How social network structure affects decision-making in Drosophila melanogaster

Animals use a number of different mechanisms to acquire crucial information. During social encounters, animals can pass information from one to another but, ideally, they would only use information that benefits survival and reproduction. Therefore, individuals need to be able to determine the value of the information they receive. One cue can come from the behaviour of other individuals that are already using the information. Using a previous extended dataset, we studied how individual decision-making is influenced by the behaviour of conspecifics in Drosophila melanogaster. We analysed how uninformed flies acquire and later use information about oviposition site choice they learn from informed flies. Our results suggest that uninformed flies adjust their future choices based on how coordinated the behaviours of the informed individuals they encounter are. Following social interaction, uninformed flies tended either to collectively follow the choice of the informed flies or to avoid it. Using social network analysis, we show that this selective information use seems to be based on the level of homogeneity of the social network. In particular, we found that the variance of individual centrality parameters among informed flies was lower in the case of a ‘follow’ outcome compared with the case of an ‘avoid’ outcome.     

Wood warblers copy settlement decisions of poor quality conspecifics: support for the tradeoff between the benefit of social information use and competition avoidance

Social information use in songbird habitat selection commonly involves a conspecific attraction strategy. Individuals copy the breeding‐site choices of conspecifics, that is, bias their own settlement decisions towards sites (tracts of spatially limited habitat with similar structure) already occupied by others. In order to be adaptive, social information use has to be discriminative. Especially the decisions of good quality individuals, i.e. measuring high at observable fitness correlates, should be copied more frequently than those of poor quality individuals. It is unknown, however, whether songbirds discriminatively use conspecific presence by evaluating the quality of information providers in habitat selection. We experimentally tested whether wood warblers Phylloscopus sibilatrix selectively copied settlement decisions of conspecifics in relation to the quality of observed individuals. We also tested whether the use of social cues was influenced by the population density at a particular site in the preceding year. We found that wood warblers selectively used intraspecific social information, but in a pattern opposite to that expected based on existing hypotheses. Wood warblers copied breeding‐site choices of poor quality conspecifics and despite temporary attraction to sites where the presence of good quality individuals was simulated, they did not ultimately settle near these individuals. Population density in the preceding year did not influence settlement patterns. We argue that when making settlement decisions, wood warblers assessed the expected level of local intraspecific competition and selectively copied breeding‐site choices of conspecifics or refused to settle, depending on competitive abilities of observed individuals. This adds a novel aspect to the patterns and processes of social information use proposed thus far, and provides support for the predicted negative effect of intraspecific competition on benefit of information. Moreover, it seems that habitat selection in wood warblers is a complex decision‐making process, in which initial decisions are adjusted after acquiring more accurate information. Synthesis Social information use in songbird habitat selection commonly involves copying the breeding‐site choices of conspecifics (so‐called conspecific attraction). To be adaptive, this strategy has to be discriminative, but almost no empirical studies have tested this assertion. Our study shows that birds may selectively use social information by copying settlement decisions of poor quality conspecifics, but avoid settling near good quality individuals, likely because of their high competitive abilities. This decision‐making pattern supports the predicted, yet not experimentally tested, tradeoff between information value and cost of competition in social information use. Our study highlights also that the use of social cues in settlement decisions may be both positively and negatively biased.     

Bargaining babblers: vocal negotiation of cooperative behaviour in a social bird

Wherever individuals perform cooperative behaviours, each should be selected to adjust their own current contributions in relation to the likely future contributions of their collaborators. Here, we use the sentinel system of pied babblers (Turdoides bicolor) to show that individuals anticipate contributions by group mates, adjusting their own contribution in response to information about internal state broadcast by others. Specifically, we show that (i) short-term changes in state influence contributions to a cooperative behaviour, (ii) individuals communicate short-term changes in state, and (iii) individuals use information about the state of group mates to adjust their own investment in sentinel behaviour. Our results demonstrate that individual decisions about contributions to a cooperative effort can be influenced by information about the likely future contribution of others. We suggest that similar pre-emptive adjustments based on information obtained from collaborators will be a common feature of cooperative behaviour, and may play an important role in the development of complex communication in social species.     

Information,behaviour and population dynamics

Animals must make decisions such as where and when to forage based on imperfect information about their variable world. A growing number of authors have addressed the information problem and its relation to behaviour, learning, cognition and evolution. Few studies, however, have analyzed how the quality of information available for decision making affects population growth and dynamics. Here I utilize stochastic dynamic models, statistical decision theory, and projection matrices to show how information affects patch choice and how these choices in turn affect fitness and population growth. The value of information, in terms of its impact on ?tness, depends on an organism's state and changes during the organism's life span. The relationship between a population's rate of increase and uncertainty about optimal patch choice amongst its members is concave with the positive effects of reduced uncertainty diminishing rapidly as individuals become more knowledgeable about their environment. The implications of these results for understanding populations and communities of interacting species are discussed.     

Density, social information, and space use in the common lizard (Lacerta vivipara)

Socially acquired information is widespread in the animal kingdom.Many individuals make behavioral decisions based on such socialinformation. In particular, individuals may decide to leaveor select their habitat based on social information. Few studieshave investigated the role of density-related information, apotential social cue about habitat quality in dispersal. Here,we tested for the possibility that the phenotype of intrudercommon lizards (Lacerta vivipara) may inadvertently carry informationabout their natal population density. We found that such informationuse is likely. The behavior of focal lizard was influenced bythe natal population density of the intruder it was interactingwith. This suggests that individuals may use the behavior ofothers to acquire appropriate information about surroundingsand to base spatial decisions on this information. Density-relatedinformation may then affect individual movement decisions andthus metapopulation dynamics.     

Individual-level personality influences social foraging and collective behaviour in wild birds

There is increasing evidence that animal groups can maintain coordinated behaviour and make collective decisions based on simple interaction rules. Effective collective action may be further facilitated by individual variation within groups, particularly through leader–follower polymorphisms. Recent studies have suggested that individual-level personality traits influence the degree to which individuals use social information, are attracted to conspecifics, or act as leaders/followers. However, evidence is equivocal and largely limited to laboratory studies. We use an automated data-collection system to conduct an experiment testing the relationship between personality and collective decision-making in the wild. First, we report that foraging flocks of great tits (Parus major) show strikingly synchronous behaviour. A predictive model of collective decision-making replicates patterns well, suggesting simple interaction rules are sufficient to explain the observed social behaviour. Second, within groups, individuals with more reactive personalities behave more collectively, moving to within-flock areas of higher density. By contrast, proactive individuals tend to move to and feed at spatial periphery of flocks. Finally, comparing alternative simulations of flocking with empirical data, we demonstrate that variation in personality promotes within-patch movement while maintaining group cohesion. Our results illustrate the importance of incorporating individual variability in models of social behaviour.     

Counterfactual choice and learning in a neural network centered on human lateral frontopolar cortex

Decision making and learning in a real-world context require organisms to track not only the choices they make and the outcomes that follow but also other untaken, or counterfactual, choices and their outcomes. Although the neural system responsible for tracking the value of choices actually taken is increasingly well understood, whether a neural system tracks counterfactual information is currently unclear. Using a three-alternative decision-making task, a Bayesian reinforcement-learning algorithm, and fMRI, we investigated the coding of counterfactual choices and prediction errors in the human brain. Rather than representing evidence favoring multiple counterfactual choices, lateral frontal polar cortex (lFPC), dorsomedial frontal cortex (DMFC), and posteromedial cortex (PMC) encode the reward-based evidence favoring the best counterfactual option at future decisions. In addition to encoding counterfactual reward expectations, the network carries a signal for learning about counterfactual options when feedback is available-a counterfactual prediction error. Unlike other brain regions that have been associated with the processing of counterfactual outcomes, counterfactual prediction errors within the identified network cannot be related to regret theory. Furthermore, individual variation in counterfactual choice-related activity and prediction error-related activity, respectively, predicts variation in the propensity to switch to profitable choices in the future and the ability to learn from hypothetical feedback. Taken together, these data provide both neural and behavioral evidence to support the existence of a previously unidentified neural system responsible for tracking both counterfactual choice options and their outcomes.     

Group decision making in fission-fusion societies: evidence from two-field experiments in Bechstein's bats

Group decisions are required when group coordination is beneficial, but individuals can choose between alternatives. Despite the increased interest in animal group decision making, there is a lack of experimental field studies that investigate how animals with conflicting information make group decisions. In particular, no field studies have considered the influence of fission-fusion behaviour (temporary splitting into subgroups) on group decisions. We studied group decision making in two wild Bechstein's bat colonies, which are fission-fusion societies of stable individual composition. Since they frequently switch communal roosts, colony members must regularly make group decisions over where to roost. In the two-field experiments, we provided marked individuals with conflicting information about the suitability of potential roosts. We investigated whether conflicting information led to group decisions that followed a 'unanimous' or a 'majority' rule, or increased colony fission. Individual behaviour suggests that bats considered both their own information and the behaviour of others when deciding where to roost. Group decisions about communal roosts reflected the information available to a majority of the bats roosting together, but conflicting information led to an increased fission in one colony. Our results suggest that fission-fusion societies allow individuals to avoid majority decisions that are not in their favour.     

Media and breastfeeding: Friend or foe?

This short essay examines infant formula marketing and information sources for their representation of "choice" in the infant feeding context, and finds that while providing information about breast and bottle feeding, infant formula manufacturers focus on mothers' feelings and intuition rather than knowledge in making decisions. In addition, the essay considers how "choice" operates in the history of reproductive rights, shifting the discourse from a rights-based set of arguments to one based on a consumerist mentality. Utilizing the work of historian Rickie Solinger and a 2007 paper for the National Bureau of Labor Statistics, I argue that the structure of market work, and not abstract maternal decision making, determine mothers' choices and practices concerning infant feeding. For true freedoms for mothers to be achieved, freedoms that would include greater social provisions for mothers, our culture will have to confront how structural constraints make breastfeeding difficult, as well as how the concept of choice divides mothers into those who make good choices and those who do not.     

How rhesus monkey mothers and infants keep in touch when infants are at risk from social companions

Ten-to 17-week-old rhesus monkey infants that received hits from companions other than their mother at high rates (relative to their rates of involvement in playful social encounters with those companions) tended to be members of mother-infant dyads that were vigilant. Criteria of vigilance were frequent contacts between mother and infant during the first 5 sec of the infants’ social encounters and/or a bias of mother-infant contacts toward that time. Infants that received few hits per encounter came from both vigilant and nonvigilant dyads. When analyzed alone, mothers’ rates showed the same trends. High levels of vigilance tended to reduce infants’rates of making social contacts. Maternal social rank and other measures of the infants’ social involvement were not correlated with vigilance. There is no evidence that mothers and infants were in conflict with each other about interrupting the infants’ encounters. Understanding vigilance becomes important whenever vigilant activity conflicts with other activities. Special problems arise because decisions about vigilance levels require judgments of risk based on the kinds of events that occur only rarely if vigilance is effective. A model providing a framework for studies of vigilance against the risks of infants’ social activities was developed. It recognizes that (1) risk-reducing vigilant behavior can conflict with acquiring information about risk; (2) in social situations where reliable estimates of risk are impossible, individuals might follow rules of thumb (e.g., be restrictive) rather than modify behavior moment by moment according to the current situation;and (3) at the dyad’s optimum balance between vigilance for the current infant and investment in subsequent off-spring, the infant will not be totally protected, so that while dyads at higher risks are more vigilant, the risks are also realized to a greater extent (e.g., itin terms of the number of hits received per encounter).     

Information flow,opinion polling and collective intelligence in house-hunting social insects

The sharing and collective processing of information by certain insect societies is one of the reasons that they warrant the superlative epithet ''super-organisms'' (Franks 1989, Am. Sci. 77, 138-145). We describe a detailed experimental and mathematical analysis of information exchange and decision-making in, arguably, the most difficult collective choices that social insects face: namely, house hunting by complete societies. The key issue is how can a complete colony select the single best nest-site among several alternatives? Individual scouts respond to the diverse information they have personally obtained about the quality of a potential nest-site by producing a recruitment signal. The colony then deliberates over (i.e. integrates) different incoming recruitment signals associated with different potential nest-sites to achieve a well-informed collective decision. We compare this process in honeybees and in the ant Leptothorax albipennis. Notwithstanding many differences - for example, honeybee colonies have 100 times more individuals than L. albipennis colonies - there are certain similarities in the fundamental algorithms these societies appear to employ when they are house hunting. Scout honeybees use the full power of the waggle dance to inform their nest-mates about the distance and direction of a potential nest-site (and they indicate the quality of a nest-site indirectly through the vigour of their dance), and yet individual bees perhaps only rarely make direct comparisons of such sites. By contrast, scouts from L. albipennis colonies often compare nest-sites, but they cannot directly inform one another of their estimation of the quality of a potential site. Instead, they discriminate between sites by initiating recruitment sooner to better ones. Nevertheless, both species do make use of forms of opinion polling. For example, scout bees that have formerly danced for a certain site cease such advertising and monitor the dances of others at random. That is, they act without prejudice. They neither favour nor disdain dancers that advocate the site they had formerly advertised or the alternatives. Thus, in general the bees are less well informed than they would be if they systematically monitored dances for alternative sites rather than spending their time reprocessing information they already have. However, as a result of their lack of prejudice, less time overall will be wasted in endless debate among stubborn and potentially biased bees. Among the ants, the opinions of nest-mates are also pooled effectively when scouts use a threshold population of their nest-mates present in a new nest-site as a cue to switch to more rapid recruitment. Furthermore, the ants'' reluctance to begin recruiting to poor nest-sites means that more time is available for the discovery and direct comparison of alternatives. Likewise, the retirement of honeybee scouts from dancing for a given site allows more time for other scouts to find potentially better sites. Thus, both the ants and the bees have time-lags built into their decision-making systems that should facilitate a compromise between thorough surveys for good nest-sites and relatively rapid decisions. We have also been able to show that classical mathematical models can illuminate the processes by which colonies are able to achieve decisions that are relatively swift and very well informed.     

Kin selection and the evolution of social information use in animal conflict

Animals often use social information about conspecifics in making decisions about cooperation and conflict. While the importance of kin selection in the evolution of intraspecific cooperation and conflict is widely acknowledged, few studies have examined how relatedness influences the evolution of social information use. Here we specifically examine how relatedness affects the evolution of a stylised form of social information use known as eavesdropping. Eavesdropping involves individuals escalating conflicts with rivals observed to have lost their last encounter and avoiding fights with those seen to have won. We use a game theoretical model to examine how relatedness affects the evolution of eavesdropping, both when strategies are discrete and when they are continuous or mixed. We show that relatedness influences the evolution of eavesdropping, such that information use peaks at intermediate relatedness. Our study highlights the importance of considering kin selection when exploring the evolution of complex forms of information use.     

Composite collective decision-making

Individual animals are adept at making decisions and have cognitive abilities, such as memory, which allow them to hone their decisions. Social animals can also share information. This allows social animals to make adaptive group-level decisions. Both individual and collective decision-making systems also have drawbacks and limitations, and while both are well studied, the interaction between them is still poorly understood. Here, we study how individual and collective decision-making interact during ant foraging. We first gathered empirical data on memory-based foraging persistence in the ant Lasius niger. We used these data to create an agent-based model where ants may use social information (trail pheromones), private information (memories) or both to make foraging decisions. The combined use of social and private information by individuals results in greater efficiency at the group level than when either information source was used alone. The modelled ants couple consensus decision-making, allowing them to quickly exploit high-quality food sources, and combined decision-making, allowing different individuals to specialize in exploiting different resource patches. Such a composite collective decision-making system reaps the benefits of both its constituent parts. Exploiting such insights into composite collective decision-making may lead to improved decision-making algorithms.     

Shared or unshared consensus decision in macaques?

Members of a social group have to make collective decisions in order to synchronise their activities. In a shared consensus decision, all group members can take part in the decision whereas in an unshared consensus decision, one individual, usually a dominant member of the group, takes the decision for the rest of the group. It has been suggested that the type of decision-making of a species could be influenced by its social style. To investigate this further, we studied collective movements in two species with opposed social systems, the Tonkean macaque (Macaca tonkeana) and the rhesus macaque (Macaca mulatta). From our results, it appears that the decision to move is the result of the choices and actions of several individuals in both groups. However, this consensus decision involved nearly all group members in Tonkean macaques whereas dominant and old individuals took a prominent role in rhesus macaques. Thus, we suggest that Tonkean macaques display equally shared consensus decisions to move, whereas in the same context rhesus macaque exhibit partially shared consensus decisions. Such a difference in making a collective decision might be linked to the different social systems of the two studied species.     

When to use social information: the advantage of large group size in individual decision making

Correct decision making is crucial for animals to maximize foraging success and minimize predation risk. Group-living animals can make such decisions by using their own personal information or by pooling information with other group members (i.e. social information). Here, we investigate how individuals might best balance their use of personal and social information. We use a simple modelling approach in which individual decisions based upon social information are more likely to be correct when more individuals are involved and their personal information is more accurate. Our model predicts that when the personal information of group members is poor (accurate less than half the time), individuals should avoid pooling information. In contrast, when personal information is reliable (accurate at least half the time), individuals should use personal information less often and social information more often, and this effect should grow stronger in larger groups. One implication of this pattern is that social information allows less well-informed members of large groups to reach a correct decision with the same probability as more well-informed members of small groups. Thus, animals in larger groups may be able to minimize the costs of collecting personal information without impairing their ability to make correct decisions.     

Motion-guided attention promotes adaptive communications during social navigation

Animals are capable of enhanced decision making through cooperation, whereby accurate decisions can occur quickly through decentralized consensus. These interactions often depend upon reliable social cues, which can result in highly coordinated activities in uncertain environments. Yet information within a crowd may be lost in translation, generating confusion and enhancing individual risk. As quantitative data detailing animal social interactions accumulate, the mechanisms enabling individuals to rapidly and accurately process competing social cues remain unresolved. Here, we model how motion-guided attention influences the exchange of visual information during social navigation. We also compare the performance of this mechanism to the hypothesis that robust social coordination requires individuals to numerically limit their attention to a set of n-nearest neighbours. While we find that such numerically limited attention does not generate robust social navigation across ecological contexts, several notable qualities arise from selective attention to motion cues. First, individuals can instantly become a local information hub when startled into action, without requiring changes in neighbour attention level. Second, individuals can circumvent speed–accuracy trade-offs by tuning their motion thresholds. In turn, these properties enable groups to collectively dampen or amplify social information. Lastly, the minority required to sway a group''s short-term directional decisions can change substantially with social context. Our findings suggest that motion-guided attention is a fundamental and efficient mechanism underlying collaborative decision making during social navigation.     

Adaptations for social cognition in the primate brain

Studies of the factors affecting reproductive success in group-living monkeys have traditionally focused on competitive traits, like the acquisition of high dominance rank. Recent research, however, indicates that the ability to form cooperative social bonds has an equally strong effect on fitness. Two implications follow. First, strong social bonds make individuals'' fitness interdependent and the ‘free-rider’ problem disappears. Second, individuals must make adaptive choices that balance competition and cooperation—often with the same partners. The proximate mechanisms underlying these behaviours are only just beginning to be understood. Recent results from cognitive and systems neuroscience provide us some evidence that many social and non-social decisions are mediated ultimately by abstract, domain-general neural mechanisms. However, other populations of neurons in the orbitofrontal cortex, striatum, amygdala and parietal cortex specifically encode the type, importance and value of social information. Whether these specialized populations of neurons arise by selection or through developmental plasticity in response to the challenges of social life remains unknown. Many brain areas are homologous and show similar patterns of activity in human and non-human primates. In both groups, cortical activity is modulated by hormones like oxytocin and by the action of certain genes that may affect individual differences in behaviour. Taken together, results suggest that differences in cooperation between the two groups are a matter of degree rather than constituting a fundamental, qualitative distinction.     

Self-Improvement for Team-Players: The Effects of Individual Effort on Aggregated Group Information

By putting effort into behaviours like foraging or scanning for predators, an animal can improve the correctness of its personal information about the environment. For animals living in groups, the individual can gain further information if it is able to assess public information about the environment from other group members. Earlier work has shown that consensus group decisions based upon the public information available within the group are more likely to be correct than decisions based upon personal information alone, given that each individual in a group has a fixed probability of being correct. This study develops a model where group members are able to improve their personal likelihood of making a correct decision by conducting some level of (costly) effort. I demonstrate that there is an evolutionarily stable level of effort for all the individuals within the group, and the effort made by an individual should decrease with increasing group size. The relevance of these results to social decision making is discussed: in particular, these results are similar to standard theoretical predictions about the amount of vigilance shown by individuals decreasing with increasing group size. However, this model suggests that these results could come about where individuals are coordinating their effort within the group (unlike standard models, which assume that all individual effort is independent of the actions of others). This ties in with experimental findings where individuals have been shown to monitor the efforts of others.     

Decision-making in a social world: Integrating cognitive ecology and social neuroscience

Understanding animal decision-making involves simultaneously dissecting and reconstructing processes across levels of biological organization, such as behavior, physiology, and brain function, as well as considering the environment in which decisions are made. Over the past few decades, foundational breakthroughs originating from a variety of model systems and disciplines have painted an increasingly comprehensive picture of how individuals sense information, process it, and subsequently modify behavior or states. Still, our understanding of decision-making in social contexts is far from complete and requires integrating novel approaches and perspectives. The fields of social neuroscience and cognitive ecology have approached social decision-making from orthogonal perspectives. The integration of these perspectives (and fields) is critical in developing comprehensive and testable theories of the brain.     

Community structure in social networks: applications for epidemiological modelling

During an infectious disease outbreak people will often change their behaviour to reduce their risk of infection. Furthermore, in a given population, the level of perceived risk of infection will vary greatly amongst individuals. The difference in perception could be due to a variety of factors including varying levels of information regarding the pathogen, quality of local healthcare, availability of preventative measures, etc. In this work we argue that we can split a social network, representing a population, into interacting communities with varying levels of awareness of the disease. We construct a theoretical population and study which such communities suffer most of the burden of the disease and how their awareness affects the spread of infection. We aim to gain a better understanding of the effects that community-structured networks and variations in awareness, or risk perception, have on the disease dynamics and to promote more community-resolved modelling in epidemiology.