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

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.

Keyphrases: Cognition, Learning, Personality, Behavioral plasticity, General plasticity, Flexibility, Sensitivity, Individual differences, Zebra finch, Sailfin molly