Individuals make decisions under uncertainty every day based on incomplete information concerning the potential outcome of the choice or chance levels. The choices individuals make often deviate from the rational or mathematically objective solution. Accordingly, the dynamics of human decision-making are difficult to capture using conventional, linear mathematical models. Here, we present data from a two-choice task with variable risk between sure loss and risky loss to illustrate how a simple nonlinear dynamical system can be employed to capture (...) the dynamics of human decision-making under uncertainty (i.e., multi-stability, bifurcations). We test the feasibility of this model quantitatively and demonstrate how the model can account for up to 86% of the observed choice behavior. The implications of using dynamical models for explaining the nonlinear complexities of human decision-making are discussed, as well as the degree to which nonlinear dynamical systems theory might offer an alternative framework for understanding human decision-making processes. (shrink)

This article surveys the latest research on risky-choice framing effects, focusing on the implications for rational decision-making. An influential program of psychological research suggests that people's judgements and decisions depend on the way in which information is presented, or ‘framed’. In a central choice paradigm, decision-makers seem to adopt different preferences, and different attitudes to risk, depending on whether the options specify the number of people who will be saved or the corresponding number who will die. It is standardly (...) assumed that such responses violate a foundational tenet of rational decision-making, known as the principle of description invariance. We discuss recent theoretical and empirical research that challenges the dominant ‘irrationalist’ narrative. These approaches typically pay close attention to how decision-makers represent decision problems (including their interpretation of numerical quantifiers or predicate choice) and they highlight the need for a more robust characterization of the description invariance principle. We conclude by indicating avenues for future research that could bring us closer to a complete—and potentially rationalizing—explanation of framing effects. (shrink)

Luck egalitarianism is the view that inequalities are justified when and only when a particular condition is met. Recent years have seen considerable debate about the exact nature of the risky choices thought by luck egalitarians to justify inequality. All positions in the debate emphasise the importance of choice, but they differ in the precise details of how choice features in the inequality-justifying condition. The present paper argues for a novel view about the conditions under which risky (...) choices should justify choice in a manner that uncovers ambiguity and flaws in existing positions. It rejects existing accounts and develops a new hypothetical choice based account of inequality-justifying risk. (shrink)

We investigate whether risky choice framing, i.e., the preference of a sure over an equivalent risky option when choosing among gains, and the reverse when choosing among losses, depends on redundancy and density of information available in a task. Redundancy, the saliency of missing information, and density, the description of options in one or multiple chunks, was manipulated in a matrix setup presented in MouselabWeb. On the choice level we found a framing effect only in setups with non-redundant (...) information. On the process level outcomes attracted more acquisitions than probabilities, irrespective of redundancy. A dissociation between acquisition behavior and choice calls for a critical discussion of the limits of process-tracing measures for understanding and predicting choices in decision making tasks. (shrink)

Two kinds of probability expressions, verbal and numerical, have been used to characterize the uncertainty that people face. However, the question of whether verbal and numerical probabilities are cognitively processed in a similar manner remains unresolved. From a levels-of-processing perspective, verbal and numerical probabilities may be processed differently during early sensory processing but similarly in later semantic-associated operations. This event-related potential (ERP) study investigated the neural processing of verbal and numerical probabilities in risky choices. The results showed that (...) verbal probability and numerical probability elicited different N1 amplitudes but that verbal and numerical probabilities elicited similar N2 and P3 waveforms in response to different levels of probability (high to low). These results were consistent with a level-of-processing framework and suggest some internal consistency between the cognitive processing of verbal and numerical probabilities in risky choices. Our findings shed light on possible mechanism underlying probability expression and may provide the neural evidence to support the translation of verbal to numerical probabilities (or vice versa). (shrink)

This article is concerned with how we make decisions based on how problems are presented to us and the effect that the framing of the problem might have on our choices. Current philosophical and psychological accounts of the framing effect in experiments such as the Asian Disease Problem concern reference points and domains. We question the importance of reference points and domains. Instead, we adopt a linguistic perspective focussing on the role of the evaluative polarity evoked by the words (...) - negativeand positive - used to describe the options in the decision problem. We show that the evaluative polarity of the different wordings in the ADP better explain participants’ behaviour than reference points and domains. We propose two models in which the values given to evaluative polarity words directly influence the strength of framing. The results indicate that linguistic considerations regarding evaluative polarity have to be considered in relation to the ADP. The account resembles Fuzzy-Trace-Theory but allows for thestrength of evaluative polarity to directly affect behaviour. In the discussion, we also assess how evaluative polarity relates to negation, antonyms and the communicative frame within which the choices are presented. (shrink)

For a long time, the dominant approach to studying decision making under risk has been to use psychoeconomic functions to account for how behavior deviates from the normative prescriptions of expected value maximization. While this neo-Bernoullian tradition has advanced the field in various ways—such as identifying seminal phenomena of risky choice —it contains a major shortcoming: Psychoeconomic curves are mute with regard to the cognitive mechanisms underlying risky choice. This neglect of the mechanisms both limits the explanatory value (...) of neo-Bernoullian models and fails to provide guidance for designing effective interventions to improve decision making. Here we showcase a recent “attentional turn” in research on risk choice that elaborates how deviations from normative prescriptions can result from imbalances in attention allocation and that thus promises to overcome the challenges of the neo-Bernoullian tradition. We argue that a comprehensive understanding of preference formation in risky choice must provide an account on a mechanistic level, and we delineate directions in which existing theories that rely on attentional processes may be extended to achieve this objective. (shrink)

Our aim in this paper was to establish an empirical evaluation for similarity effects modeled by Rubinstein; Azipurua et al.; Leland; and Sileo. These tests are conducted through a sensitivity analysis of two well-known examples of expected utility (EU) independence violations. We found that subjective similarity reported by respondents was explained very well by objective measures suggested in the similarity literature. The empirical results of this analysis also show that: (1) the likelihood of selection for the riskier choice increases as (...) the pair becomes more similar, (2) these choice patterns are consistent with well-known independence violations of expected utility, and (3) a significant proportion of individuals exhibit intransitive choice patterns predicted under similarity effects, but not allowed under generalized expected utility models for risky choice. (shrink)

Loss aversion can occur in riskless and risky choices. We present novel evidence on both in a non-student sample (660 randomly selected customers of a car manufacturer). We measure loss aversion in riskless choice in endowment effect experiments within and between subjects and find similar levels of average loss aversion in both. The subjects of the within study also participate in a simple lottery choice task which arguably measures loss aversion in risky choices. We find substantial (...) heterogeneity in both measures of loss aversion. Loss aversion in riskless choice and loss aversion in risky choice are strongly positively correlated, but on average riskless loss aversion is higher than risky loss aversion. We find that in both choice tasks, loss aversion increases in age, income, and wealth, and decreases in education. Our results provide novel supportive input to the debate about the reality of loss aversion. (shrink)

Individuals make decisions under uncertainty every day. Decisions are based on in- complete information concerning the potential outcome or the predicted likelihood with which events occur. In addition, individuals’ choices often deviate from the rational or mathematically objective solution. Accordingly, the dynamics of human decision making are difficult to capture using conventional, linear mathematical models. Here, we present data from a 2-choice task with variable risk between sure loss and risky loss to illustrate how a simple nonlinear dynamical (...) system can be employed to capture the dynamics of human decision making under uncertainty (i.e., multistability, bifurcations). We test the feasibility of this model quantitatively and demonstrate how the model can account for up to 86% of the observed choice behavior. The implications of using dynamical models for explaining the nonlin- ear complexities of human decision making are discussed as well as the degree to which the theory of nonlinear dynamical systems might offer an alternative framework for understanding human decision making processes. (shrink)

In the time of the COVID-19 pandemic, people are often faced with uncertain risky choice. Risky choice will be affected by different descriptions of the event’s gain or loss framework, this phenomenon is known as the framing effect. With the continuous expansion and in-depth study of frame effects in the field of risky choice, researchers have found that the are quite different in different situations. People have different interpretations of the same event at different psychological distances, and (...) will also be affected by their own emotions. Therefore, the current study examines the common influence of task frame, spatial distance, and trait emotion on risky choice through two studies. Study 1 used a 2 × 2 inter-subject design, and the dependent variable is the choice of the rescue plan for the classic “Asian disease” problem. The results revealed that trait anger did not predict individuals’ risky choice preferences, and high trait anxiety led individuals to be more risk-averse. The framing effect exists in risky choice, and individuals prefer risk seeking in the loss frame. Study 2 used a 2 × 2 × 2 three-factor inter-subject design in which the dependent variable is the choice of rescue plan. The results indicate that the framing effect also exists in risky choice, and individuals prefer risk seeking in a loss frame. High trait anxiety lead individuals to be more risk-averse, while trait anger has no significant predictive effect on risk preference. Distant spatial distance lead individuals to increase their preference for risk-seeking under the gain frame, which leads to the disappearance of the framing effect. In conclusion, trait anxiety and spatial distance have a certain degree of influence on risky choice under the framework of gain and loss. (shrink)

A framing bias shows risk aversion in problems framed as “gains” and risk seeking in problems framed as “losses,” even when these are objectively equivalent and probabilities and outcomes values are explicitly provided. We test this framing bias in situations where decision makers rely on their own experience, sampling the problem's options and seeing the outcomes before making a choice. In Experiment 1, we replicate the framing bias in description-based decisions and find risk indifference in gains and losses in experience-based (...) decisions. Predictions of an Instance-Based Learning model suggest that objective probabilities as well as the number of samples taken are factors that contribute to the lack of framing effect. We test these two factors in Experiment 2 and find no framing effect when a few samples are taken but when large samples are taken, the framing effect appears regardless of the objective probability values. Implications of behavioral results and cognitive modeling are discussed. (shrink)

In this paper, I discuss the risks of brain injuries in collision and contact sports and make a proposal to address them without limiting the autonomy of athletes. I aim to analyse the circumstances of profound uncertainty that athletes are facing in terms of the long-term impact of brain injuries. My strategy is to circumvent drastic measures in dealing with such risks, such as banning certain sports or changing their nature by introducing constitutive rule changes, and to scaffold individual autonomy (...) instead. I will focus on two aspects. First, I address the choice whether to take up or continue to play a risky sport given the mentioned profound level of ignorance. I argue that we can scaffold autonomy to make rational choices, particularly by enabling the application of heuristics. Second, I discuss performative skills that can help to prevent brain injuries. It is important to consider collision and contact sports as instances of joint action. The performance of others is an important factor in determining the level of risk in such sports. Hence, supporting athlete’s skills to prevent collisions can reduce the risk of brain injury. I conjecture ways to scaffold players’ skills and performance with this aim in mind. (shrink)

In this paper, I discuss the risks of brain injuries in collision and contact sports and make a proposal to address them without limiting the autonomy of athletes. I aim to analyse the circumstances of profound uncertainty that athletes are facing in terms of the long-term impact of brain injuries. My strategy is to circumvent drastic measures in dealing with such risks, such as banning certain sports or changing their nature by introducing constitutive rule changes, and to scaffold individual autonomy (...) instead. I will focus on two aspects. First, I address the choice whether to take up or continue to play a risky sport given the mentioned profound level of ignorance. I argue that we can scaffold autonomy to make rational choices, particularly by enabling the application of heuristics. Second, I discuss performative skills that can help to prevent brain injuries. It is important to consider collision and contact sports as instances of joint action. The performance of others is an important factor in determining the level of risk in such sports. Hence, supporting athlete’s skills to prevent collisions can reduce the risk of brain injury. I conjecture ways to scaffold players’ skills and performance with this aim in mind. (shrink)

Cocaine use disorder is associated with maladaptive decision-making behavior, which strongly contributes to the harmful consequences of chronic drug use. Prior research has shown that cocaine users exhibit impaired neuropsychological test performances, particularly with regard to attention, learning, and memory but also in executive functions such as decision-making and impulse control. However, to what extent cocaine users show impaired decision-making under risk without feedback has not yet been investigated systematically. Therefore, to examine risk-taking behavior, 31 chronic cocaine users and 26 (...) stimulant-naïve healthy controls who were part of the Zurich Cocaine Cognition Study, performed the Randomized Lottery Task (RALT) with winning lotteries consisting of an uncertain and a certain prospect. Results revealed that risky decisions were associated with male sex, increased cocaine use in the past year, higher cocaine concentrations in the hair, and younger age. In addition, higher levels of cocaine in the hair and cumulative lifetime consumption were associated with risky decisions, whereas potentially confounding factors including cognition and psychiatric symptoms had no significant effect. Taken together, our results indicate that cocaine users who increased their consumption over a period of 1 year show deficits in the processing of risky information accompanied with increased risk-taking. Future research should analyse whether risky decisions could potentially serve as a prognostic marker for cocaine use disorder. (shrink)

How do people pursue rewards in risky environments, where some outcomes should be avoided at all costs? We investigate how participant search for spatially correlated rewards in scenarios where one must avoid sampling rewards below a given threshold. This requires not only the balancing of exploration and exploitation, but also reasoning about how to avoid potentially risky areas of the search space. Within risky versions of the spatially correlated multi‐armed bandit task, we show that participants’ behavior is (...) aligned well with a Gaussian process function learning algorithm, which chooses points based on a safe optimization routine. Moreover, using leave‐one‐block‐out cross‐validation, we find that participants adapt their sampling behavior to the riskiness of the task, although the underlying function learning mechanism remains relatively unchanged. These results show that participants can adapt their search behavior to the adversity of the environment and enrich our understanding of adaptive behavior in the face of risk and uncertainty. (shrink)

The Expanse does not provide an easy answer to the vexing question on making a decision when competing, but considering conflicts of values on the show can help us reason about tough choices in real life. Sometimes, scientific progress conflicts with the prudential value of self‐preservation. This chapter explains three ways of understanding value conflicts: as situations in which every option is forbidden, situations in which every option is permissible, or situations in which some options are obligatory and some (...) options are forbidden. The idea that all these different kinds of value can be traded with a common currency is tempting. But contra Keats, beauty is not truth; and it certainly is not goodness, as Tolstoy says. Epistemic, moral, prudential, and aesthetic values are very different. (shrink)

Recently proposed models of risky choice imply systematic violations of transitivity of preference. This study explored whether people show the predicted intransitivity of the two models proposed to account for the certainty effect in Allais paradoxes. In order to distinguish “true” violations from those produced by “error,” a model was fit in which each choice can have a different error rate and each person can have a different pattern of preferences that need not be transitive. Error rate for a (...) choice is estimated from preference reversals between repeated presentations of the same choice. Results showed that few people repeated intransitive patterns. We can retain the hypothesis that all participants were transitive. (shrink)

The early stages of the COVID-19 pandemic exposed large portions of the global populations to increased daily stressors. Research on risky choice in medical contexts suggests that affect-rich choice options promote less-advantageous decision strategies compared with affect-poor options, causing an “affect gap” in decision making. The current experiments (total N = 437, age range: 21–82) sought to test whether negative pandemic-related affect would lower expected-value (EV) maximisation within individuals. In Experiment 1, participants indicated how much they would be willing (...) to pay to avoid specific pandemic experiences (e.g. “not being able to gather in groups”), and then chose among pairs of risky prospects that involved pandemic experiences or subjectively-equivalent monetary losses. EV maximising was lower for pandemic experiences than for equivalent monetary losses. Experiment 2 replicated this finding, and further demonstrated a moderating role of decision perspective. EV maximising was greater in decisions made for another person than in decisions made for oneself. These findings highlight potential strategies for boosting decision making under affect-rich real-world conditions. (shrink)

Most discussions of the potential of new information technologies (IT) for education have taken one of two forms: enthusiastic proclamations of the revolutionary impact that IT can have for teaching and learning in school and nonschool settings, or dire warnings of the terrible fraud being perpetrated on society about the educational potential of IT. This essay attempts to avoid exaggerated optimism and pessimism about IT and education, while avoiding the trite oversimplification that technology is “neutral” and can be used for (...) good or bad purposes. Our view is guided by the assumption that it is actually very difficult, if not impossible, in many cases to sort out benefits from costs—the very same outcomes can be viewed as favorable or unfavorable, depending on other assumptions about their effects. We propose a posttechnocratic view of IT that recognizes the multiplicity of effects, the indeterminacy and inseparability of consequences, and the difficulty of isolating “good” and “bad” outcomes. As an example of posttechnocratic analysis, the recent educational concern about censorship and the Internet is discussed to demonstrate how educational policy choices are often more complex and ambiguous than we might wish. (shrink)

The choice argument against sweatshop regulations states that public officials should not prohibit workers from accepting jobs that require long hours, low pay, and poor working conditions, because enforcing such regulations would be disrespectful to the workers who choose to work in sweatshops. Critics of the choice argument reply that these regulations can be justified when workers only choose to work in sweatshops because they lack acceptable alternatives and are unable to coordinate to achieve better conditions for all workers. My (...) thesis is that the presence of unacceptable alternatives to sweatshop labor or barriers to coordination cannot justify sweatshop regulations such as minimum wage and maximum hour laws. Although officials should promote alternatives to difficult and dangerous sweatshop labor, they should not do so by limiting workers’ and employers’ options through coercive regulation. And the fact that sweatshop workers may face coordination problems does not undermine the claim that sweatshop workers choose to work in sweatshops, just as other workers face coordination problems but nevertheless make occupational choices. Furthermore, efforts to restrict sweatshop workers’ choices are morally risky and may not promote workers’ wellbeing or wellbeing in general. (shrink)

Humans regularly pursue activities characterized by dramatic success or failure outcomes where, critically, the chances of success depend on the time invested working toward it. How should people allocate time between suchmake‐or‐breakchallenges and safe alternatives, where rewards are more predictable (e.g., linear) functions of performance? We present a formal framework for studying time allocation between these two types of activities, and we explore optimal behavior in both one‐shot and dynamic versions of the problem. In the one‐shot version, we illustrate striking (...) discontinuities in the optimal time allocation policy as we gradually change the parameters of the decision‐making problem. In the dynamic version, we formulate the optimal strategy—defined by agiving‐upthreshold—which adaptively dictates when people should stop pursuing the make‐or‐break goal. We then show that this strategy is computationally inaccessible for humans, and we explore boundedly rational alternatives. We compare the performance of the optimal model against (a) a myopic giving‐up threshold that is easier to compute, and even simpler heuristic strategies that either (b) only decide whether or not to start pursuing the goal and never give up or (c) consider giving up at a fixed number of control points. Comparing strategies across environments, we investigate the cost and behavioral implications of sidestepping the computational burden of full rationality. (shrink)

The Expanse does not provide an easy answer to the vexing question on making a decision when competing, but considering conflicts of values on the show can help us reason about tough choices in real life. Sometimes, scientific progress conflicts with the prudential value of self-preservation. This chapter explains three ways of understanding value conflicts: as situations in which every option is forbidden, situations in which every option is permissible, or situations in which some options are obligatory and some (...) options are forbidden. The idea that all these different kinds of value can be traded with a common currency is tempting. But contra Keats, beauty is not truth; and it certainly is not goodness, as Tolstoy says. Epistemic, moral, prudential, and aesthetic values are very different. (shrink)

From the viewpoint of the independence axiom of expected utility theory, an interesting empirical dynamic choice problem involves the presence of a “global risk,” that is, a chance of losing everything whichever safe or risky option is chosen. In this experimental study, participants have to allocate real money between a safe and a risky project. Treatment variable is the particular decision stage at which a global risk is resolved: (i) before the investment decision; (ii) after the investment decision, (...) but before the resolution of the decision risk; (iii) after the resolution of the decision risk. The baseline treatment is without global risk. Our goal is to investigate the isolation effect and the principle of timing independence under the different timing options of the global risk. In addition, we examine the role played by anticipated and experienced emotions in the choice problem. Main findings are a violation of the isolation effect, and support for the principle of timing independence. Although behavior across the different global risk cases shows similarities, we observe clear differences in people’s affective responses. This may be responsible for the conflicting results observed in earlier experiments. Dependent on the timing of the global risk different combinations of anticipated and experienced emotions influence decision making. (shrink)

In this paper, I aim to shed some light on the nature and value of this neglected but important virtue of trustfulness. First, I briefly introduce the nature of trust and trust relationships and explain why they are essentially risky. Second, I examine the nature of trustfulness mainly by comparing it with other traits such as distrustfulness, gullibility, and prudent reliance. I then argue that its attitudinal element of respecting the trustee as a person—that is, respecting her as an (...) agent capable of free choice—is what distinguishes trustfulness from other traits. I also show why trustfulness is not only intrinsically admirable but also necessary for building a harmonious community. Then I add some further remarks on trustfulness that might help better understand this virtue. Finally, I conclude this paper after addressing some possible objections. (shrink)

The problem of how to make optimal choices in the face of risk arises in both economics/decision theory and also evolutionary biology; in the former, ‘optimal’ means utility maximizing, while in the latter it means fitness maximizing. This article explores the links, thematic and formal, between the economic and evolutionary theories of optimal choice in risky situations, with particular reference to the relationship between utility and fitness. It is argued that the link is strongest between evolution and ‘nonexpected’ (...) utility theory, rather than traditional expected utility theory. (shrink)

In the last decade, a number of studies in the behavioural sciences, particularly in psychology and economics, have explored the complexity of individual risk behaviour and its underlying factors. Most previous studies have examined the influences of various socio-economic, cognitive, biological and psychological factors on human decision-making however, the relationship between the decision-makers’ risk preferences and occupational background has not received much empirical attention. Accordingly, in the current study, we investigated how occupational background, together with decision-making framing (e.g., variations in (...) decision domain, context, presentation of risk and utility ratios), influence participants’ risk preferences for decision options with equivalent expected utility. Our novel findings indicate that risk preferences may vary among individuals from different occupational backgrounds. As such, when the task was framed in gain terms, participants who mostly deal with health/safety-related risks on a day-to-day basis (high-risk occupations) were predominantly risk-averse (avoiding risky options), while participants who mostly deal with financial/social risks (white-collar occupations) were prone to risk-seeking behaviour (avoiding certain options). Specifically, in “high-risk” occupations, participants’ pattern of choices changed from risk-averse in gain scenarios to risk-seeking in loss scenarios. However, the opposite pattern of risk preferences was found in participants with “white-collar” occupations. Our findings indicate that decision-makers’ occupational backgrounds influence risk preferences under some circumstances. (shrink)

The “Asian disease” problem (Tversky & Kahneman, 1981) demonstrated behaviour in contradiction to the invariance axiom of EU theory. However, the risky choice behaviour was simply seen by the equate-to-differentiate model as a choice between the best possible outcomes or a choice between the worst possible outcomes. It was then argued that a way in which frame influences choice is through the perceived difference between possible outcomes. A “judgement” task was designed to examine whether the knowledge of “the value (...) difference between each possible outcome and the certain outcome” will permit prediction of preference in the choice pattern related to the Asian disease problem. Participants were exposed to an anthrax disease problem (the original or probabilistic version of the Asian disease problem) and a SARS problem (the fuzzy version of the Asian disease problem). It was shown that the empirical evidence in relation to the Asian disease problem could be satisfactorily accounted for by the generalised weak dominance strategy revealed by the judgement results. (shrink)

In two experiments, participants had to choose between a sure and a risky option. The sure option was presented either in a gain or a loss frame. Need was defined as a minimum score the participants had to reach. Moreover, choices were made under two different time constraints and with three different levels of induced need to be reached within a fixed number of trials. The two experiments differed with respect to the specific amounts to win and the (...) need levels. The $$2 \times 2 \times 3$$2×2×3 design was a within-subject design. Data were evaluated on an overall and on a group level, the latter based on participants’ stated risk preference and on revealed preferences using cluster analysis across subjects. Overall, the results showed riskier behavior when the choice options were presented as losses as compared to gains and when the induced need was highest. Time limits enhanced the framing effect. (shrink)

From the viewpoint of the independence axiom of expected utility theory, an interesting empirical dynamic choice problem involves the presence of a “global risk,” that is, a chance of losing everything whichever safe or risky option is chosen. In this experimental study, participants have to allocate real money between a safe and a risky project. Treatment variable is the particular decision stage at which a global risk is resolved: (i) before the investment decision; (ii) after the investment decision, (...) but before the resolution of the decision risk; (iii) after the resolution of the decision risk. The baseline treatment is without global risk. Our goal is to investigate the isolation effect and the principle of timing independence under the different timing options of the global risk. In addition, we examine the role played by anticipated and experienced emotions in the choice problem. Main findings are a violation of the isolation effect, and support for the principle of timing independence. Although behavior across the different global risk cases shows similarities, we observe clear differences in people’s affective responses. This may be responsible for the conflicting results observed in earlier experiments. Dependent on the timing of the global risk different combinations of anticipated and experienced emotions influence decision making. (shrink)

Experimental results on the Ellsberg paradox typically reveal behavior that is commonly interpreted as ambiguity aversion. The experiments reported in the current paper find the objective probabilities for drawing a red ball that make subjects indifferent between various risky and uncertain Ellsberg bets. They allow us to examine the predictive power of alternative principles of choice under uncertainty, including the objective maximin and Hurwicz criteria, the sure-thing principle, and the principle of insufficient reason. Contrary to our expectations, the principle (...) of insufficient reason performed substantially better than rival theories in our experiment, with ambiguity aversion appearing only as a secondary phenomenon. (shrink)