Liens entre la personnalité, la plasticité comportementale et la cognition : expériences chez le Diamant mandarin (Taeniopygia guttata) et le Molly voile (Poecilia latipinna)

Les individus diffèrent largement entre eux dans leur tendance à modifier leur comportement en réponse aux changements environnementaux, i.e., dans leur niveau de plasticité comportementale. L’ajustement du comportement requiert la perception, le traitement et éventuellement la mise à jour du comportement en fonction des changements, ce qui suggère un rôle clef de la cognition et de la personnalité dans la mise en place d’un comportement plastique. En effet, les différences individuelles de comportement (i.e., la personnalité) seraient un indicateur de la stratégie d’apprentissage des individus : les plus timides seraient lents à apprendre, sensibles aux variations subtiles dans les stimuli externes et capables de modifier rapidement leur comportement alors que les plus hardis seraient rapides à apprendre, superficiels dans leur exploration et routiniers dans l’expression de leurs comportements. Ainsi, certains individus seraient généralement plus sensibles aux conditions que les autres et devraient exprimer plus de plasticité comportementale quel que soit l’indice de la plasticité (i.e., type de mesure) utilisé. Cependant, si initialement les études ont supporté cette hypothèse, les travaux récents démontrent rarement un lien entre personnalité et cognition. De plus, il n’existe pas de preuve au niveau individuel qu’il y aurait effectivement un lien entre apprentissage, un type de plasticité développementale (i.e., changement de comportement en fonction des expériences passées) et un autre type de plasticité, la plasticité contextuelle (i.e., changement de comportement en réponse immédiate aux stimuli externes), ni que cette dernière serait répétable entre les comportements et contextes. Dans le but de mieux comprendre les mécanismes proximaux de la plasticité comportementale, j’ai déterminé dans le premier chapitre si la relation entre la personnalité et l’apprentissage pouvait expliquer la plasticité contextuelle en réponse à la présence ou l’absence d’une audience présentée sur une vidéo chez le Diamant mandarin (Taeniopygia guttata). Les résultats indiquent effectivement que les oiseaux moins néophobes étaient moins plastiques. En revanche, la néophobie n’était pas associée avec l’apprentissage suggérant que les individus plastiques ne sont pas nécessairement plus sensibles que les autres. Dans le second chapitre, j’ai tenté de mettre en évidence l’existence d’un facteur unique expliquant la plasticité contextuelle (c.-à-d. modification de la personnalité et des comportements de reproduction en fonction d’un gradient social) et l’apprentissage à renforcements inversés chez le Molly voile (Poecilia latipinna). Les individus plastiques n’étaient pas les mêmes dans tous les tests indiquant qu’exprimer de la sensibilité dans un contexte pourrait limiter l’expression de la sensibilité dans un autre contexte. Finalement, dans le troisième chapitre, j’ai démontré chez cette même espèce que l’anxiété, contrairement aux traits mesurés sur l’axe timidité-hardiesse (c.-à-d. néophobie et exploration), expliquait les scores d’apprentissage discriminant, spatial et à renforcements inversés lorsque les individus étaient familiarisés aux procédures. Dans ce cas, la timidité influence probablement l’approche des contingences environnementales alors que la réaction au stress (par exemple l’anxiété) influencerait la sensibilité permettant de répondre à ces contingences. Différentes étapes de l’apprentissage sont donc associées avec différents traits de personnalité. Ces résultats aident à comprendre les facteurs nécessaires à l’expression de la plasticité et mettent en évidence l’existence potentielle de pressions de sélection conflictuelles agissant sur les différentes étapes requises pour l’ajustement aux changements environnementaux.Individuals differ widely among each other in their tendency to modify their behavior in response to environmental changes, (i.e., in their behavioral plasticity). The adjustment of the behavior requires the perception, treatment and possibly updating of behavior as a function of change, which suggests a key role of cognition and personality in the expression of plasticity. Indeed, individual differences in behavior (i.e., personality) would be an indicator of the learning strategy of individuals: shy individuals would be slow to learn, sensitive to subtle variations in external stimuli, and able to change their behavior quickly, while the bold ones would be quick to learn, superficial in their exploration and prone to routine. Thus, some individuals would generally be more responsive to the conditions than others and should express more behavioral plasticity regardless of the proxy used. However, while studies, initially, supported this hypothesis, recent work rarely demonstrates a link between personality and cognition. Moreover, there is no evidence at the individual level that learning, a type of developmental plasticity (i.e., changes in behavior as a function of experiences that occurred in the past) and another type of plasticity, contextual plasticity (i.e., changes in behavior that occurred as an immediate response to external stimuli) would be linked, nor that plasticity would be repeatable across behaviors and contexts. In order to better understand the proximal mechanisms of behavioral plasticity, I investigated in the first chapter whether the relationship between personality and learning could explain contextual plasticity in response to the presence and absence of an audience displayed on video recordings in Zebra finches (Taeniopygia guttata). The results indicate that less neophobic birds were less plastic. In contrast, neophobia was not associated with learning suggesting that plastic individuals are not necessarily more sensitive than others. In the second chapter, I tried to highlight the existence of a single factor explaining contextual plasticity (in personality traits and mating behaviors measured across social gradients) and reversal learning in Sailfin mollies (Poecilia latipinna). Plastic individuals were not the same in all tests indicating that expressing sensitivity in one context might limit the expression of sensitivity in another context. Finally, in the third chapter, I demonstrated in this same species that anxiety, contrary to the personality traits from the shyness-boldness axis (i.e., neophobia and exploration), explained individuals’ performances in discriminant, spatial and reversal learning tasks when individuals were extensively familiarized with the procedures. Thus, shyness probably influences the time required to contact the environmental contingencies, whereas stress vulnerability (i.e., anxiety) would affect individuals’ sensitivity in response to them. Different steps of learning are therefore associated with different personality traits. These results help to understand the factors necessary for the expression of plasticity and highlight the potential existence of conflicting selection pressures acting on the different steps required for an individual to adjust its behavior to environmental conditions

Are some individuals generally more behaviorally plastic than others? An experiment with sailfin mollies

Individuals within the same population generally differ among each other not only in their behavioral traits but also in their level of behavioral plasticity (i.e., in their propensity to modify their behavior in response to changing conditions). If the proximate factors underlying individual differences in behavioral plasticity were the same for any measure of plasticity, as commonly assumed, one would expect plasticity to be repeatable across behaviors and contexts. However, this assumption remains largely untested. Here, we conducted an experiment with sailfin mollies (Poecilia latipinna) whose behavioral plasticity was estimated both as the change in their personality traits or mating behavior across a social gradient and using their performance on a reversal-learning task. We found that the correlations between pairwise measures of plasticity were weak and non-significant, thus indicating that the most plastic individuals were not the same in all the tests. This finding might arise because either individuals adjust the magnitude of their behavioral responses depending on the benefits of plasticity, and/or individuals expressing high behavioral plasticity in one context are limited by neural and/or physiological constraints in the amount of plasticity they can express in other contexts. Because the repeatability of behavioral plasticity may have important evolutionary consequences, additional studies are needed to assess the importance of trade-offs between conflicting selection pressures on the maintenance of intra-individual variation in behavioral plasticity

Data from: Does personality affect the ability of individuals to track and respond to changing conditions?

One possibility for why individual differences in behavioral plasticity are frequently associated with differences in personality might be that variation in personality is functionally related to variation in cognition. Evidence supporting a link between personality and cognition, however, is still limited and contradictory. In this study, we then conducted a laboratory experiment with zebra finches (Taeniopygia guttata) aimed at examining the role of cognition in shaping individual differences in contextual plasticity (i.e., plasticity in behavior between contexts). Specifically, we measured neophobia by quantifying the latency of the birds to eat near a novel object in two different environments across a social gradient and assessed their learning performance on two discriminant tasks and a reversal task. In agreement with our expectation, we found that less neophobic individuals were less plastic in their responses compared to more neophobic ones. Less neophobic individuals were also faster to reach the learning criterion but only in the less difficult discriminant task they performed first. On the contrary, although we found evidence for individual consistency in learning performances, differences among individuals in the number of trials needed to pass the task in both the more difficult discriminant and reversal tasks were not associated with individual differences in neophobia. Thus, our findings indicate that individual differences in contextual plasticity do not necessarily result from some individuals being more sensitive to environmental changes. Instead, we suggest that differences among individuals in their level of plasticity might result from differences in the number of suitable habitats they may occupy

Male foraging efficiency, but not male problem-solving performance, influences female mating preferences in zebra finches

Experimental evidence suggests that females would prefer males with better cognitive abilities as mates. However, little is known about the traits reflecting enhanced cognitive skills on which females might base their mate-choice decisions. In particular, it has been suggested that male foraging performance could be used as an indicator of cognitive capacity, but convincing evidence for this hypothesis is still lacking. In the present study, we investigated whether female zebra finches (Taeniopygia guttata) modify their mating preferences after having observed the performance of males on a problem-solving task. Specifically, we measured the females’ preferences between two males once before and once after an observation period, during which their initially preferred male was incapable of solving the task contrary to their initially less-preferred male. We also conducted a control treatment to test whether the shift in female preferences was attributable to differences between the two stimulus males in their foraging efficiency. Finally, we assessed each bird’s performance in a color associative task to check whether females can discriminate among males based on their learning speed. We found that females significantly increased their preference toward the most efficient male in both treatments. Yet, there was no difference between the two treatments and we found no evidence that females assess male cognitive ability indirectly via morphological traits. Thus, our results suggest that females would not use the males’ problem-solving performance as an indicator of general cognitive ability to gain indirect fitness benefits (i.e., good genes) but rather to assess their foraging efficiency and gain direct benefits

Data used for the stepwise regression analyses

Data used for the stepwise regression analyse

Data used for the linear mixed effects analyses

Data used for the linear mixed effects analyse

Are some individuals generally more behaviorally plastic than others? An experiment with sailfin mollies

Reversal learning, personality and mating tactic scores measured in male sailfin mollies <br

Experimental investigation of performances enhancement in hot carrier solar cells: improvements and perspectives (Conference Presentation)

International audienceIn single junction solar cells a large part of the incident energy ends up as heat which limits their maximum achievable efficiency. Thus the achievement of maximum power conversion efficiencies relies on complex multijunction devices. Here we show the possibility to harvest the available solar energy using hot carrier devices and evidence a positive contribution of the hot carrier effect on photovoltaic performances. We investigated a semiconductor heterostructure based on a single InGaAsP quantum well using quantitative optoelectrical characterization, especially luminance measurements. The quantitative thermodynamic study of the hot carrier population allows us to discuss the hot carrier contribution to the solar cell performance. We demonstrate that voltage and current are enhanced due to the presence of the hot carrier population in the quantum well. These experimental results substantiate the potential of increasing photovoltaic performances in the hot carrier regime. Moreover, by developing a suitable analytic theoretical framework, we show how to obtain separate (hot) temperatures of electrons and holes from photoluminescence spectra analysis. The individual thermalization coefficients of each carrier type are also discussed. The method developed in this article paves the way towards the design of new energy harvesting devices and to the development of advanced characterization tools. Finaly, to increase the PV performance enhancement and reduce the concentration factor, an optimize design is investigated