Toward the understanding of TIR-NB-LRR–mediated immunity; study of the AvrRps4 recognition model in Arabidopsis

The recognition of pathogen–secreted effectors is a major component of plant innate immunity and is mainly mediated by NB-LRR resistance (R) proteins. However, the mechanisms by which NB-LRR proteins recognize effectors and induce downstream signaling events are poorly known. This PhD work focused on the characterization of TIR-NB-LRR–mediated immnunity in plants. In Arabidopsis, two TIR-NB-LRR encoding R genes, RRS1 and RPS4, are in a head-to-head arrangement on chromosome 5. They interact to confer recognition to AvrRps4 and (with the right allele of RRS1) PopP2, two bacterial effectors, from Pseudomonas syringae and Ralstonia solanacearum respectively. To dissect AvrRps4–triggered immunity, I focused on the RRS1– and RPS4–independent AvrRps4 recognition (RRIR) observed in the Ws-2 and Col-0 Arabidopsis accessions. I map-based cloned another pair of R genes, RRS1B and RPS4B, genetically linked and highly similar to RRS1-RPS4, responsible for the RRIR. Interestingly, RRS1B-RPS4B recognizes AvrRps4 but not PopP2. Using domain swap experiments, I demonstrated that RRS1 exons 5, 6 and 7 specify PopP2 recognition. My data suggest that AvrRps4 and PopP2 interact directly with RRS1 and RRS1B. However, the exact mechanism by which these effectors activate TIR-NB-LRR R proteins remains to be determined. Overexpressing the N-terminal domain of RPS4, RPS4TIR+80, activates cell death in plants and I demonstrated that it requires a nuclear localization. Similarly, the C-terminal part of RPS4B comprises a nuclear localization signal and is required for RRS1B-RPS4B–dependent AvrRps4 recognition. Interestingly, RPS4TIR+80–mediated cell death can be suppressed by co-expressing RRS1TIR. Using a proteomic approach, I showed that TIR domains and full length RRS1, RPS4, RRS1B and RPS4B can associate in planta forming distinct heterodimers. However, I showed that, despite their homologies, these R proteins only function with their respective pair partner for effector recognition and/or downstream signaling activation

Wishful thinking: a group approach

This study attempts to understand the wishful thinking effect through a group approach. We build a group decision making model that tries to explain how a group dynamic can lead the group to interpret and recall data so that they correspond to more favorable beliefs about the group future prospects. Group members have to take one single common decision determining the group effort level in a joint production. We find that (a) An agent's incentive to enter into denial when others are in denial is higher than an agent's incentive to enter into denial when he is alone; (b) An agent's incentive to enter into denial when others are realist is lower than an agent's incentive to enter into denial when he is alone; (c) An agent's incentive to enter into denial increases with the riskiness of the project; (d) the presence of a leader can either increase or decrease the incentive to enter into denial depending on assumptions made on costs. We build an experimental protocol allowing to try to test the previous model and validate or not its predictions.Cette étude tente de comprendre l'effet la pensée désidérative par le biais d'une approche de groupe. Nous construisons un modèle de prise de décision de groupe qui tente d'expliquer comment une dynamique de groupe peut amener le groupe à interpréter et à se rappeler des données de manière à ce qu'elles correspondent à des croyances plus favorables à l'avenir du groupe. Les membres du groupe doivent prendre une seule décision commune déterminant le niveau d'effort du groupe dans une production commune. Nous constatons que (a) l'incitation d'un agent à entrer dans le déni lorsque les autres sont dans le déni est plus élevée que l'incitation d'un agent à entrer dans le déni lorsqu'il est seul ; (b) l'incitation d'un agent à entrer dans le déni lorsque les autres sont réalistes est plus faible que l'incitation d'un agent à entrer dans le déni lorsqu'il est seul ; (c) l'incitation d'un agent à entrer dans le déni augmente avec le degré de risque du projet ; (d) la présence d'un leader peut soit augmenter soit diminuer l'incitation à entrer dans le déni selon les hypothèses faites sur les coûts. Nous construisons un protocole expérimental permettant d'essayer de tester le modèle précédent et de valider ou non ses prédictions

The causal effect of a health treatment on beliefs, stated preferences and memories

The paper estimates the causal effect of a health treatment on patients’ beliefs, preferences and memories about the treatment. It exploits a natural experiment which occurred in the United Kingdom during the COVID-19 vaccination campaign. UK residents could choose to opt into the vaccination program, but not which vaccine they received. The assignment to a vaccine offered little objective information for learning about its qualities, but triggered strong psychological demand for reassuring beliefs. We surveyed a sample of UK residents about their beliefs on the different COVID-19 vaccines before and after receiving their jab. Before vaccination, individuals exhibit similar prior beliefs and stated preferences about the different vaccines. After vaccination, however, they update their beliefs overly optimistically about the safety and effectiveness of the vaccine they received, state that they would have chosen it if they could, and have distorted memories about their past beliefs. These results cannot be explained by conventional experience effects. At the aggregated level, they show that random assignment to a health treatment predicts a polarization of opinions about its quality. At the individual level, these findings provide evidence in line with the predictions of motivated beliefs and over-inference from weak signals in a real-world health setting

The HEV Ventilator

HEV is a low-cost, versatile, high-quality ventilator, which has been designed in response to the COVID-19 pandemic. The ventilator is intended to be used both in and out of hospital intensive care units, and for both invasive and non-invasive ventilation. The hardware can be complemented with an external turbine for use in regions where compressed air supplies are not reliably available. The standard modes provided include PC-A/C(Pressure Assist Control),PC-A/C-PRVC(Pressure Regulated Volume Control), PC-PSV (Pressure Support Ventilation) and CPAP (Continuous Positive airway pressure). HEV is designed to support remote training and post market surveillance via a web interface and data logging to complement the standard touch screen operation, making it suitable for a wide range of geographical deployment. The HEV design places emphasis on the quality of the pressure curves and the reactivity of the trigger, delivering a global performance which will be applicable to ventilator needs beyond theCOVID-19 pandemic. This article describes the conceptual design and presents the prototype units together with their performance evaluation.Comment: 34 pages, 18 figures, Extended version of the article submitted to PNA

Wishful thinking: a group approach

This study attempts to understand the wishful thinking effect through a group approach. We build a group decision making model that tries to explain how a group dynamic can lead the group to interpret and recall data so that they correspond to more favorable beliefs about the group future prospects. Group members have to take one single common decision determining the group effort level in a joint production. We find that (a) An agent's incentive to enter into denial when others are in denial is higher than an agent's incentive to enter into denial when he is alone; (b) An agent's incentive to enter into denial when others are realist is lower than an agent's incentive to enter into denial when he is alone; (c) An agent's incentive to enter into denial increases with the riskiness of the project; (d) the presence of a leader can either increase or decrease the incentive to enter into denial depending on assumptions made on costs. We build an experimental protocol allowing to try to test the previous model and validate or not its predictions.Cette étude tente de comprendre l'effet la pensée désidérative par le biais d'une approche de groupe. Nous construisons un modèle de prise de décision de groupe qui tente d'expliquer comment une dynamique de groupe peut amener le groupe à interpréter et à se rappeler des données de manière à ce qu'elles correspondent à des croyances plus favorables à l'avenir du groupe. Les membres du groupe doivent prendre une seule décision commune déterminant le niveau d'effort du groupe dans une production commune. Nous constatons que (a) l'incitation d'un agent à entrer dans le déni lorsque les autres sont dans le déni est plus élevée que l'incitation d'un agent à entrer dans le déni lorsqu'il est seul ; (b) l'incitation d'un agent à entrer dans le déni lorsque les autres sont réalistes est plus faible que l'incitation d'un agent à entrer dans le déni lorsqu'il est seul ; (c) l'incitation d'un agent à entrer dans le déni augmente avec le degré de risque du projet ; (d) la présence d'un leader peut soit augmenter soit diminuer l'incitation à entrer dans le déni selon les hypothèses faites sur les coûts. Nous construisons un protocole expérimental permettant d'essayer de tester le modèle précédent et de valider ou non ses prédictions

Essais en économie comportementale sur la mémoire motivée

This thesis investigates whether individuals use their memory as a self-deceptive strategy to sustain motivated beliefs. It tests experimentally the existence and strength of memory manipulation in three economically relevant contexts: social interactions, individual performance and unethical decisions.Chapter one investigates whether people retrieve their memory self-servingly in social encounters. Do individuals forget the consequences of their actions on others? If so, does it depend on the nature (e.g. selfish or altruistic) of the action? Our results identify a causal effect of the responsibility of pro-social decisions on selective recalls. In contrast, there is no clear evidence of biased memory errors. Chapter two disentangles between two driving forces that have been proposed as explanations of memory failures for self-relevant information: self-enhancement and mood-congruency. We provide a controlled environment where the two theories predict different outcomes. Our results provide support for the existence and relative dominance of self-enhancing memory over mood-congruent memory and thereby underline the importance of motivational factors in the formation of optimistic beliefs about the self.Chapter three investigates the relative role of affect and strategic reasoning in motivated memory, with an application in the domain of unethical behavior. We study whether individuals manipulate the memory of past dishonest choices, and whether they use their memory as an instrument to justify future decisions. We find that hedonic considerations are not sufficient to trigger memory manipulation. When forgetting serves as a justification to not engage in future morally responsible behavior, however, individuals do motivate their memory.Together, these results show that memory errors in economic contexts can result from cognitive impairment but also from memory distortion motivated by the willingness to protect one's self-image and future choices.Cette thèse cherche à déterminer si les individus manipulent leur mémoire pour oublier certaines informations qui menacent leurs croyances. Elle teste expérimentalement l’existence et la force de la mémoire motivée dans trois contextes économiquement pertinents : les préférences sociales, la performance individuelle et les décisions malhonnêtes. Le chapitre 1 examine si les individus font preuve de mémoire motivée dans les interactions sociales. Les individus oublient-ils les conséquences de leurs actes sur autrui ? Le cas échéant, cela dépend-il de la nature (par exemple, égoïste ou altruiste) de leurs actes ? Nos résultats confirment la sélectivité des souvenirs. Les individus se souviennent mieux des conséquences de leurs actions sur autrui lorsqu'ils ont été généreux que lorsqu'ils ont été égoïstes. En revanche, la direction et la magnitude des erreurs de mémoire ne diffèrent pas selon la nature des choix. Le chapitre 2 démêle deux mécanismes identifiés comme explications possibles de l'existence de mémoire sélective concernant les performances individuelles : l'auto-renforcement et la congruence de l'humeur. Nous testons l'existence de mémoire motivée dans un environnement contrôlé où les deux théories offrent des prédictions divergentes. Nos résultats supportent l'existence et la dominance relative de l'effet d'auto-renforcement par rapport à la congruence de l'humeur, et soulignent ainsi l'importance des facteurs motivationnels plutôt qu'affectifs dans la formation de croyances motivées.Le chapitre 3 examine si les individus oublient leurs comportements malhonnêtes, non seulement pour des motifs hédoniques mais aussi pour des raisons stratégiques, lorsque l'oubli sert à justifier une décision future. Nous trouvons que les considérations hédoniques seules ne sont pas suffisantes pour déclencher une manipulation de la mémoire. En revanche, lorsqu'oublier sert d'excuse pour ne pas avoir à s'engager dans un comportement moralement responsable, les individus manipulent leur mémoire. Ces résultats montrent que les erreurs de mémoire dans les contextes économiques peuvent résulter d'une déficience cognitive mais aussi d'une mémoire motivée par la volonté de ne pas avoir à se confronter à des informations pouvant nuire à l'image de soi et remettre en cause ses choix futurs

Motivated Skepticism

We experimentally study how individuals read strategically-transmitted information when they have preferences over what they will learn. Subjects play disclosure games in which Receivers should interpret messages skeptically. We vary whether the state that Senders communicate about is ego-relevant or neutral for Receivers, and whether skeptical beliefs are aligned or not with what Receivers prefer believing. Skepticism is lower when skeptical beliefs are self-threatening than in neutral settings. When skeptical beliefs are self-serving, skepticism is not enhanced compared to neutral settings. These results demonstrate that individuals' exercise of skepticism depends on the conclusions of skeptical inferences