Thibault Gajdos

French National Centre for Scientific Research | CNRS · Laboratoire de psychologie cognitive

The present study aims at deciphering the effect of a high-intensity interval exercise on cognitive processes involved in perceptual decision-making through computational modelling. To that end, participants performed a perceptual decision task (RDK) before and after a high-intensity interval exercise (8 x 5min, 85 +- 8 % HRmax). Cognitive processe...

This article introduces an integrated and biologically-inspired theory of decision-making, motor preparation, and motor execution. The theory is formalized as an extension of the diffusion model, in which diffusive accumulated evidence from the decision-making process is continuously conveyed to motor preparation brain areas, where it is filtered out...

Purpose The combined effects of acute hypoxia and exercise on cognition remain to be clarified. We investigated the effect of speed climbing to high altitude on reactivity and inhibitory control in elite climbers. Methods Eleven elite climbers performed a speed ascent of the Mont-Blanc (4810 m) and were evaluated pre- (at 1000 m) and immediately p...

Computational models of decision making are becoming increasingly popular to interpret reaction time and choice data in terms of decision and non-decision related processes. But current evidence remains scarce as to whether parameters of a mathematical model such as the Drift Diffusion Model (DDM) can recover genuine latent psychological processes....

This article presents a theory in which motor execution in perceptual decision-making tasks is determined by the same evolving decision variable that drives response time. The theory builds upon recent insights from the neuroscience of decision-making and motor control. It is formalized as an extension of Ratcliff's diffusion model, and assumes tha...

To assess the influence of carbohydrate-electrolyte (CHO-E) intakes on cognitive and physical performances, we carried out an ecological protocol simulating the load variations of a biking race. Eight well-trained athletes completed an outdoor mountain biking time-trial race (TT) (19.6 ± 0.40 km length; 81 min ± 15 min) interspersed with three 10 m...

Many popular internet platforms use so-called collaborative filtering systems to give personalized recommendations to their users, based on other users who provided similar ratings for some items. We propose a novel approach to such recommendation systems by viewing a recommendation as a way to extend an agent’s expressed preferences, which are typ...

This study aimed to apply electromyographic techniques and distributional analyses to test whether an increase in the strength of stimulus-response mapping could explain the mechanisms underlying the joint Simon effect. Within a single protocol, participants performed a Simon task and a Go/NoGo task in isolation, and a joint Go/NoGo task with a co-...

We elaborated an index, the Interference Distribution Index, which allows quantifying the relation between response times and the size of the interference effect. This index is associated with an intuitive graphical representation, the Lorenz-interference plot. We show that this index has some convenient properties in terms of sensitivity to change...

Understanding how people rate their confidence is critical for the characterization of a wide range of perceptual, memory, motor and cognitive processes. To enable the continued exploration of these processes, we created a large database of confidence studies spanning a broad set of paradigms, participant populations and fields of study. The data f...

Understanding how people rate their confidence is critical for characterizing a wide range of perceptual, memory, motor, and cognitive processes. However, progress has been slowed by the difficulty of collecting new data and the unavailability of existing data. To address this issue, we created a large database of confidence studies spanning a broa...

Social risk equity is concerned with the comparative evaluation of social risk distributions, which are probability distributions over the potential sets of fatalities. In the approach to the evaluation of social risk equity introduced by Gajdos, Weymark, and Zoli (Shared destinies and the measurement of social risk equity, Annals of Operations Res...

While recent studies have emphasized the role of metacognitive judgments in social interactions, whether social context might reciprocally impact individuals’ metacognition remains an open question. It has been proposed that such might be the case in situations involving stereotype threat. Here, we provide the first empirical test of this hypothesi...

Supplementary materials. Supplementary materials, including Tables S1 to S5 and experimental instructions for the stereotype threat and no-threat conditions. (DOCX)

Data. Experimental data. (CSV)

DataReadme. Details of the format of the experimental data. (TXT)

Delta plots are a graphical representation of the time course of an experimental effect. They are constructed by plotting the difference between equivalent response time (RT) quantiles in each condition against their mean. Delta plots are widely used in cognitive control research to evaluate the efficiency of inhibitory control mechanisms in tasks...

Established models of perceptual metacognition, the ability to evaluate our perceptual judgements, posit that perceptual confidence depends on the strength or quality of feedforward sensory evidence. However, alternative theoretical accounts suggest the entire perception-action cycle, and not only variation in sensory evidence, is monitored when ev...

In a recent study, the differential effects of prolonged physiologically challenging exercise upon two executive processes (cognitive control and working memory) were investigated. However, the impact of exercise on the selective inhibition task employed was debatable and needed further analysis to dissociate the effects induced by exercise intensi...

In a recent study, the differential effects of prolonged physiologically challenging exercise upon two executive processes (cognitive control and working memory) have been investigated. However, the impact of exercise on the selective inhibition task remained debatable and needed further analysis to dissociate the effects induced by exercise intens...

The present study was conducted to decipher whether a spatial correspondence effect can emerge in Go/No Go tasks (cSE, in reference to Donders’ type c task) performed in isolation (participant alone in the cubicle). To this aim, a single participant was centrally positioned in front of a device and was required to respond by a hand key-press to th...

Established models of perceptual metacognition, the ability to evaluate our perceptual judgments, posit that perceptual confidence depends on the strength or quality of feedforward sensory evidence. However, alternative theoretical accounts suggest the entire perception-action cycle, and not only variation in sensory evidence, is monitored when eva...

Response capture is a widespread and extensively studied phenomenon, in particular in decision tasks involving response conflict. Its intensity is routinely quantified by conditional accuracy function (CAF). We argue that this method might be misleading, and propose an alternative approach, the error location function (ELF). While CAF provides the...

Response capture is a widespread and extensively studied phenomenon, in particu- lar in decision tasks involving response conflict. Its intensity is routinely quantified by Conditional Accuracy Function (CAF). We argue that this method might be mislead- ing, and propose an alternative approach, the Error Location Function (ELF). While CAF provides th...

We propose and operationalize normative principles to guide social decisions when individuals potentially have imprecise and heterogeneous beliefs, in addition to conflicting tastes or interests. To do so we adapt the standard Pareto principle to those preference comparisons that are robust to belief imprecision and characterize social preferences...

Using a simple theoretical decision model and an original database, we were able to elicit the distribution of the utility value of having a child with Down syndrome for a large sample of French pregnant women (n = 28,341) between 2003 and 2007. We found that, on a scale where the value of a fetal death is 0 and the value of a healthy child is 1, t...

Metacognitive judgments of performance can be retrospective (such as confidence in past choices) or prospective (such as a prediction of success). Several lines of evidence indicate that these two aspects of metacognition are dissociable, suggesting they rely on distinct cues or cognitive resources. However, because prospective and retrospective ju...

We provide a generalization of Harsanyi's (1955) aggregation theorem to the case of incomplete preferences at the individual and social level. Individuals and society have possibly incomplete expected utility preferences that are represented by sets of expected utility functions. Under Pareto indifference, social preferences are represented through...

We compare three alternative methods for eliciting retrospective confidence in the context of a simple perceptual task: the Simple Confidence Rating (a direct report on a numerical scale), the Quadratic Scoring Rule (a post-wagering procedure), and the Matching Probability (MP; a generalization of the no-loss gambling method). We systematically com...

Harsanyi (1955) proved that, in the context of uncertainty, social rationality and the Pareto principle impose severe constraints on the degree of priority for the worst-off that can be adopted in the social evaluation. Since then, the literature has hesitated between an ex ante approach that relaxes rationality (Diamond, 1967) and an ex post appro...

We provide possibility results on the aggregation of beliefs and tastes for Monotone, Bernoullian and Archimedian preferences of Cerreia-Vioglio, Ghirardato, Maccheroni, Mari-nacci, and Siniscalchi (2011). We propose a new axiom, Unambiguous Pareto Dominance, which requires that if the unambiguous part of individuals' preferences over a pair of act...

The most usual procedure when facing decisions in complex settings consists in consulting experts, aggregating the information they provide, and deciding on the basis of this aggregated information. We argue that such a procedure entails a substantial loss, insofar as it precludes the possibility to take into account simultaneously the decision mak...

We analyze the aggregation problem without the assumption that individuals and society have fully determined and observable preferences. More precisely, we endow individuals ans society with sets of possible von Neumann-Morgenstern utility functions over lotteries. We generalize the classical neutrality assumption to this setting and characterize t...

Fraudes sociales versus non-recours aux drotis sociaux

This introduces the symposium on inequality and risk.

Fairness issues are quite widespread in educational research. However, despite the large number of empirical studies on this topic, few question the precise way in which equality is defined and assessed. That is especially true with regards to access to higher education. In most empirical studies, it seems straightforward to consider fair any situa...

Purpose: In this paper, we analyze pregnant women’s decision towards the prenatal diagnosis of Down’s syndrome (amniocentesis); the trade-off is between doing the test which increases risk of miscarriage and not doing it with a risk of giving birth to a child suffering from Down’s syndrome. Method: We use a unique database with exact information...

Tribute to Jean-Yves Jaffray by the French Group of Decision Theory.

We study the Full Bayesian Updating rule for convex capacities. Following a route suggested by J.-Y. Jaffray [IEEE Trans. Syst. Man Cybern. 22, No. 5, 1144–1152 (1992; Zbl 0769.62001)], we define some properties one may want to impose on the updating process, and identify the classes of (convex and strictly positive) capacities that satisfy these p...

Harsanyi (1955) proved that, in the context of uncertainty, social ratio- nality and the Pareto principle impose severe constraints on the degree of priority for the worst-off that can be adopted in the social evaluation. Since then, the literature has hesitated between an ex ante approach that relaxes rationality (Diamond (1967)) and an ex post ap...

We axiomatize in the Anscombe-Aumann setting a wide class of preferences called rank-dependent additive preferences that includes most known models of decision under uncertainty as well as state dependent versions of these models. We prove that aggregation is possible and necessarily linear if and only if (society's) preferences are uncertainty neu...

This paper presents an axiomatic model of decision making under uncertainty which incorporates objective but imprecise information. Information is assumed to take the form of a probability-possibility set, that is, a set $P$ of probability measures on the state space. The decision maker is told that the true probability law lies in $P$ and is assum...

Most prominent models of economic justice (and especially those proposed by Harsanyi and Rawls) are based on the assumption that impartiality is required for making moral decisions. However, although Harsanyi and Rawls agree on that, and furthermore agree on the fact that impartiality can be obtained under appropriate conditions of ignorance, they...

The evaluation of social risk equity for alternative probability distributions over the potential sets of fatalities is analyzed axiomatically. Fishburn and Straffin [Equity considerations in public risks valuation, Operatons Research 37 (1999), 229-239] have identified a necessary and sufficient condition for two social risk distributions to be ju...

We provide a general theorem on the aggregation of preferences under uncertainty. We study, in the Anscombe-Aumann setting a wide class of preferences, that includes most known models of decision under uncertainty (and state-dependent versions of these models). We prove that aggregation is possible and necessarily linear if (society's) preferences...

The axioms that characterize the generalized Gini social evaluation orderings for one-dimensional distributions are extended to the multidimensional attributes case. A social evaluation ordering is shown to have a two-stage aggregation representation if these axioms and a separability assumption are satisfied. In the first stage, the distributions...

We develop an axiomatic approach to decision under uncertainty that explicitly takes into account the information available to the decision maker. The information is described by a set of priors and a reference prior. We define a notion of imprecision for this informational setting and show that a decision maker who is averse to information impreci...

Since the order generated by the Lorenz criterion is partial, it is a natural question to wonder how to extend this order. Most of the literature that is concerned with that question focuses on local changes in the income distribution. We follow a different approach, and define uniform α-spreads, which are global changes in the income distribution....

Ever since its introduction by Foley (1967) and Varian (1974), the notion of fairness has been one of the most extensively used notion to evaluate allocations on an ethical basis. Whereas thereis an extensive literature on the efficiency properties of allocations in economies with uncertainty the concept of an envy-free allocation has not been wide...

1 Résumé Nous considérons dans cet article leprobì eme de l'agrégation d'opinions d'ex-perts. Nous distinguons entre deux types de désaccords entre les experts. Dans un cas, la différence d'opinions tient, par exemple a l'utilisation de base de données différentes. Dans ce cas, l'agrégation linéaire des probabilités semble raisonnable. En revanche,...

This paper develops a multi-country overlapping-generations general equilibrium model to gauge the economic impacts of demographic changes in the global economy and its transmission effects on different countries. Although severe demographic pressures contribute to significantly lower real GDP per capita across several regions in the world, globali...

We provide a model of decision making under uncertainty in which the decision maker reacts to imprecision of the available data. Data is represented by a set of probability distributions. We axiomatize a decision criterion of the maxmin expected utility type, in which the revealed set of priors explicitly depends on the available data. We then char...

This paper develops a multi-country overlapping-generations general equilibrium model to gauge the economic impacts of demographic changes in the global economy and its transmission effects on different countries. Although severe demographic pressures contribute to significantly lower real GDP per capita across several regions in the world, globali...

The (generalized) Gini indices rely on the social welfare function of a decision maker who behaves in accordance with Yaari's model, with a function f that transforms frequencies. This SWF can also be represented as the weighted sum of the welfare of all the possible coalitions in the society, where the welfare of a coalition is defined as the inco...

In this paper, we provide an axiomatic characterization of social welfare functions for uncertain incomes. Our most general result is that a small number of reasonable assumptions regarding welfare orderings under uncertainty rule out pure ex ante as well as pure ex post evaluations. Any social welfare function that satisfies these axioms shouldlie...

We show that, in a two-period economy with uncertainty in the second period, if an allocation is Pareto optimal for a given set of beliefs and remains optimal when these beliefs are changed, then the set of optimal allocations of the two economies must actually coincide. We identify equivalence classes of beliefs, giving rise to the same set of Par...

It is hopeless to look for an objective measure of inequalities. Indeed, the measure of inequalities depends on citizen’s opinions about justice. It is hence necessary to explicit the ethical fundations of inequality indices. We try, in this note, to present and discuss thoroughly the consequences of the various opinions on which an inequality inde...

La recherche d'une mesure objective des inégalités, sur le modèle des mesures des grandeurs physiques est vaine : la mesure des inégalités dépend, en effet, de l'opinion des membres de la société en matière de justice distributive. Il est donc souhaitable que les opinions qui sous-tendent les mesures des inégalités soient aussi explicites que possi...

Les mesures traditionnelles des inégalités considèrent l'aversion collective à l'égard des inégalités comme un paramètre déterminé a priori. En particulier, ce paramètre est maintenu constant lorsqu'on effectue des comparaisons internationales ou intertemporelles. Nous proposons ici d'utiliser les données fiscales pour construire un indicateur d'in...

We give in this paper a formal definition of the concept of weak and strong a-polarization. We give necessary and sufficient conditions for a decision maker who respects the Lorenz order and who behaves in accordance with the expected utility model, with Yaari's dual model or with the rank-dependent expected utility model to be weakly or strongly a...

In a seminal paper, Kolm [14] introduces the principle diminishing transfer. This principle requires that a transfert from an individual with income x to one with income x - D(D > 0) has a greater impact on social welfare the lower x is. On the other hand Mehran [15] and Kakwani [11] introduced another principle, namely the principle of dual dimini...

Les mesures traditionnelles des inegalites considerent l'aversion collective a l'egard des inegalites comme un parametre determine a priori. En particulier, ce parametre est maintenu constant lorsqu'on effectue des comparaisons internationales ou intertemporelles. Nous proposons ici d'utiliser les donnees fiscales pour construire un indicateur d'in...

The purpose of this note is to build an ethical inequality index which explicitely takes into account the social attitude towards inequlaity, through the actual tax scheme. We give a rough empirical application of this subjective inequality index to the evolution of wage inequality in France over the period 1982-1992. It appears that the decision m...

We reconsider the principles of diminishing transfer (introduced by Kolm (1976)) and dual diminishing transfer (introduced by Mehran (1976)). It appears that if a Rank Depen- dent Expected Utility (RDEU) maximizer respects the principle of diminishing (resp. dual diminishing) transfer, then he behaves in accordance with the Expected Utility model (...

Mémoire de DEA : Macro-économie, modélisation et conjoncture / Paris I ; session de 1997.