Gaëlle Villejoubert

The inverse fallacy: An account of deviations from Bayes’s theorem and the additivity principle

In judging posterior probabilities, people often answer with the inverse conditional probability—a tendency named theinverse fallacy. Participants (N=45) were given a series of probability problems that entailed estimating bothp(H\vbD) andp(≈,H\vbD). The findings revealed that deviations of participants’ estimates from Bayesian calculations and from the additivity principle could be predicted by the corresponding deviations of the inverse probabilities from these relevant normative benchmarks. Methodological and theoretical implications of the distinction between inverse fallacy and base-rate neglect and the generalization of the study of additivity to conditional probabilities are discussed.

Tactful or Doubtful? Expectations of Politeness Explain the Severity Bias in the Interpretation of Probability Phrases

When a statement about the occurrence of a medical condition is qualified by an expression of probability, such as the word possible, listeners interpret the probability of the condition as being higher the more severe the condition. This severity bias can have serious consequences for the well-being of patients. We argue that the bias is due to a misconception of the pragmatic function served by the expression of probability. The more severe the condition, the greater the chance that the listener construes the expression as a politeness marker rather than as an uncertainty marker. When this misconception does not occur, neither should the severity bias. An analysis of interpretations of probability expressions using a membership-function approach validates this account. We discuss the consequences of this bias for the communication of risk within and outside the medical domain.

What lies beneath: Reframing framing effects

Decision framing concerns how individuals build internal representations of problems and how these determine the choices that they make. Research in this area has been dominated by studies of the framing effect, showing reversals in preference associated with the form in which a decision problem is presented. While there are studies that fail to reveal this effect, there is at present no theory that can explain why and when the effect occurs. The purpose of this article is to present a selective review of research and use this to argue for a new framework for considering decision framing, to interpret past studies, and to set an agenda for future research. A simple information-processing model is developed. The model provides the basis for arguing that previous research has taken too narrow a view of how decision problems are internally represented and how these representations are transformed into choice behaviour. In addition, the model is used to highlight the importance of decision content and context.

Interactive insight problem solving

Insight problem solving was investigated with the matchstick algebra problems developed by Knoblich, Ohlsson, Haider, and Rhenius (1999). These problems are false equations expressed with Roman numerals that can be made true bymoving one matchstick. In a first group participants examined a static two-dimensional representation of the false algebraic expression and told the experimenter which matchstick should be moved. In a second group, participants interacted with a three-dimensional representation of the false equation. Success rates in the static group for different problem types replicated the pattern of data reported in Knoblich et al. (1999). However, participants in the interactive group were significantly more likely to achieve insight. Problem-solving success in the static group was best predicted by performance on a test of numeracy, whereas in the interactive group it was best predicted by performance on a test of visuo-spatial reasoning. Implications for process models of problem solving are discussed.

Naturalising problem solving.

A striking feature of people engaged in problem solving outside the psychologist’s laboratory is that it exhibits a great deal of interactivity in a physical space populated with external symbols, artefacts, and, of course, other people. Yet, problem-solving researchers often design experimental procedures in which interactivity is either limited or eliminated. We review traditional areas of problem solving research and introduce new experimental methodologies wherein problems can only be solved by manipulating or restructuring a physical space. In all instances, problem-solving performance is markedly superior than when observed in two-dimensional non-interactive contexts. We suggest that the nature of the processes engaged in solving problems in distributed environments is different than in static environments and should encourage cognitive psychologists to revisit the process models elaborated to account for problem solving behaviour traditionally recorded on the basis of an unmodifiable problem presentation.

Constructing preferences in the physical world: a distributed cognition perspective on preferences and risky choices

Psychological research has firmly established that risk preferences are transient states shaped by past experiences, current knowledge, and feelings as well as the characteristics of the decision environment. We begin this article with a brief review of evidence supporting this conception as well as different psychological theories explaining how preferences are constructed. Next, we introduce the distributed perspective on human cognition and show how it may offer a promising framework for unifying seemingly incompatible accounts. We conclude by suggesting new directions for better capturing the essence of preference construction in laboratory research.

Modus Tollens, Modus Shmollens: Contrapositive reasoning and the pragmatics of negation

The utterance of a negative statement invites the pragmatic inference that some reason exists for the proposition it negates to be true; this pragmatic inference paves the way for the logically unexpected Modus Shmollens inference: “If p then q; not-q; therefore, p.” Experiment 1 shows that a majority of reasoners endorse Modus Shmollens from an explicit major conditional premise and a negative utterance as a minor premise: e.g., reasoners conclude that “the soup tastes like garlic” from the premises “If a soup tastes like garlic, then there is garlic in the soup; Carole tells Didier that there is no garlic in the soup they are eating.” Experiment 2 shows that this effect is mediated by the derivation of a pragmatic inference from negation. We discuss how theories of conditional reasoning can integrate such a pragmatic effect.

Can membership-functions capture the directionality of verbal probabilities?

Verbal probabilities are a common mean for communicating risk and uncertainties in many decision-making settings (e.g., finance, medicine, military). They are considered directional because they elicit a focus on either the outcome occurrence (e.g., there is a chance) or on its non-occurrence (e.g., it is unlikely). According to a quantitative perspective, directionality is dependent on the vague probabilistic meaning conveyed by verbal probabilities—e.g., p(outcome) > .50 = > focus on outcome occurrence. In contrast a more qualitative perspective suggests that directionality depends on contextual factors. The present study tested whether the directionality of verbal probabilities was determined by their vague probabilistic meaning, by contextually manipulated variables (i.e., representativeness and base rate), or by a combination of both. Participants provided their own expressions to describe the guilt of a suspect and then assessed the vague probabilistic meaning and directionality associated with those expressions. Results showed that directionality was mainly determined by the vague probabilistic meaning but also by the base rate of guilt. Although attention focus on the occurrence or the non-occurrence of the target outcome is dependent on vague probabilistic meaning, it cannot be fully accounted for by it.

The interplay between presentation material and decision mode for complex choice preferences

Recent research suggests that, when faced with a choice between several alternatives described with a large number of attributes, people make better choices if they do not consciously ponder over the alternatives but rather perform a distraction task assumed to elicit unconscious thought. Subsequent research attempting to replicate this finding, however, provided mitigated support for its existence. The research reported here contributes to this ongoing debate on two grounds. First, it highlights a methodological confound between qualitative and quantitative presentation material and proposes a novel procedure that can accommodate both. Second, it shows that, whereas conscious deliberation leads to better decisions when alternatives are characterised by quantitative information, the use of a qualitative format for presenting information cancels the advantage of conscious deliberation.

Relevance-driven information search in “pseudodiagnostic” reasoning

When faced with two competing hypotheses, people sometimes prefer to look at multiple sources of information in support of one hypothesis rather than to establish the diagnostic value of a single piece of information for the two hypotheses. This is termed pseudodiagnostic reasoning and has often been understood to reflect, among other things, poor information search strategies. Past research suggests that diagnostic reasoning may be more easily fostered when participants seek data to help in the selection of one of two competing courses of action as opposed to situations where they seek data to help infer which of two competing hypotheses is true. In the experiment reported here, we provide the first empirical evidence demonstrating that manipulating the relevance of the feature for which participants initially receive information determines whether they will make a nominally diagnostic or pseudodiagnostic selection. The discussion of these findings focuses on implications for the ability to engage in diagnostic hypothesis testing.