Wolfgang Gaissmaier

• PhD
• Professor (Full) at University of Konstanz

Marking biased texts is a practical approach to increase media bias awareness among news consumers. However, little is known about the generalizability of such awareness to new topics or unmarked news articles, and the role of machine-generated bias labels in enhancing awareness remains unclear. This study tests how news consumers may be trained an...

Background: Medical RCT effectiveness communication often does not fully acknowledge thetemporal dimension of the trial and its impact on RCT understanding in general practitioners isunclear. The authors therefore tested how trial effectiveness information given as hazard ratio(HR), prolongated failure times (PFT), restricted mean survival times (R...

Decision makers seem to evaluate risky options differently depending on the learning mode—that is, whether they learn about the options’ payoff distributions from a summary description (decisions from description) or by drawing samples from them (decisions from experience). Are there also discrepancies when people choose between a described and an...

There has been much progress in understanding human social learning, including recent studies integrating social information into the reinforcement learning framework. Yet previous studies often assume identical payoffs between observer and demonstrator, overlooking the diversity of social information in real-world interactions. We address this gap...

Misrepresentation of peer behavior has often been observed in college students and may lead to over-expression of alcohol consumption and under-expression of studying. While social norm feedback approaches have had mixed success in addressing these misrepresentations and altering behavior, they may have been too unspecific to be effective and did n...

There has been much progress in understanding human social learning, including recent studies integrating social information into the reinforcement learning framework.Yet previous studies often assume identical payoffs between observer and demonstrator, overlooking the diversity of real-world interactions. We address this gap by introducing a socia...

Disturbingly realistic triage scenarios during the COVID-19 pandemic provide an opportunity for studying discrimination in moral reasoning. Biases and favoritism do not need to be explicit and overt, but can remain implicit and covert. In addition to assessing laypeople’s propensity for engaging in overt discrimination, the present study examines w...

Objective People differ in whether they understand graphical or numerical representations of statistical information better. However, assessing these skills is often not feasible when deciding which representation to select or use. This study investigates whether people choose the representation they understand better, whether this choice can impro...

Background Graphical representation formats (e.g., icon arrays) have been shown to lead to better understanding of the benefits and risks of treatments compared to numbers. We investigate the cognitive processes underlying the effects of format on understanding: how much cognitive effort is required to process numerical and graphical representation...

In this study, we contrast how different benefit and harm information formats and the presence or absence of an ease-of-access nudge may facilitate COVID vaccination uptake for a sample of 620 unvaccinated Dutch adults at a timepoint when the vaccine had been widely available for more than a month. Using a 2 Â 2 between-subjects factorial design, w...

Background: Selective processing of attitude-consistent information is a substantial obstacle in convincing vaccine-skeptical people of the benefits of vaccinations. This study tests (i) which types of information are particularly prone to such selective information processing, and (ii) whether a deliberative (vs. implemental) mindset focusing on p...

Humans are remarkably effective social learners, with several recent studies formalizing this capacity using computational models. However, previous research has often been limited to tasks where observer and demonstrator share the same reward function. In contrast, humans can learn from others who have different preferences, skills, or goals. To s...

We offer experimental evidence for the effect of social sampling on redistributive preferences through a survey experiment using a probabilistic national sample in Germany. We primed respondents to think about different types of social contacts, in particular low- and high-income contacts. We find evidence for an indirect effect in which the primin...

Given the ubiquity of potentially adverse behavioural bias owing to myopic trial-and-error learning, it seems paradoxical that improvements in decision-making performance through conformist social learning, a process widely considered to be bias amplification, still prevail in animal collective behaviour. Here we show, through model analyses and la...

Media bias has a substantial impact on individual and collective perception of news. Effective communication that may counteract its potential negative effects still needs to be developed. In this article, we analyze how to facilitate the detection of media bias with visual and textual aids in the form of (a) a forewarning message, (b) text annotat...

Media coverage possesses a substantial effect on the public perception of events. The way media frames events can significantly alter the beliefs and perceptions of our society. Nevertheless, nearly all media outlets are known to report news in a biased way. While such bias can be introduced by altering the word choice or omitting information, the...

Background During the COVID-19 pandemic, public perceptions and behaviours have had to adapt rapidly to new risk scenarios and radical behavioural restrictions. Aim To identify major drivers of acceptance of protective behaviours during the 4-week transition from virtually no COVID-19 cases to the nationwide lockdown in Germany (3–25 March 2020)....

Physiological synchrony (PS) is defined as the co-occurrence and interdependence of physiological activity between interaction partners. Previous research has uncovered numerous influences on the extent of PS, such as relationship type or individual characteristics. Here, we investigate the influence of acute stress on PS. We do so in a setting in...

Objective: Social media are an increasingly important source of information on the benefits and risks of vaccinations, but the high prevalence of misinformation provides challenges for informed vaccination decisions. It is therefore important to understand which messages are likely to diffuse online and why, and how relevant aspects-such as scient...

Media coverage possesses a substantial effect on the public perception of events. The way media frames events can significantly alter the beliefs and perceptions of our society. Nevertheless, nearly all media outlets are known to report news in a biased way. While such bias can be introduced by altering the word choice or omitting information, the...

Background Since humans are social animals, social relations are incredibly important. However, in cases of contagious diseases such as the flu, social contacts also pose a health risk. According to prominent health behavior change theories, perceiving a risk for one’s health motivates precautionary behaviors. The “behavioral immune system” approac...

Background: Risk-adjusted cancer screening and prevention is a promising and continuously emerging option for improving cancer prevention. It is driven by increasing knowledge of risk factors and the ability to determine them for individual risk prediction. However, there is a knowledge gap between evidence of increased risk and evidence of the ef...

Background: Shared decision making requires evidence to be conveyed to the patient in a way they can easily understand and compare. Patient decision aids facilitate this process. This article reviews the current evidence for how to present numerical probabilities within patient decision aids. Methods: Following the 2013 review method, we assembl...

Background: Decision aid developers have to convey complex task-specific numeric information in a way that minimizes bias and promotes understanding of the options available within a particular decision. Whereas our companion paper summarizes fundamental issues, this article focuses on more complex, task-specific aspects of presenting numeric info...

A bstract Given the ubiquity of potentially suboptimal biases widely observed in animal behaviour, it seems paradoxical that improvements of decision accuracy through the conformist-based social learning is still widely observed. Here we show, through model analyses and online experiments with 467 adult human subjects, that the frequency-based copy...

Cognition is both empowered and limited by representations. The matrix lens model explicates tasks that are based on frequency counts, conditional probabilities, and binary contingencies in a general fashion. Based on a structural analysis of such tasks, the model links several problems and semantic domains and provides a new perspective on represe...

Background: The aim of the study is to investigate how well patients remember the radiologist's name after a radiological examination, and whether giving the patient a business card improves the patient's perception of the radiologist's professionalism and esteem. Methods: In this prospective and randomized two-centre study, a total of 141 patie...

Distinguishing meaningful structure from unpredictable randomness is a key challenge in many domains of life. We examined whether collaborating three-person groups (n = 81) outperform individuals (n = 81) in facing this challenge with a two-part repeated choice task, where outcomes were either serially independent (probabilistic part) or fixed in a...

Risk perceptions typically underlie a complex social dynamic: Risk-related information is transmitted between individuals, this information influences risk perceptions, and risk perceptions influence which information is transmitted. This can lead to a social amplification of risk. We test how stress, a widespread affective state, influences the so...

Background. Informed medical decisions require understanding the benefits and risks of treatments. This entails comparing treatment outcomes to a control group. The incremental risk format has been recommended as it directly visualizes the differences between treatment and control group in 1 graph, whereas they have to be calculated from 2 separate...

Background: Online discussions may impact the willingness to get vaccinated. This experiment tests how groups of individuals with consistent and inconsistent attitudes towards flu vaccination attend to and convey information online, and how they alter their corresponding risk perceptions. Methods: Out of 1859 MTurkers, we pre-selected 208 people...

The public debate around climate change is increasingly polarized. At the same time, the scientific consensus about the causes and consequences of climate change is strong. This inconsistency poses challenges for mitigation and adaptation efforts. The translation of uncertain numerical climate projections into simpler but ambiguous verbal frames ma...

Objective: A shared decision-making approach is suggested for multiple sclerosis (MS) patients. To properly evaluate benefits and risks of different treatment options accordingly, MS patients require sufficient numeracy - the ability to understand quantitative information. It is unknown whether MS affects numeracy. Therefore, we investigated wheth...

Decision quality is often evaluated based on whether decision makers can adequately explain the decision process. Accountability often improves judgment quality because decision makers weigh and integrate information more thoroughly, but it could also hurt judgment processes by disrupting retrieval of previously encountered cases. We investigated t...

Fast-and-frugal trees (FFTs) are simple algorithms that facilitate efficient and accurate decisions based on limited information. But despite their successful use in many applied domains, there is no widely available toolbox that allows anyone to easily create, visualize, and evaluate FFTs. We fill this gap by introducing the R package FFTrees. In...

Background Progressive multifocal leukoencephalopathy (PML) is one of the major risks of natalizumab therapy. Despite introduction of the currently employed PML risk stratification algorithm, the incidence of natalizumab-associated PML cases is not decreasing. Objectives We addressed the following questions: How do natalizumab-treated multiple scl...

Background: Natalizumab (NAT) is associated with the risk of progressive multifocal leukoencephalopathy (PML). Risk stratification algorithms have been developed, however, without detectable reduction of PML incidence. Objective: To evaluate to which extent patients and physicians understand and accept risks associated with NAT treatment. Metho...

Background: While dichotomous tasks and related cognitive strategies have been extensively researched in cognitive psychology, little is known about how primary care practitioners (general practitioners [GPs]) approach ill-defined or polychotomous tasks and how valid or useful their strategies are. Objective: To investigate cognitive strategies...

Treatment choice for localized prostate cancer (PCa) is a controversial issue, and mortality risk is probably the most decisive factor in this regard. The study aimed to compare prostate-cancer-specific mortality risk estimates for different treatment options assigned by patients managed with active surveillance (AS), radical prostatectomy (RP), an...

Why do people gamble? A large body of research suggests that cognitive distortions play an important role in pathological gambling. Many of these distortions are specific cases of a more general misperception of randomness, specifically of an illusory perception of patterns in random sequences. In this article, we provide further evidence for the a...

Decisions in the environmental and in particular the climate domain are burdened with uncertainty. Here, we focus on uncertainties faced by individuals when making decisions about environmental behavior, and we use the statistical sampling framework to develop a classification of different sources of uncertainty they encounter. We then map these so...

Was ist gute Führung? Was sind gute Intuitionen? Beide Fragen hängen zusammen. Ohne Intuition und die Kenntnis, wie sie funktioniert, sind gute Entscheidungen kaum möglich. Beginnen wir mit zwei Geschichten über Intuition: Die erste stammt von einem Vorstand einer Bank, die zweite von einem Headhunter für Führungskräfte.

Background Awareness represents a major modulator for the uptake of preventive measures and healthy life-style choices. Women underestimate the role of cardiovascular diseases as causes of mortality, yet little information is available about their subjective risk awareness. Methods The Berlin Female Risk Evaluation (BEFRI) study included a randomi...

Significance Public risk perception of hazardous events such as contagious outbreaks, terrorist attacks, and climate change are difficult-to-anticipate social phenomena. It is unclear how risk information will spread through social networks, how laypeople influence each other, and what social dynamics generate public opinion. We examine how message...

In a world of known risks, rational theories provide the norms for successful behavior. In a world where not all risks are known and where optimization is not feasible, onrational tools such as heuristics are needed. In comparison to optimization models, heuristics are robust and can lead to more accurate predictions, while saving time and effort....

We describe three major cognitive systems: (1) emotional intuition, (2) deliberate thinking, and (3) intuitive reasoning. Although we argue for the superiority of the third level in most cases, we indicate the value of each level in different circumstances. Not all levels are possible in all circumstances. The distinction between these levels is il...

Others have suggested that increased time pressure, sometimes caused by interruptions, may result in increased diagnostic errors. The authors previously found, however, that increased time pressure alone does not result in increased errors, but they did not test the effect of interruptions. It is unclear whether experience modulates the combined ef...

Purpose Others have suggested that increased time pressure, sometimes caused by interruptions, may result in increased diagnostic errors. The authors previously found, however, that increased time pressure alone does not result in increased errors, but they did not test the effect of interruptions. It is unclear whether experience modulates the com...

Um informierte und selbstbestimmte Entscheidungen von Patientinnen und Patienten möglich zu machen, brauchen wir risikokompetente Ärzte und Ärztinnen sowie eine risikokompetente Öffentlichkeit: Beides kann zum einen durch bessere Fähigkeiten im Umgang mit Gesundheitsstatistiken und zum anderen durch transparente Kommunikation solcher Zahlen erreich...

Does problem gambling arise from an illusion that patterns exist where there are none? Our prior research suggested that “hot hand,” a tendency to perceive illusory streaks in sequences, may be a human universal, tied to an evolutionary history of foraging for clumpy resources. Like other evolved propensities, this tendency might be expressed more...

Every day thousands of individuals need to make critical decisions about their health based on numerical information, yet recent surveys have found that over half the population of the United States is unable to complete basic math problems. How does this lack of numerical ability (also referred to as low numeracy, quantitative illiteracy or statis...

Applying the framework of ecological rationality, the authors studied the adaptivity of group decision making. In detail, they investigated whether groups apply decision strategies conditional on their composition in terms of task-relevant features. The authors focused on the recognition heuristic, so the task-relevant features were the validity of...

Diagnostic errors are thought to arise from cognitive biases associated with System 1 reasoning, which is rapid and unconscious. The primary hypothesis of this study was that the instruction to be slow and thorough will have no advantage in diagnostic accuracy over the instruction to proceed rapidly. Participants were second-year residents who volu...

Making evidence-based decisions often requires comparison of two or more options. Research-based evidence may exist which quantifies how likely the outcomes are for each option. Understanding these numeric estimates improves patients' risk perception and leads to better informed decision making. This paper summarises current "best practices" in com...

Little is known about how physicians provide statistical information to patients, which is important for informed consent. In a survey, obstetricians and gynecologists (N = 142) received statistical information about the benefit and side effects of an antidepressant. They received information in various formats, including event rates (antidepressan...

Background: Prognostic counseling in multiple sclerosis (MS) is difficult because of the high variability of disease progression. Simultaneously, patients and physicians are increasingly confronted with making treatment decisions at an early stage, which requires taking individual prognoses into account to strike a good balance between benefits an...

Individuals have been shown to adaptively select decision strategies depending on the environment structure. Two experiments extended this research to the group level. Subjects (N = 240) worked either individually or in two-person groups, or dyads, on a multi-attribute paired-comparison task. They were randomly assigned to two different environ-men...

Terrorists can strike twice-first, by directly killing people, and second, through dangerous behaviors induced by fear in people's minds. Previous research identified a substantial increase in U.S. traffic fatalities subsequent to the September 11 terrorist attacks, which were accounted for as due to a substitution of driving for flying, induced by...

In October of 2011, the U.S. Preventive Services Task Force released a draft report in which they recommended against using the prostate-specific antigen (PSA) test to screen for prostate cancer. We attempt to show that four factors documented by psychological research can help explain the furor that followed the release of the task force's report....

Psychologists theorize that cognitive reasoning involves two distinct processes: System 1, which is rapid, unconscious, and contextual, and System 2, which is slow, logical, and rational. According to the literature, diagnostic errors arise primarily from System 1 reasoning, and therefore they are associated with rapid diagnosis. This study tested...

Unlike reduced mortality rates, improved survival rates and increased early detection do not prove that cancer screening tests save lives. Nevertheless, these 2 statistics are often used to promote screening. To learn whether primary care physicians understand which statistics provide evidence about whether screening saves lives. Parallel-group, ra...

Policymakers, health professionals, and patients have to understand health statistics to make informed medical decisions. However, health messages often follow a persuasive rather than an informative approach and undermine the idea of informed decisionmaking. The current practice of health risk communication is often biased: Risks are communicated...

Informed medical decision making requires comprehending statistical information. We aimed to improve the understanding of conveying health-related statistical information with graphical representations compared with numerical representations. First, we investigated whether the iconicity of representations (i.e., their abstractness vs. concreteness)...

Statistical illiteracy in health—the inability to understand health statistics—is widespread among the general public. Many people find it hard to accept uncertainty in the first place and, even if they do, basic numerical information is difficult to understand. The problem is aggravated when the benefits and harms of treatment options must be eval...

This report calls for a change in health care, while acknowledging that health care systems are highly complex systems for which there is no simple solution. The starting premise is that one needs to launch and reinforce positive developments among both clinicians and patients. To this end, a vision is offered to transform medical schools into heal...

When probabilistic inferences have to be made from cue values stored in long-term memory, many participants appear to use fast-and-frugal heuristics, such as "take-thebest" (TTB), that assume sequential search of cues. A simultaneous global matching process with cue weights that are appropriately chosen would mimic the decision outcomes, albeit ass...

How eliminating “risk illiteracy” among doctors and patients will lead to better health care decision making. Contrary to popular opinion, one of the main problems in providing uniformly excellent health care is not lack of money but lack of knowledge—on the part of both doctors and patients. The studies in this book show that many doctors and most...

How eliminating “risk illiteracy” among doctors and patients will lead to better health care decision making. Contrary to popular opinion, one of the main problems in providing uniformly excellent health care is not lack of money but lack of knowledge—on the part of both doctors and patients. The studies in this book show that many doctors and most...

We investigated the extent to which the human capacity for recognition helps to forecast political elections: We compared naive recognition-based election forecasts computed from convenience samples of citizens' recognition of party names to (i) standard polling forecasts computed from representative samples of citizens' voting intentions, and to (...

As reflected in the amount of controversy, few areas in psychology have undergone such dramatic conceptual changes in the past decade as the emerging science of heuristics. Heuristics are efficient cognitive processes, conscious or unconscious, that ignore part of the information. Because using heuristics saves effort, the classical view has been t...

How can we accelerate the shift to a new paradigm of patient-centered health care? In this report, a manifesto for change is put forth, while acknowledging that health care systems are highly complex systems for which there is no simple solution. The starting premise is that one needs to launch and reinforce positive developments among both clinici...

Statistical illiteracy in health—the inability to understand health statistics—is wide-spread among the general public. Many people ¿ nd it hard to accept uncertainty in the ¿ rst place and, even if they do, basic numerical information is dif¿ cult to understand. The problem is aggravated when the bene¿ ts and harms of treatment options must be eva...

Viele meiner Kolleginnen und Kollegen waren überrascht, als sie im Zusammenhang mit unserer Forschung zum medizinischen Entscheiden das erste Mal den Begriff "evidenzbasierte Medizin" hörten. Denn wie sollte Medizin sonst funktionieren, als Entscheidungen über Diagnostik und Therapie auf wissenschaftliche Studien zu stützen? Was so selbstverständli...

Natalizumab is associated with the potentially life-threatening side-effect progressive multifocal leukoencephalopathy (PML). Little is known about patients' and physicians' risk estimates and attitudes towards natalizumab treatment. Consecutive natalizumab-treated patients (n = 69) and neurologists (n = 66) in two centres and cooperating private p...

Increased 5-y survival for screened patients is often inferred to mean that fewer patients die of cancer. However, due to several biases, the 5-y survival rate is a misleading metric for evaluating a screening's effectiveness. If physicians are not aware of these issues, informed screening counseling cannot take place. Two questionnaire versions ("...

The recognition heuristic is a noncompensatory strategy for inferring which of two alternatives, one recognized and the other not, scores higher on a criterion. According to it, such inferences are based solely on recognition. We generalize this heuristic to tasks with multiple alternatives, proposing a model of how people identify the consideratio...

In their comment on Marewski et al. (good judgments do not require complex cognition, 2009) Evans and Over (heuristic thinking and human intelligence: a commentary on Marewski, Gaissmaier and Gigerenzer, 2009) conjectured that heuristics can often lead to biases and are not error free. This is a most surprising critique. The computational models of...