Personality in a group living species : social information, collective movements and social decision-making

Animals need to make constant decisions throughout their lives and to make optimal decisions individuals rely on information. Information can be obtained in two distinct ways: personal or social information. The current paradigm in the information theory use in animal ecology assumes that the decision between using either personal or social information is entirely flexible and context dependent. However, the potential link between variation in personality and information use has received little attention. In this thesis I studied the effect of personality on the use of personal and social information in barnacle geese. I show that individual barnacle geese differ consistently in boldness and that boldness affects the type of information individuals use in various different contexts: In a maze solving task, a producer scrounger game and a public information experiment I found that bold individuals use less social information compared to shy individuals, providing strong evidence that the type of information individuals prefer to use depends on their boldness level. To study the ultimate causes of variation in boldness and the relationship between boldness and social information use I used an experimental and theoretical approach. In a producer scrounger experiment I tested whether the rare personality type outperformed the common personality type which could lead by means of negative frequency dependent selection to the maintenance of variation in boldness. Parallel to that I used a genetic algorithms approach to study the co-evolution of boldness and foraging tactic use in a producer scrounger game. The experimental results as well as the genetic algorithms provided no evidence for a role of negative frequency dependent selection for the maintenance of variation in boldness. Rather, our simulations suggest that differences in selection pressures in space or time (i.e., fluctuating environments) in a social foraging game may cause variation in boldness levels between populations. In our simulations bold individuals evolved to play both producer and scrounger, whereas shy individuals remained confined to scrounging, suggesting that shy individuals have difficulties when they have to collect personal information and that this might be the explanation for the increased tendency of shy individuals to use social information. I experimentally confirmed these model predictions in an experiment in which I forced individuals in either a producer or a scrounger role. Therefore, I argue that the value of social information is higher for shy individuals as compared to bold individuals since it is more costly for shy individuals to collect personal information. This thesis challenges the current paradigm that the decision between using either personal or social information is entirely context dependent. Rather, I provide evidence that personality affects the trade off between using personal and social information. </p

The effect of exploration on the use of producer-scrounger tactics

Individuals foraging in groups can use two different tactics for obtaining food resources. Individuals can either search for food sources themselves (producing) or they can join food discoveries of others (scrounging). In this study we use a genetic algorithm in a spatially explicit producer-scrounger game to explore how individuals compromise between exploration (an important axis of animal personality) and scrounging and how characteristics of the environment affect this compromise. Agents varied in exploration and scrounging and a genetic algorithm searched for the optimal combination of exploration and scrounging. The foraging environments featured different levels of patch richness, predation and patch density. Our simulations show that under conditions of low patch densities slow exploring scroungers were favored whereas high patch density favored fast exploring individuals that either produced (at low patch richness) or scrounged (at high patch richness). In high predation environments fast exploring individuals were selected for but only at low to intermediate patch densities. Predation did not affect scrounging behavior. We did not find a divergence of exploration ‘types’ within a given environment, but there was a general association between exploration and scrounging across different environments: high rates of scrounging were observed over nearly the full spectrum of exploration values, whereas high rates of producing were only observed at high exploration values, suggesting that cases in which slow explorers start producing should be rare. Our results indicate that the spatial arrangement of food resources can affect the optimal social attraction rules between agents, the optimality of foraging tactic and the interaction between both

Quorums enable optimal pooling of independent judgements in biological systems

Collective decision-making is ubiquitous, and majority-voting and the Condorcet Jury Theorem pervade thinking about collective decision-making. Thus, it is typically assumed that majority-voting is the best possible decision mechanism, and that scenarios exist where individually-weak decision-makers should not pool information. Condorcet and its applications implicitly assume that only one kind of error can be made, yet signal detection theory shows two kinds of errors exist, ‘false positives’ and ‘false negatives’. We apply signal detection theory to collective decision-making to show that majority voting is frequently sub-optimal, and can be optimally replaced by quorum decision-making. While quorums have been proposed to resolve within-group conflicts, or manage speed-accuracy trade-offs, our analysis applies to groups with aligned interests undertaking single-shot decisions. Our results help explain the ubiquity of quorum decision-making in nature, relate the use of sub- and super-majority quorums to decision ecology, and may inform the design of artificial decision-making systems

Personality in a group living species : social information, collective movements and social decision-making

Animals need to make constant decisions throughout their lives and to make optimal decisions individuals rely on information. Information can be obtained in two distinct ways: personal or social information. The current paradigm in the information theory use in animal ecology assumes that the decision between using either personal or social information is entirely flexible and context dependent. However, the potential link between variation in personality and information use has received little attention. In this thesis I studied the effect of personality on the use of personal and social information in barnacle geese. I show that individual barnacle geese differ consistently in boldness and that boldness affects the type of information individuals use in various different contexts: In a maze solving task, a producer scrounger game and a public information experiment I found that bold individuals use less social information compared to shy individuals, providing strong evidence that the type of information individuals prefer to use depends on their boldness level. To study the ultimate causes of variation in boldness and the relationship between boldness and social information use I used an experimental and theoretical approach. In a producer scrounger experiment I tested whether the rare personality type outperformed the common personality type which could lead by means of negative frequency dependent selection to the maintenance of variation in boldness. Parallel to that I used a genetic algorithms approach to study the co-evolution of boldness and foraging tactic use in a producer scrounger game. The experimental results as well as the genetic algorithms provided no evidence for a role of negative frequency dependent selection for the maintenance of variation in boldness. Rather, our simulations suggest that differences in selection pressures in space or time (i.e., fluctuating environments) in a social foraging game may cause variation in boldness levels between populations. In our simulations bold individuals evolved to play both producer and scrounger, whereas shy individuals remained confined to scrounging, suggesting that shy individuals have difficulties when they have to collect personal information and that this might be the explanation for the increased tendency of shy individuals to use social information. I experimentally confirmed these model predictions in an experiment in which I forced individuals in either a producer or a scrounger role. Therefore, I argue that the value of social information is higher for shy individuals as compared to bold individuals since it is more costly for shy individuals to collect personal information. This thesis challenges the current paradigm that the decision between using either personal or social information is entirely context dependent. Rather, I provide evidence that personality affects the trade off between using personal and social information

Impact of sharing full versus averaged social information on social influence and estimation accuracy

International audienc

Humans use social information to adjust their quorum thresholds adaptively in a simulated predator detection experiment

Quorum sensing is used in many biological systems to increase decision accuracy. In quorum sensing, the probability that an individual adopts a behavior is a nonlinear function of the number of other individuals adopting this behavior. From an optimal decision-making perspective, individuals should adjust their quorum threshold to the particulars of the decision problem. Recent work predicts that a key factor here is the quality of social information. In particular, it is predicted that individuals should adjust their quorum thresholds such that it lies in between the average true and false positive rate of the other group members. We here test this prediction with a predator detection experiment. First, human groups observed a group of animals (projected on a white screen) in which a predator was present or absent, and each individual made an independent decision to escape or not. Second, individuals received social information on the decisions of their group members, after which individuals decided again. This social information, however, did not represent their own decisions but consisted of responses that either came from a high-performing group (i.e., many individuals detecting the predator) or from a low-performing group (i.e., few individuals detecting the predator). We found that individuals adaptively adjust their quorum threshold to the quality of the social information: when receiving social information from high-performing groups, individuals employed higher quorum thresholds than when receiving information from low-performing groups. Our study demonstrates that humans can quickly evaluate the quality of publicly available information and adaptively adjust their decision rules

Testosterone treatment can increase circulating carotenoids but does not affect yellow carotenoid-based plumage colour in blue tits

A number of mechanisms are responsible for producing the variation in natural colours, and these need not act in isolation. A recent hypothesis states that carotenoid-based coloration, in addition to carotenoid availability, is also enhanced by elevated levels of circulating testosterone (T). This has only been tested for carotenoid-coloured bare parts in birds. We performed an experimental manipulation of T levels and examined the effects on the yellow carotenoid-based breast plumage in captive yearling blue tits Cyanistes caeruleus, of which half received a diet supplemented with carotenoids. T treatment resulted in elevated plasma T compared to controls and carotenoid supplementation strongly increased plasma carotenoid levels. T treatment resulted in an additional increase in plasma carotenoid levels but only in the carotenoid-supplemented males. Carotenoid supplementation resulted in more intense breast colour (carotenoid chroma), as expected. However, there was no effect of testosterone on plumage coloration at either dietary carotenoid level. Our results suggest that T can cause an increase in plasma carotenoid concentration, but that this does not necessarily lead to improved carotenoid-based plumage coloratio