Probability Size Matters: The Effect of Foreground-Only versus Foreground+Background Graphs on Risk Aversion Diminishes with Larger Probabilities.

Graphs are increasingly recommended for improving decision-making and promoting risk-avoidant behaviors. Graphs that depict only the number of people affected by a risk ("foreground-only" displays) tend to increase perceived risk and risk aversion (e.g., willingness to get vaccinated), as compared to graphs that also depict the number of people at risk for harm ("foreground+background" displays). However, previous research examining these "foreground-only effects" has focused on relatively low-probability risks (<10%), limiting generalizability to communications about larger risks. In two experiments, we systematically investigated the moderating role of probability size on foreground-only effects, using a wide range of probability sizes (from 0.1% to 40%). Additionally, we examined the moderating role of the size of the risk reduction, that is, the extent to which a protective behavior reduces the risk. Across both experiments, foreground-only effects on perceived risk and risk aversion were weaker for larger probabilities. Experiment 2 also revealed that foreground-only effects were weaker for smaller risk reductions, while foreground-only displays decreased understanding of absolute risk magnitudes independently of probability size. These findings suggest that the greater effectiveness of foreground-only versus foreground+background displays for increasing perceived risk and risk aversion diminishes with larger probability sizes and smaller risk reductions. Moreover, if the goal is to promote understanding of absolute risk magnitudes, foreground+background displays should be used rather than foreground-only displays regardless of probability size. Our findings also help to refine and extend existing theoretical accounts of foreground-only effects to situations involving a wide range of probability sizes.

Designing Graphs that Promote Both Risk Understanding and Behavior Change.

Graphs show promise for improving communications about different types of risks, including health risks, financial risks, and climate risks. However, graph designs that are effective at meeting one important risk communication goal (promoting risk-avoidant behaviors) can at the same time compromise another key goal (improving risk understanding). We developed and tested simple bar graphs aimed at accomplishing these two goals simultaneously. We manipulated two design features in graphs, namely, whether graphs depicted the number of people affected by a risk and those at risk of harm ("foreground+background") versus only those affected ("foreground-only"), and the presence versus absence of simple numerical labels above bars. Foreground-only displays were associated with larger risk perceptions and risk-avoidant behavior (i.e., willingness to take a drug for heart attack prevention) than foreground+background displays, regardless of the presence of labels. Foreground-only graphs also hindered risk understanding when labels were not present. However, the presence of labels significantly improved understanding, eliminating the detrimental effect of foreground-only displays. Labels also led to more positive user evaluations of the graphs, but did not affect risk-avoidant behavior. Using process modeling we identified mediators (risk perceptions, understanding, user evaluations) that explained the effect of display type on risk-avoidant behavior. Our findings contribute new evidence to the graph design literature: unlike what was previously feared, we demonstrate that it is possible to design foreground-only graphs that promote intentions for behavior change without a detrimental effect on risk understanding. Implications for the design of graphical risk communications and decision support are discussed.

Designing Graphs to Communicate Risks: Understanding How the Choice of Graphical Format Influences Decision Making.

Previous research suggests that the choice of graphical format for communicating risk information affects both understanding of the risk magnitude and the likelihood of acting to decrease risk. However, the mechanisms through which these effects work are poorly understood. To explore these mechanisms using a real-world scenario, we examined the relative impact of two graphical displays for depicting the risk of exposure to unexploded ammunition during potential land redevelopment. One display depicted only the foreground information graphically (a bar graph of the number of people harmed), and a second depicted the foreground and background graphically (a stacked bar graph representing both the number harmed and at risk). We presented 296 participants with either the foreground-only or the foreground and background graphical display and measured a broad set of outcome variables, examining (1) the graphical display effect on each of the outcome measures and (2) the pathways by which any display effects work to influence decision making. We found that the foreground-only graphical display increased perceived likelihood and experienced fear, which produced greater worry, which in turn increased risk aversion. In addition, a positive evaluation of the communication materials increased support for policies related to land redevelopment, whether those policies were risk taking or risk mitigating. Finally, the foreground-only graphical display decreased understanding of the risk magnitude, showing that approaches to accomplish one risk communication goal (promoting risk-averse decisions) may do so at the expense of another goal (increasing understanding).

Effects of Numerical Versus Foreground-Only Icon Displays on Understanding of Risk Magnitudes.

The aim of this work is to advance knowledge of how to measure gist and verbatim understanding of risk magnitude information and to apply this knowledge to address whether graphics that focus on the number of people affected (the numerator of the risk ratio, i.e., the foreground) are effective displays for increasing (a) understanding of absolute and relative risk magnitudes and (b) risk avoidance. In 2 experiments, the authors examined the effects of a graphical display that used icons to represent the foreground information on measures of understanding (Experiments 1 and 2) and on perceived risk, affect, and risk aversion (Experiment 2). Consistent with prior findings, this foreground-only graphical display increased perceived risk and risk aversion; however, it also led to decreased understanding of absolute (although not relative) risk magnitudes. Methodologically, this work shows the importance of distinguishing understanding of absolute risk from understanding of relative risk magnitudes, and the need to assess gist knowledge of both types of risk. Substantively, this work shows that although using foreground-only graphical displays is an appealing risk communication strategy to increase risk aversion, doing so comes at the cost of decreased understanding of absolute risk magnitudes.

A social values analysis of parental decision making.

Social values theory was used to examine how parents make decisions for their adolescent children. Social values theory states that decision making for others is based on the social value of an action, leading to a norm for how to decide for others, whereas self decisions are influenced by a number of additional factors. Consistent with a risk-aversion norm, in hypothetical health and safety scenarios parents made more risk and inconvenience affected self decisions more risk-averse decisions for their adolescent children than for themselves. Further, the level of riske than decisions for one's child. A second study showed that the norm was stronger for decisions for one's child than for oneself and more related to parents' decisions for their child than for themselves. In sum, parents' decisions for their children seem to be largely determined by a norm stating how they are supposed to decide, at least in the domain of health and safety. Implications for both the judgment and decision making and parenting literatures are discussed.

Communicating quantitative information about unexploded ordnance risks to the public.

Military base closures have left 600,000 acres of U.S. land contaminated with unexploded ordnance (UXO). Recent research has demonstrated a method for quantifying the probability of residual UXO harming future land users. Here, we explore how a community neighboring a closed, UXO-contaminated military base responds to the probabilistic risk information this method produces. We explore how probabilistic information affects their risk understanding, risk management preferences, risk perceptions, and worry. We test eight different communication formats employing varying combinations of textual risk descriptions, comparative risk information, stacked bar graphs illustrating the proportion of future land users at risk, and textual summaries and/or graphical histograms presenting uncertainty. We find that stacked bar graphs double the odds of correctly reporting the probability of harm and decrease the perceived risk, compared to textual descriptions. Providing histograms or summary uncertainty information decreases the odds of correctly reporting the probability of harm by about one-half, compared to communications without uncertainty information. We also find that risk communication formats do not alter risk management preferences. We recommend that as EPA reevaluates its UXO risk management policies in the coming year, the agency shift to quantitative rather than its current qualitative approach to assessing and communicating UXO risks.

Thinking without knowing: Psychological and behavioral consequences of unjustified confidence regarding blackjack strategy.

In two studies, we explored potential psychological and behavioral consequences of unjustified confidence, including outcome expectations, anxiety, risk taking, and information search and consideration. Study 1 employed an individual-differences approach to examine how participants' confidence regarding their knowledge of blackjack strategy, controlling for their actual knowledge, correlated with these hypothesized psychological and behavioral variables. Study 2 manipulated participants' confidence levels to examine these effects. Across the two studies, greater unjustified confidence led to larger bets (a measure of risk taking) and reduced use of hints designed to improve play (information search and consideration). Unjustified confidence also increased participants' outcome expectations and lowered anxiety levels. Implications of these findings, such as for educational interventions, are discussed.

Perceived Social Norms Guide Health Care Decisions for Oneself and Others: A Cross-Sectional Experiment in a US Online Panel.

BACKGROUND: Global aging has increased the reliance on surrogates to make health care decisions for others. We investigated the differences between making health care decisions and predicting health care decisions, self-other differences for made and predicted health care decisions, and the roles of perceived social norms, emotional closeness, empathy, age, and gender. METHODS: Participants (N = 2037) from a nationally representative US panel were randomly assigned to make or to predict a health care decision. They were also randomly assigned to 1 of 5 recipients: themselves, a loved one 60 y or older, a loved one younger than 60 y, a distant acquaintance 60 y or older, or a distant acquaintance younger than 60 y. Hypothetical health care scenarios depicted choices between relatively safe lower-risk treatments with a good chance of yielding mild health improvements versus higher-risk treatments that offered a moderate chance of substantial health improvements. Participants reported their likelihood of choosing lower- versus higher-risk treatments, their perceptions of family and friends' approval of risky health care decisions, and their empathy. RESULTS: We present 3 key findings. First, made decisions involved less risk taking than predicted decisions, especially for distant others. Second, predicted decisions were similar for others and oneself, but made decisions were less risk taking for others than oneself. People predicted that loved ones would be less risk taking than distant others would be. Third, perceived social norms were more strongly associated than empathy with made and predicted decisions. LIMITATIONS: Hypothetical scenarios may not adequately represent emotional processes in health care decision making. CONCLUSIONS: Perceived social norms may sway people to take less risk in health care decisions, especially when making decisions for others. These findings have implications for improving surrogate decision making. HIGHLIGHTS: People made less risky health care decisions for others than for themselves, even though they predicted others would make decisions similar to their own. This has implications for understanding how surrogates apply the substituted judgment standard when making decisions for patients.Perceived social norms were more strongly related to decisions than treatment-recipient (relationship closeness, age) and decision-maker (age, gender, empathy) characteristics. Those who perceived that avoiding health care risks was valued by their social group were less likely to choose risky medical treatments.Understanding the power of perceived social norms in shaping surrogates' decisions may help physicians to engage surrogates in shared decision making.Knowledge of perceived social norms may facilitate the design of decision aids for surrogates.

Identifying the Effects of Unjustified Confidence versus Overconfidence: Lessons Learned from Two Analytic Methods.

One of the most common findings in behavioral decision research is that people have unrealistic beliefs about how much they know. However, demonstrating that misplaced confidence exists does not necessarily mean that there are costs to it. This paper contrasts two approaches toward answering whether misplaced confidence is good or bad, which we have labeled the overconfidence and unjustified confidence approach. We first consider conceptual and analytic issues distinguishing these approaches. Then, we provide findings from a set of simulations designed to determine when the approaches produce different conclusions across a range of possible confidence-knowledge-outcome relationships. Finally, we illustrate the main findings from the simulations with three empirical examples drawn from our own data. We conclude that the unjustified confidence approach is typically the preferred approach, both because it is appropriate for testing a larger set of psychological mechanisms as well as for methodological reasons.

Sizing up information distortion: quantifying its effect on the subjective values of choice options.

When choosing between options, people often distort new information in a direction that favors their developing preference. Such information distortion is widespread and robust, but less is known about the magnitude of its effects. In particular, research has not quantified the effects of distortion relative to the values of the choice options. In two experiments, we manipulated participants' initial preferences in choices between risky three-outcome monetary gambles (win, lose, or neither) by varying the order of five information items (e.g., amount to win, chance of losing). In Experiment 1 (N = 397), the effect of initial information on gambles' certainty equivalents (subjective values) was mediated by the distortion of later information. The indirect effect on the difference between gambles' certainty equivalents averaged 27% of the gambles' mean expected value. In Experiment 2 (N = 791), we increased the difference between gambles on a later information item to overcome the effect of initial information on participants' choices. The required change averaged 31% of the gambles' mean expected value. We conclude that the effects of information distortion can be substantial.

The greater ability of graphical versus numerical displays to increase risk avoidance involves a common mechanism.

By displaying a risk reduction of 50% graphically rather than numerically, Stone, Yates, and Parker significantly increased professed risk-avoidant behavior. The current experiments replicated this effect at various risk ratios. Specifically, participants were willing to spend more money to reduce a risk when the risk information was displayed by asterisks rather than by numbers for risk-reduction ratios ranging from 3% to 97%. Transforming the amount participants were willing to spend to logarithms significantly improved a linear fit to the data, suggesting that participants convert this variable within the decision-making process. Moreover, a log-linear model affords an exceptional fit to both the graphical and numerical data, suggesting that a graphical presentation elicits the same decision-making mechanism as does the numerical display. In addition, the data also suggest that each person removed from harm is weighted more by some additional factor in the graphical compared to the numerical presentations.