

Whereas choices among individual outcomes at different points in time generally show a positive time preference, choices between sequences of outcomes usually show a negative time preference, that is, a preference for improvement. The present studies explored how this preference for improving sequences is moderated by expectations about how sequences are usually experienced. Subjects in three experiments evaluated four types of health sequences with multiple sequence lengths. The length of the sequence and the particular health attribute described influenced both preferences and expectations such that preferences tracked expectations about how the sequences would realistically occur. Several mechanisms by which expectations could influence preferences are discussed. Copyright

Value for the future and preventive health behavior.

Many everyday decisions require trade-offs between immediate and delayed benefits. Although much research has assessed discounting of delayed outcomes by using hypothetical scenarios, little research has examined whether these discounting measures correspond to real-world behavior. Three studies examined the relationship between scenario measures of time preference and preventive health behaviors that require an upfront cost to achieve a long-term benefit. Responses to time preference scenarios showed weak or no relationship to influenza vaccination, adherence to a medication regimen to control high blood pressure, and adherence to cholesterol-lowering medication. The finding that scenario measures of time preference have surprisingly little relationship to actual behaviors exemplifying intertemporal trade-offs places limits on the applications of time preference research to the promotion of preventive health behavior.