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- PublicationAccès libreLong‐term memory retention in a wild fish species “Labroides dimidiatus” eleven months after an aversive eventMemory is essential to enhance future survival and reproduction as it helps in storing and retrieving useful information to solve particular environmental problems. However, we lack quantitative evidence on how far animals in the wild can maintain given information for extended periods without reinforcement. Here, we document correlative evidence of cleaner fish Labroides dimidiatus remembering being caught in a barrier net for up to 11 months. In 2015, about 60% of cleaners from one large isolated reef had been used for laboratory experiments and then returned to their site of capture. Eleven months later, 50% of cleaners at the same site showed an unusual hiding response to the placement of the barrier net, in contrast to three control sites where no cleaners had been caught during the last 2 years. The results suggest that a single highly aversive event (i.e., being caught in a barrier net) resulted in cleaners storing long‐term crucial information that allowed them to avoid being caught again. Our results further our knowledge of fish cognitive capacities and long‐term memory retention.
- PublicationMétadonnées seulementEndogenous oxytocin predicts helping and conversation as a function of group membershipHumans cooperate with unrelated individuals to an extent that far outstrips any other species. We also display extreme variation in decisions about whether to cooperate or not, and the mechanisms driving this variation remain an open question across the behavioural sciences. One candidate mechanism underlying this variation in cooperation is the evolutionary ancient neurohormone oxytocin (OT). As current research focuses on artificial administration of OT in asocial tasks, little is known about how the hormone in its naturally occurring state actually impacts behaviour in social interactions. Using a new optimal foraging paradigm, the ‘egg hunt’, we assessed the association of endogenous OT with helping behaviour and conversation. We manipulated players' group membership relative to each other prior to an egg hunt, during which they had repeated opportunities to spontaneously help each other. Results show that endogenous baseline OT predicted helping and conversation type, but crucially as a function of group membership. Higher baseline OT predicted increased helping but only between in-group players, as well as decreased discussion about individuals’ goals between in-group players but conversely more of such discussion between out-group players. Subsequently, behaviour but not conversation during the hunt predicted change in OT, in that out-group members who did not help showed a decrease in OT from baseline levels. In sum, endogenous OT predicts helping behaviour and conversation, importantly as a function of group membership, and this effect occurs in parallel to uniquely human cognitive processes.
- PublicationAccès libreThe language of cooperation: shared intentionality drives variation in helping as a function of group membershipWhile we know that the degree to which humans are able to cooperate is unrivalled by other species, the variation humans actually display in their cooperative behaviour has yet to be fully explained. This may be because research based on experimental game-theoretical studies neglects fundamental aspects of human sociality and psychology, namely social interaction and language. Using a newoptimal foraging game loosely modelled on the prisoner’s dilemma, the Egg Hunt, we categorized players as either in-group or out-group to each other and studied their spontaneous language usage while they made interactive, potentially cooperative decisions. Both shared group membership and the possibility to talk led to increased cooperation and overall success in the hunt. Notably, analysis of players’ conversations showed that in-group members engaged more in shared intentionality, the human ability to both mentally represent and then adopt another’s goal, whereas out-group members discussed individual goals more. Females also helped more and displayed more shared intentionality in discussions than males. Crucially, we show that shared intentionality was the mechanism driving the increase in helping between in-group players over out-group players at a cost to themselves. By studying spontaneous language during social interactions and isolating shared intentionality as the mechanism underlying successful cooperation, the current results point to a probable psychological source of the variation in cooperation humans display.
- PublicationMétadonnées seulementWhy mutual helping in most natural systems is neither conflict-free nor based on maximal conflictMutual helping for direct benefits can be explained by various game theoretical models, which differ mainly in terms of the underlying conflict of interest between two partners. Conflict is minimal if helping is self-serving and the partner benefits as a by-product. In contrast, conflict is maximal if partners are in a prisoner's dilemma with both having the pay-off-dominant option of not returning the other's investment. Here, we provide evolutionary and ecological arguments for why these two extremes are often unstable under natural conditions and propose that interactions with intermediate levels of conflict are frequent evolutionary endpoints. We argue that by-product helping is prone to becoming an asymmetric investment game since even small variation in by-product benefits will lead to the evolution of partner choice, leading to investments by the chosen class. Second, iterated prisoner's dilemmas tend to take place in stable social groups where the fitness of partners is interdependent, with the effect that a certain level of helping is self-serving. In sum, intermediate levels of mutual helping are expected in nature, while efficient partner monitoring may allow reaching higher levels.
- PublicationMétadonnées seulementNo scope for social modulation of steroid levels in a year-round territorial damselfish
- PublicationMétadonnées seulementFish choose appropriately when and with whom to collaborate(2014)
;Vail, Alexander L ;Manica, Andrea
- PublicationMétadonnées seulementDifferences in Diet Between Six Neighbouring Groups of Vervet Monkeys(2014)
;Tournier, Emilie ;Tournier, Virginia ;Waal, Erica ;Barrett, Alan ;Brown, Leslie
- PublicationMétadonnées seulementReferential gestures in fish collaborative hunting(2013)
;Vail, Alexander L. ;Manica, Andrea
- PublicationMétadonnées seulementThird-Party Ranks Knowledge in Wild Vervet Monkeys (Chlorocebus aethiops pygerythrus)
- PublicationMétadonnées seulementNegotiations over Grooming in Wild Vervet Monkeys (Chlorocebus pygerythrus)