BACKGROUND. The stomach-derived hormone ghrelin stimulates appetite, but the ghrelin receptor is also expressed in brain circuits involved in motivation and reward. We examined ghrelin effects on decision making beyond food or drug reward using monetary rewards. METHODS. Thirty participants (50% women and 50% men) underwent 2 fMRI scans while receiving i.v. ghrelin or saline in a randomized counterbalanced order. RESULTS. Striatal representations of reward anticipation were unaffected by ghrelin, while activity during anticipation of losses was attenuated. Temporal discounting rates of monetary reward were lower overall in the ghrelin condition, an effect driven by women. Discounting rates were inversely correlated with neural activity in a large cluster within the left parietal lobule that included the angular gyrus. Activity in an overlapping cluster was related to behavioral choices and was suppressed by ghrelin. CONCLUSION. This is, to our knowledge, the first human study to extend the understanding of ghrelins significance beyond the canonical feeding domain or in relation to addictive substances. Contrary to our hypothesis, we found that ghrelin did not affect sensitivity to monetary reward anticipation, but rather resulted in attenuated loss aversion and lower discounting rates for these rewards. Ghrelin may cause a motivational shift toward caloric reward rather than globally promoting the value of reward. TRIAL REGISTRATION. EudraCT 2018-004829-82.

In a seminal paper, Frederick et al. (J Consum Res 36:553-561, 2009) showed that peoples willingness to purchase a consumer good declined dramatically when opportunity costs were made more salient (Cohens d = 0.45-0.85). This finding suggests that people normally do not pay sufficient attention to opportunity costs and as a result make poorer and less efficient decisions, both in private and public domains. To critically assess the strength of opportunity cost neglect, we carried out a systematic review and a meta-analysis including published and non-published experimental work. In total, 39 experimental studies were included in the meta-analysis (N = 14,005). The analysis shows a robust significant effect (Cohens d = 0.22; p < 0.001) of opportunity cost neglect across different domains, albeit the effect is considerably smaller than what was originally estimated by Frederick et al. (2009). Our findings highlight the importance of meta-analyses and replications of initial findings.

Fast-and-slow models of decision-making are commonly invoked to explain economic behaviour. However, past research has focused on human cooperation and generosity and thus largely overlooked situations where there are sharp conflicts between efficiency and equality, or between efficiency and more intuitive moral values (repugnance). Here, we contribute to fill this gap in the literature. We conducted a preregistered experiment (n = 1500 recruited from Prolific) to assess the effects of fast, intuitive decisions, under time pressure versus slow, deliberate decisions, under time delay, on (i) people's distributional preferences and (ii) their attitudes toward repugnant transactions. The results show increased preference for equality and decreased preference for efficiency under time pressure, but no effects on moral repugnance. Exploratory analyses revealed that most of the observed treatment effects in our data were accounted for by women. Our results provide some support for theories that associate controlled cognition with concern for efficiency, and intuitive, emotional responses with inequality aversion. 

Social drinking is common, but it is unclear how moderate levels of alcohol influence decision making. Most prior studies have focused on adverse long-term effects on cognitive and executive function in people with alcohol use disorders (AUD). Some studies have investigated the acute effects of alcohol on decision making in healthy people, but have predominantly used small samples and focused on a narrow selection of tasks related to personal decision making, e.g., delay or probability discounting. Here, we conducted a large (n = 264), preregistered randomized placebo-controlled study (RCT) using a parallel group design, to systematically assess the acute effects of alcohol on measures of decision making in both personal and social domains. We found a robust effect of a 0.6 g/kg dose of alcohol on both moral judgment and altruistic behavior, but no effects on several measures of risk taking or waiting impulsivity. These findings suggest that alcohol at low to moderate doses selectively moderates decision making in the social domain, and promotes utilitarian decisions over those dictated by rule-based ethical principles (deontological). This is consistent with existing theory that emphasizes the dual roles of shortsighted information processing and salient social cues in shaping decisions made under the influence of alcohol. A better understanding of these effects is important to understand altered social functioning during alcohol intoxication.

Background. During the COVID-19 pandemic, the world witnessed a partisan segregation of beliefs toward the global health crisis and its management. Politically motivated reasoning, the tendency to interpret information in accordance with individual motives to protect valued beliefs rather than objectively considering the facts, could represent a key process involved in the polarization of attitudes. The objective of this study was to explore politically motivated reasoning when participants assess information regarding COVID-19. Design. We carried out a preregistered online experiment using a diverse sample (N = 1500) from the United States. Both Republicans and Democrats assessed the same COVID-19-related information about the health effects of lockdowns, social distancing, vaccination, hydroxychloroquine, and wearing face masks. Results. At odds with our prestated hypothesis, we found no evidence in line with politically motivated reasoning when interpreting numerical information about COVID-19. Moreover, we found no evidence supporting the idea that numeric ability or cognitive sophistication bolster politically motivated reasoning in the case of COVID-19. Instead, our findings suggest that participants base their assessment on prior beliefs of the matter. Conclusions. Our findings suggest that politically polarized attitudes toward COVID-19 are more likely to be driven by lack of reasoning than politically motivated reasoning-a finding that opens potential avenues for combating political polarization about important health care topics.

People often choose the option that is better on the most subjectively prominent attribute — the prominence effect. We studied the effect of prominence in health care priority setting and hypothesized that values related to health would trump values related to costs in treatment choices, even when individuals themselves evaluated different treatment options as equally good. We conducted pre-registered experiments with a diverse Swedish sample and a sample of international experts on priority setting in health care (n = 1348). Participants, acting in the role of policy makers, revealed their valuation for different medical treatments in hypothetical scenarios. Participants were systematically inconsistent between preferences expressed through evaluation in a matching task and preferences expressed through choice. In line with our hypothesis, a large proportion of participants (General population: 92%, Experts 84% of all choices) chose treatment options that were better on the health dimension (lower health risk) despite having previously expressed indifference between those options and others that were better on the cost dimension. Thus, we find strong evidence of a prominence effect in health-care priority setting. Our findings provide a psychological explanation for why opportunity costs (i.e., the value of choices not exercised) are neglected in health care priority setting.

People often choose the option that is better on the most subjectively prominent attribute - the prominence effect. We studied the effect of prominence in health care priority setting and hypothesized that values related to health would trump values related to costs in treatment choices, even when individuals themselves evaluated different treatment options as equally good. We conducted pre-registered experiments with a diverse Swedish sample and a sample of international experts on priority setting in health care (n = 1348). Participants, acting in the role of policy makers, revealed their valuation for different medical treatments in hypothetical scenarios. Participants were systematically inconsistent between preferences expressed through evaluation in a matching task and preferences expressed through choice. In line with our hypothesis, a large proportion of participants (General population: 92%, Experts 84% of all choices) chose treatment options that were better on the health dimension (lower health risk) despite having previously expressed indifference between those options and others that were better on the cost dimension. Thus, we find strong evidence of a prominence effect in health-care priority setting. Our findings provide a psychological explanation for why opportunity costs (i.e., the value of choices not exercised) are neglected in health care priority setting.

Due to diffusion of responsibility, majority voting may induce immoral and selfish behavior because voters are rarely solely responsible for the outcome. Across three behavioral experiments (two preregistered; n = 1983), we test this hypothesis in situations where there is a conflict between morality and material self-interest. Participants were randomly assigned to make decisions about extracting money from a charity either in an experimental referendum or individually. We find no evidence that voting induces immoral behavior. Neither do we find that people self-servingly distort their beliefs about their responsibility for the outcome when they vote. If anything, the results suggest that voting makes people less immoral.

Motivated numeracy refers to the idea that people with high reasoning capacity will use that capacity selectively to process information in a manner that protects their own valued beliefs. This concept was introduced in a now classic article by Kahan, Peters, Dawson, & Slovic [2017, Behavioral Public Policy 1, 54-86], who used numeracy to index reasoning capacity, and demonstrated that the tendency to engage in ideologically congruent interpretation of facts increased substantially with peoples numeracy. Despite the importance of this finding, both from a theoretical and practical point of view, there is yet no consensus in the literature about the factual strength of motivated numeracy. We therefore conducted a large-scale replication of Kahan, Peters, Dawson, and Slovic (2017), using a pre-specified analysis plan with strict evaluation criteria. We did not find good evidence for motivated numeracy; there are distinct patterns in our data at odds with the core predictions of the theory, most notably (i) there is ideologically congruent responding that is not moderated by numeracy, and (ii) when there is moderation, ideologically congruent responding occurs only at the highest levels of numeracy. Our findings suggest that the cumulative evidence for motivated numeracy is weaker than previously thought, and that caution is warranted when this feature of human cognition is leveraged to improve science communication on contested topics such as climate change or immigration.

Inaccurate beliefs about procedural fairness often motivate people to act in self-serving and selfish manners. We investigate whether information about a level playing field might mitigate such behaviors. In a pre-registered behavioral experiment ( n = 4 4 4), using a competitive and real-effort task, we manipulate whether participants are informed about the fairness of a competition or not. Following the competition, participants (who either won or lost the competition) decided how to distribute earnings between themselves and their opponent. We show that informing participants about the fairness of the competition reduces selfish behavior among losers, while behavior among winners remains unaffected. Moreover, we show that losers who were not informed about the fairness of the competition incorrectly viewed it as having been unfairly stacked against them (i.e., believing that they encountered significantly more difficult tasks than their opponents). Our findings suggest that information about a level playing field reduces selfish behavior and is important for understanding when and why motivated reasoning about procedural fairness helps people uphold a positive self-image. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Opportunity cost is the foregone benefit of options not chosen. If opportunity costs are neglected in decisions about public policy, there is a high risk that the best options are overlooked. We study opportunity cost neglect in public policy in experiments with members of the general public in Sweden and international experts on priority setting in health care (n = 957). We find strong evidence of opportunity cost neglect in public policy, where participants who acted in the role of policy makers were between six and ten percentage points less likely to invest in a public health program when reminded about opportunity costs (money could fund other health programs). To our surprise, we failed to confirm an effect consistent with opportunity cost neglect in private consumption; but exploratory analyses revealed a substantial age effect that reconciles our findings with previous literature. Young participants showed opportunity cost neglect, while the effect was reversed for old participants. The implications of opportunity cost neglect for public policy are substantial, including misallocation of public resources and an artificially high demand for public spending. (C) 2019 The Author(s). Published by Elsevier B.V.

Dual-process theory is a widely utilized modelling tool in the behavioral sciences. It conceptualizes decision-making as an interaction between two types of cognitive processes, some of them fast and intuitive, others slow and reflective. We make a novel contribution to this literature by exploring differences between adults with clinically diagnosed ADHD and healthy controls for a wide range of behaviors. Given the clinical picture and nature of ADHD symptoms, we had a strong a priori reason to expect differences in intuitive vs reflective processing; and thus an unusually strong case for testing the predictions of dual-process theory. We found mixed results, with overall weaker effects than expected, except for risk taking, where individuals with ADHD showed increased domain sensitivity for gains vs losses. Some of our predictions were supported by the data but other patterns are more difficult to reconcile with theory. On balance, our results provide only limited empirical support for using dual-process theory to understand basic social and economic decision-making.

This paper reports new findings on gender differences in altruism. Conducting a natural field experiment (N = 2,164) we study donation behavior in a naturally occurring environment using a matched donation design. Contrary to previous research, we find that reducing the "price of altruism" by increasing matching efficiency has a significantly stronger effect on females than on males. (C) 2018 Elsevier B.V. All rights reserved.

Using a laboratory experiment in the field, we examine how the framing of a social dilemma, give to or take from a public good, interacts with a policy intervention that enforces a minimum contribution level to the public good. We find significantly higher cooperation in the give frame than in the take frame in our standard public goods experiment. When a minimum contribution level is introduced, contributions are crowded out in the give frame but crowded in in the take frame. Our results show the importance of choosing the frame when making policy recommendations. (JEL C91, H41)

This paper experimentally investigates the altruistic behavior of physicians and whether this behavior is affected by payment system and uncertainty in health outcome. Subjects in the experiment take on the role of physicians and decide on the provision of medical care for different types of patients, who are identical in all respects other than the degree to which a given level of medical treatment affects their health. We investigate physician altruism from the perspective of ethical principles, by categorizing physicians according to how well their treatment decisions align with different principles for priority setting. The experiment shows that many physicians are altruistic toward their patients but also that the degree of altruism varies across patients with different medical needs. We find a strong effect of payment system that is overall unaffected by the introduction of risk and ambiguity in patients health outcomes. There is, however, substantial heterogeneity across individuals, in particular under the capitation payment system where physicians responses to the introduction of uncertainty in patient health are modulated by their own generic risk and ambiguity preferences.

We investigate experimentally the role of institutional formation on the implementation of a binding minimum contribution level to a public good. Groups either face the minimum level exogenously imposed by a central authority, or are allowed to decide for themselves by means of a group vote whether a minimum level should be implemented. We find that a binding minimum contribution level has a positive and substantially significant effect on cooperation. Interestingly, we do not find an additional positive effect of democracy in the context of our experiment; the minimum-level intervention is as effective when exogenously implemented as when endogenously chosen.

The depleting effect of repeated decision making is often referred to as decision fatigue. Understanding how decision fatigue affects medical decision making is important for achieving both efficiency and fairness in health care. In this study, we investigate the potential role of decision fatigue in orthopedic surgeons decisions to operate, exploiting a natural experiment whereby patient allocation to time slots is plausibly randomized at the level of the patient. Our results show that patients who met a surgeon toward the end of his or her work shift were 33 percentage points less likely to be scheduled for an operation compared with those who were seen first. In a logistic regression with doctor-fixed effects and standard errors clustered at the level of the doctor, the odds of operation were estimated to decrease by 10.5% (odds ratio=0.895, pamp;lt;.001; 95% CI [0.842, 0.951]) for each additional patient appointment in the doctors work shift. This pattern in surgeons decision making is consistent with decision fatigue. Because long shifts are common in medicine, the effect of decision fatigue could be substantial and may have important implications for patient outcomes.

Given previous findings from animal studies and small-scale studies in humans, variation in the mu-opioid receptor gene (OPRM1) has been proposed as a strong biological candidate for moderating sensitivity to social rejection. Using a substantially larger sample (N = 490) than previous studies, a prospective genotyping strategy, and preregistered analysis plans, we tested the hypotheses that OPRM1 variation measured by the functional A118G polymorphism (rs1799971) moderates (a) dispositional sensitivity to rejection and feelings of distress following social exclusion and (b) decision making involving social cognition. In three experimental tasks commonly used to assess altruism, reciprocity, and trust in humans, we found no evidence in favor of the hypotheses; nine main tests were preregistered, and all of them yielded small and statistically insignificant estimates. In secondary analyses, we used Bayesian inference and estimation to quantify support for our findings. Taken together, our results strongly suggest that the link between OPRM1 A118G variation and social-rejection sensitivity is weaker than previously thought.

We use skin conductance to measure emotional arousal in subjects who make risky choices under time pressure or time delay. Our results show a strong correlation between subjects skin conductance responses and their risky choices under time pressure but not under time delay. Subjects were more risk taking for higher levels of measured electrodermal activity (skin conductance). In line with descriptive theories of risky choice, the effect was most pronounced for choices involving losses rather than gains. Taken together, our findings indicate that participants under time pressure rely on affect at the point of decision-making. This provides support for behavioral models that recognize the role of emotional brain systems in decision-making under risk.

Background. Whether doctors at the bedside level should be engaged in health care rationing is a controversial topic that has spurred much debate. From an empirical point of view, a key issue is whether there exists a behavioral difference between rationing at the bedside and policy level. Psychological theory suggests that we should indeed expect such a difference, but existing empirical evidence is inconclusive. Objective. To explore whether rationing decisions taken at the bedside level are different from rationing decisions taken at the policy level. Method. Behavioral experiment where participants (n = 573) made rationing decisions in hypothetical scenarios. Participants (medical and nonmedical students) were randomly assigned to either a bedside or a policy condition. Each scenario involved 1 decision, concerning either a life-saving medical treatment or a quality-of-life improving treatment. All scenarios were identical across the bedside and policy condition except for the level of decision making. Results. We found a discrepancy between health care rationing at policy and bedside level for scenarios involving life-saving decisions, where subjects rationed treatments to a greater extent at the policy level compared to bedside level (35.6% v. 29.3%, P = 0.001). Medical students were more likely to ration care compared to nonmedical students. Follow-up questions showed that bedside rationing was more emotionally burdensome than rationing at the policy level, indicating that psychological factors likely play a key role in explaining the observed behavioral differences. We found no difference in rationing between bedside and policy level for quality-of-life improving treatments (54.6% v. 55.7%, P = 0.507). Conclusions. Our results indicate a robust bedside effect in the life-saving domain of health care rationing decisions, thereby adding new insights to the understanding of the malleability of preferences related to resource allocation.

Anger is a powerful emotion and it is important to understand its role in human interaction. Angry individuals may become hostile in their dealings with others, and this has strategic consequences. Battigalli, Dufwenberg, and Smith (2015; BDS) develop a formal framework where frustration and anger affect interaction and shape economic outcomes. This paper presents an experiment designed to test predictions based on versions of the theory that involve no or low responsibility of the punished person. In this specific context, I find only limited, support for the theory: While unfulfilled expectations about material pay-offs generate negative emotions in subjects (which is in line with BDS conceptualization of frustration), these emotions do not affect subjects behavior in the experiment. (C) 2017 Elsevier B.V. All rights reserved.