During the Cold War, logical rationality – consistency axioms, subjective expected utility maximization, Bayesian probability updating – became the bedrock of economics and other social sciences. In the 1970s, logical rationality underwent attack by the heuristics-and-biases program, which interpreted the theory as a universal norm of how individuals should make decisions, although such an interpretation is absent in von Neumann and Morgenstern’s foundational work and dismissed by Savage. Deviations in people’s judgments from the theory were thought to reveal stable cognitive biases, which were in turn thought to underlie social problems, justifying governmental paternalism. In the 1990s, the ecological rationality program entered the field, based on the work of Simon. It moves beyond the narrow bounds of logical rationality and analyzes how individuals and institutions make decisions under uncertainty and intractability. This broader view has shown that many supposed cognitive biases are marks of intelligence rather than irrationality, and that heuristics are indispensable guides in a world of uncertainty. The passionate debate between the three research programs became known as the rationality wars. I provide a brief account from the ‘frontline’ and show how the parties understood in strikingly different ways what the war entailed.

Recent reviews and meta-analyses of metacognitive therapy for schizophrenia-spectrum disorder (SSD) have included uncontrolled studies, single-session interventions, and/or analyses limited to a single form of metacognitive therapy. We sought to evaluate the efficacy of metacognitive therapies more broadly based on controlled trials (CT) of sustained treatments. We conducted a pre-registered meta-analysis of controlled trials that investigated the effects of meta-cognitive therapies on primary positive symptom outcomes, and secondary symptom, function and/or insight measures. Electronic databases were searched up to March 2022 using variants of the keywords, ‘metacognitive therapy’, ‘schizophrenia’, and ‘controlled trial’. Studies were identified and screened according to PRISMA guidelines. Outcomes were assessed with random effects models and sample, intervention, and study quality indices were investigated as potential moderators. Our search identified 44 unique CTs with usable data from 2423 participants. Data were extracted by four investigators with reliability >98%. Results revealed that metacognitive therapies produced significant small-to-moderate effects on delusions (g = 0.32), positive symptoms (g = 0.30) and psychosocial function (g = 0.31), and significant, small effects on cognitive bias (g = 0.25), negative symptoms (g = 0.24), clinical insight (g = 0.29), and social cognition (g = 0.27). Findings were robust in the face of sample differences in age, education, gender, antipsychotic dosage, and duration of illness. Except for social cognition and negative symptoms, effects were evident even in the most rigorous study designs. Thus, results suggest that metacognitive therapies for SSD benefit people, and these benefits transfer to function and illness insight. Future research should modify existing treatments to increase the magnitude of treatment benefits.

The Cognitive Bias (CogBIAS) hypothesis proposes that cognitive biases develop as a function of environmental influences (which determine the valence of biases) and the genetic susceptibility to those influences (which determines the potency of biases). The current study employed a longitudinal, polygenic-by-environment approach to examine the CogBIAS hypothesis. To this end, measures of life experiences and polygenic scores for depression were used to assess the development of memory and interpretation biases in a three-wave sample of adolescents (12–16 years) (N = 337). Using mixed effects modeling, three patterns were revealed. First, positive life experiences (PLEs) were found to diminish negative and enhance positive forms of memory and social interpretation biases. Second, and against expectation, negative life experiences and depression polygenic scores were not associated with any cognitive outcomes, upon adjusting for psychopathology. Finally, and most importantly, the interaction between high polygenic risk and greater PLEs was associated with a stronger positive interpretation bias for social situations. These results provide the first line of polygenic evidence in support of the CogBIAS hypothesis, but also extend this hypothesis by highlighting positive genetic and nuanced environmental influences on the development of cognitive biases across adolescence.

Is it possible to exploit cognitive biases so that a non-professional taster prefers one wine to several other absolutely identical wines? To address this question, three complementary experiments were carried out. Each time, five wines were tasted blind in a tasting laboratory by 24 to 34 tasters. Converging evidence from the experiments shows that participants were not capable of identifying that some of the wines they were tasting were absolutely identical. Moreover, the results show that by providing information about the wines’ ratings, prices, or reputation, tasters’ expectations can be modified, and, as a result, their evaluations of the wines can be altered. Specifically, we show that it is possible to modify the ranking between different wines and to get tasters to prefer a wine over other absolutely identical wines. Finally, a surprising finding was that experienced tasters express stronger opinions and adapt their evaluations more strongly after being given manipulative information on the wines they taste.

Imagine that you have just received a colon cancer diagnosis and need to choosebetween two different surgical treatments. One surgery, the "complicatedsurgery," has a lower mortality rate (16% vs. 20%) but compared to the othersurgery, the "uncomplicated surgery," also carries an additional 1% risk of eachof four serious complications: colostomy, chronic diarrhea, wound infection, oran intermittent bowel obstruction. The complicated surgery dominates theuncomplicated surgery as long as life with complications is preferred overdeath.

In our first survey, 51% of a sample (recruited from the cafeteria of auniversity medical center) selected the dominated alternative, the uncomplicatedsurgery, justifying this choice by saying that the death risks for the twosurgeries were essentially the same and that the uncomplicated surgery avoidedthe risk of complications. In follow-up surveys, preference for theuncomplicated surgery remained relatively consistent (39%-51%) despite (a)presenting the risks in frequencies rather than percents, (b) grouping the 4complications into a single category, or (c) giving the uncomplicated surgery asmall chance of complications as well. Even when a pre-decision "focusingexercise" required people to state directly their preferences between life witheach complication versus death, 49% still chose the uncomplicated surgery.

People’s fear of complications leads them to ignore important differencesbetween treatments. This tendency appears remarkably resistant to debiasingapproaches and likely leads patients to make healthcare decisions that areinconsistent with their own preferences.

Numerical performance information is increasingly important to political decision-making in the public sector. Some have suggested that biases in citizens’ processing of numerical information can be exploited by politicians to skew citizens’ perception of performance. I report on an experiment on how citizens evaluate numerical performance information from a public school context. The experiment is conducted with a large and diverse sample of the Danish population (N=1156). The analysis shows a strong leftmost-digit-bias in citizens’ evaluation of school grading information. Thus, very small changes in reported average grades, which happen to shift the leftmost grade digit, can lead to very large shifts in citizens’ evaluation of performance. The rightmost digit on the grade is almost fully ignored.

Across sign languages, nouns can be derived from verbs through morphophonological changes in movement by (1) movement reduplication and size reduction or (2) size reduction alone. We asked whether these cross-linguistic similarities arise from cognitive biases in how humans construe objects and actions. We tested nonsigners’ sensitivity to differences in noun–verb pairs in American Sign Language (ASL) by asking MTurk workers to match images of actions and objects to videos of ASL noun–verb pairs. Experiment 1a’s match-to-sample paradigm revealed that nonsigners interpreted all signs, regardless of lexical class, as actions. The remaining experiments used a forced-matching procedure to avoid this bias. Counter our predictions, nonsigners associated reduplicated movement with actions not objects (inversing the sign language pattern) and exhibited a minimal bias to associate large movements with actions (as found in sign languages). Whether signs had pantomimic iconicity did not alter nonsigners’ judgments. We speculate that the morphophonological distinctions in noun–verb pairs observed in sign languages did not emerge as a result of cognitive biases, but rather as a result of the linguistic pressures of a growing lexicon and the use of space for verbal morphology. Such pressures may override an initial bias to map reduplicated movement to actions, but nevertheless reflect new iconic mappings shaped by linguistic and cognitive experiences.

This special issue looks at how cognitive bias matters to international law. We wish to shed light on the legal frames, labels, and cognitive biases that shape our understanding of international rules, the application of these rules, and outcomes of international adjudicatory processes. Adopting the behavioral approach to international law, we focus on actual behavior rather than assumed behavior of actors taking part in the international legal process. The central idea of this approach is that human cognitive capacities are limited—or bounded—by a variety of cognitive, emotional and social, or group-based biases. Our aim is to explore how these biases operate on the individual, group, and state level in various spheres of international law. This Symposium therefore looks beyond the traditional understanding of international law as applying between states, and focuses on how individuals, as actors in the international sphere, use international law language to influence other people, to create communities, and to shape identities.

This Introduction first serves to explain the type of shortcuts we make in our decision-making. This description of biases is followed by an overview of behavioral literature in international law that has thus far examined how bias operates in different aspects of international law—in relation to sources, to compliance, and individuals taking part in the international legal process. We then turn to introduce the Symposium and explain its contribution to the existing literature.

How do cognitive biases relevant to foreign policy decision making aggregate in groups? Many tendencies identified in the behavioral decision-making literature—such as reactive devaluation, the intentionality bias, and risk seeking in the domain of losses—have been linked to hawkishness in foreign policy choices, potentially increasing the risk of conflict, but how these “hawkish biases” operate in the small-group contexts in which foreign policy decisions are often made is unknown. We field three large-scale group experiments to test how these biases aggregate in groups. We find that groups are just as susceptible as individuals to these canonical biases, with neither hierarchical nor horizontal group decision-making structures significantly attenuating the magnitude of bias. Moreover, diverse groups perform similarly to more homogeneous ones, exhibiting similar degrees of bias and marginally increased risk of dissension. These results suggest that at least with these types of biases, the “aggregation problem” may be less problematic for psychological theories in international relations than some critics have argued. This has important implications for understanding foreign policy decision making, the role of group processes, and the behavioral revolution in international relations.