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.

In March 2024, Daniel Kahneman – the man who did perhaps more than anyone else to shape the field of behavioural public policy – died. He is among a small handful of scholars who have had a huge effect on my own career, and in this essay – the first in a series of essays in a special section of the Journal that honour him – I reflect on how his work inspired much of my own.

How does the general public perceive immigrants, whom do they think of when thinking about “immigrants,” and to what extent are these perceptions related to the actual composition of immigrant populations? We use three representative online surveys in the United States, South Africa, and Switzerland (total N = 2,778) to extend existing work on the perception of immigrants in terms of geographic coverage and individual characteristics. We also relate these responses to official statistics on immigration and integration patterns. In all three countries, there are significant discrepancies between perceptions of immigrants and their real proportion in the population and characteristics. Although we observe clear country differences, there is a striking pattern of people associating “immigrants” with “asylum seekers” in all three countries. We consider two possible explanations for the differences between perceptions and facts: the representativeness heuristic and the affect heuristic. In contrast to previous research, we find only partial support for the representativeness heuristic, whereas the results are consistent with the affect heuristic. We conclude that images of “immigrants” are largely shaped by pre-existing attitudes.

Nudging is a policy tool that steers people’s behavior through noncoercive psychological pushes. This has consequences for people’s lives to varying degrees. For example, the nudge of a sticker of a fly in a urinal encourages peeing inside a urinal, while an organ donation default brings people to agree to donating their organs after their decease. Governments do not yet systematically examine which nudges have to be subjected to all safeguards of the rule of law—for example, parliamentary control, judicial review, or compliance with legal principles such as proportionality. This article argues that a legal doctrine is necessary to carry out this examination. Moreover, it contributes to the development of such a doctrine, using the approach of the European Court of Human Rights as a source of inspiration. The doctrine consists of a “de minimis” principle for nudges: Public institutions only need to ensure that a nudge complies with rule of law safeguards when the nudge has substantial consequences. In addition, the doctrine includes a criterion to determine which nudges have such substantial consequences. In particular, it is argued that a nudge should be subjected to at least some safeguards when it has a serious effect on people’s autonomy.

This paper presents a toolkit of heuristics for enabling non-professionals to design for wellbeing, merging design, psychology, and ergonomics. It demystifies design, focusing on happiness and long-term wellbeing, making design principles accessible to all. This toolkit narrows the divide between design theory and practice, advocating design as a tool to enhance life for individuals and society.

Political scientists have proposed that party cues can be used to compensate for the public's well-documented lack of substantive political knowledge, but some critics have argued that applying party cues is more difficult than assumed. We argue that this debate has proven intractable in part because scholars have used ambiguous normative criteria to evaluate judgments. We use a unique task and clear normative criteria to evaluate the use of party cues in making political judgments among two samples: a sample of state legislators and an online sample of the public. We find that the public sample performs poorly when using cues to make judgments. State legislators make much more accurate judgments on average than even the most attentive segment of the public and are more likely to place less weight on irrelevant cues when making judgments, although there is evidence that both samples performed worse with the inclusion of non-diagnostic cues. We conclude with a discussion of the relevance of the results, which we interpret as showing that party cue use is more difficult than theorized, and discuss some practical implications of the findings.

Finding paths is a fundamental problem in graph theory and algorithm design due to its many applications. Recently, this problem has been considered on temporal graphs, where edges may change over a discrete time domain. The analysis of graphs has also taken into account the relevance of vertex properties, modeled by assigning to vertices labels or colors. In this work, we deal with a problem that, given a static or temporal graph, whose vertices are colored graph looks for a path such that (1) the vertices of the path have distinct colors and (2) that path includes the maximum number of colors. We analyze the approximation complexity of the problem on static and temporal graphs, and we prove an inapproximability bound. Then, we consider the problem on temporal graphs, and we design a heuristic for it. We present an experimental evaluation of our heuristic, both on synthetic and real-world graphs. The experimental results show that for many instances of the problem, our method is able to return near-optimal solutions.

Several legal scholars have recently argued that U.S. tort law’s physical-emotional distinction commits tort to the objectionable position of mind-body dualism, but they have not considered the distinction’s role as an aid to judicial cognition and decision-making. Drawing primarily on the law of negligent infliction of emotional distress, this essay argues that tort’s physical-emotional distinction is not a relic of mind-body dualism but a heuristic that judges have used to structure and simplify the difficult but unavoidable task of drawing lines between legally cognizable and non-cognizable harm. The analysis has at least three normative implications: (1) users of tort’s physical-emotional distinction should clarify that they neither endorse dualism nor depreciate emotional harm; (2) because judicial expertise may not extend to the task of drawing lines between legally cognizable and non-cognizable harm, judicial performance in this area may be more adequate than critics suggest; and (3) although it may not be possible to determine the optimal way of drawing lines between legally cognizable and non-cognizable emotional harm, moral-philosophical tools such as Rawlsian and Scanlonian contractualism may be able to identify partial or pro tanto considerations for choosing among different ways of doing so.

Any threat to use nuclear weapons inherently carries the possibility of escalation to a level such that both parties in a conflict, and likely many others, would be destroyed. Yet nuclear weapons are also seen as necessary for securing the very things that would be destroyed if the weapons were ever used. The fix for this nuclear dilemma relies on the strategy of deterrence. Deterrence provides a rationale for why nuclear weapons are necessary, even though they may seem dangerous. But the practice of deterrence involves less intentionality and agency than is usually assumed. The success of deterrence relies partially on luck as well as unrealistic assumptions about human behavior. Rather than a strategic necessity, deterrence may be an institutionalized behavior, accepted because it has always been practiced rather than because it makes sense. Assessing the ethics of deterrence and nuclear weapons requires engaging with these issues.

Are human beings irredeemably irrational? If so, why? In this article, I suggest that we need a broader appreciation of thought and reasoning to understand why people get things wrong. Although we can never escape cognitive bias, learning to recognize and understand it can help us push back against its dangers – and in particular to do so collectively and collaboratively.

GC Harcourt made many fundamental and essential contributions to the development of capital investment theory – most famously via his development of the Cambridge Capital Controversies, exposing conceptual and analytical flaws and contradictions in neoclassical approaches to defining and measuring capital. Relatedly, Harcourt also made essential contributions to our understanding of how accounting rules, used by real-world businesses to guide their investment decision-making, create anomalies and deficiencies in the accumulation of capital at a microeconomic level – with significant, deleterious consequences for the accumulation of capital at a macroeconomic level. In developing Harcourt’s contributions, this paper links Harcourt’s early insights about accounting rules with subsequent developments in behavioural economic models of business decision-making, thus aligning Harcourt’s contributions with insights from behavioural models of investment decision-making. These insights are then combined in showing how the misapplication of investment appraisal criteria at a microeconomic level contributes to under-investment and investment volatility in the macroeconomy, with negative implications for output, employment, labour productivity, wages and cyclical volatility.

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 this paper, we explain how FFTs work, introduce a new class of algorithms called fan for constructing FFTs, and provide a tutorial for using the FFTrees package. We then conduct a simulation across ten real-world datasets to test how well FFTs created by FFTrees can predict data. Simulation results show that FFTs created by FFTrees can predict data as well as popular classification algorithms such as regression and random forests, while remaining simple enough for anyone to understand and use.

How do mushroom foragers make safe and efficient decisions under uncertainty, or deal with the genuine risks of misidentification and poisoning? This article is an inquiry into ecological rationality, heuristics, perception, and decision-making in mushroom foraging. By surveying 894 Finnish mushroom foragers, this article illustrates how socially learned rules of thumb and heuristics are used in mushroom foraging, and how simple heuristics are often complemented by more complex and intuitive decision-making. The results illustrate how traditional foraging cultures have evolved precautionary heuristics to deal with uncertainties and poisonous species, and how foragers develop selective attention through experience. The study invites us to consider whether other human foraging cultures might use heuristics similarly, how and why such traditions have culturally evolved, and whether early hunter-gatherers might have used simple heuristics to deal with uncertainty.

We investigated the extent to which the human capacity for recognition helps to forecast political elections: We compared naïve 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 (ii) simple—and typically very accurate—wisdom-of-crowds-forecasts computed from the same convenience samples of citizens’ aggregated hunches about election results. Results from four major German elections show that mere recognition of party names forecast the parties’ electoral success fairly well. Recognition-based forecasts were most competitive with the other models when forecasting the smaller parties’ success and for small sample sizes. However, wisdom-of-crowds-forecasts outperformed recognition-based forecasts in most cases. It seems that wisdom-of-crowds-forecasts are able to draw on the benefits of recognition while at the same time avoiding its downsides, such as lack of discrimination among very famous parties or recognition caused by factors unrelated to electoral success. Yet it seems that a simple extension of the recognition-based forecasts—asking people what proportion of the population would recognize a party instead of whether they themselves recognize it—is also able to eliminate these downsides.