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.     

Oxytocin and estrogen receptor alpha and beta knockout mice provide discriminably different odor cues in behavioral assays

Social behavior involves both the recognition and production of social cues. Mice with selective deletion (knockout) of either the gene for oxytocin (OT) or genes for the estrogen receptor (ER) -α or -β display impaired social recognition. In this study we demonstrate that these gene knockout mice also provide discriminably different social stimuli in behavioral assays. In an odor choice test, which is a measure of social interest and discrimination, outbred female Swiss-Webster mice discriminated the urine odors of male knockouts (KO: OTKO, αERKO, βERKO) from the odors of their wildtype littermates (WT: OTWT, αERWT, βERWT). Females showed marked initial choices of the urine odors of OTWT and βERWT males over those of OTKO and βERKO males, and αERKO males over αERWT males. The odors of OTKO and βERKO males also induced aversive, analgesic responses, with the odors of WTs having no significant effects. Odors of both the αERWT and αERKO males induced aversive, analgesic responses, with the odors of the WT inducing significantly greater analgesia. The odors of restraint stressed WT and KO males also elicited analgesia with, again, females displaying significantly greater responses to the odors of stressed OTKO and βERKO males than their WTs, and significantly lower analgesia to the odors of stressed αERKO than αERWT males. These findings show that the KO mice are discriminated from their WTs on the basis of odor and that the various KOs differ in the relative attractiveness/aversiveness of their odors. Therefore, in behavioral assays one causal route by which gene inactivation alters the social behavior of knockout mice may be mediated through the partners' modified responses to their odors.     

Field crickets change mating preferences using remembered social information

Plasticity in female mate choice can fundamentally alter selection on male ornaments, but surprisingly few studies have examined the role of social learning in shaping female mating decisions in invertebrates. We used the field cricket Teleogryllus oceanicus to show that females retain information about the attractiveness of available males based on previous social experience, compare that information with incoming signals and then dramatically reverse their preferences to produce final, predictable, mating decisions. Male ornament evolution in the wild may depend much more on the social environment and behavioural flexibility through learning than was previously thought for non-social invertebrates. The predictive power of these results points to a pressing need for theoretical models of sexual selection that incorporate effects of social experience.     

Drosophila melanogaster females change mating behaviour and offspring production based on social context

In Drosophila melanogaster, biological rhythms, aggression and mating are modulated by group size and composition. However, the fitness significance of this group effect is unknown. By varying the composition of groups of males and females, we show that social context affects reproductive behaviour and offspring genetic diversity. Firstly, females mating with males from the same strain in the presence of males from a different strain are infecund, analogous to the Bruce effect in rodents, suggesting a social context-dependent inbreeding avoidance mechanism. Secondly, females mate more frequently in groups composed of males from more than one strain; this mitigates last male sperm precedence and increases offspring genetic diversity. However, smell-impaired Orco mutant females do not increase mating frequency according to group composition; this indicates that social context-dependent changes in reproductive behaviour depend on female olfaction, rather than direct male-male interactions. Further, variation in mating frequency in wild-type strains depends on females and not males. The data show that group composition can affect variance in the reproductive success of its members, and that females play a central role in this process. Social environment can thus influence the evolutionary process.     

Male and female preference for conspecifics in a fish with male parental care (Percidae: Catonotus)

Speciation by sexual selection is commonly modeled as the divergent co-evolution of male signals and female preferences in geographically isolated populations. Upon secondary contact, females fail to recognize divergent males as suitable mates and exhibit a strong preference for their own type. The result is behavioral isolation and, if behavioral isolation is strong enough, there is an absence of gene flow between two species. Growing evidence of both mutual and male choice challenges the conventional role of females as primary regulators of species boundaries; however, to date, few studies have explicitly compared males and females for conspecific preference. The relative contribution of the two sexes to species boundaries therefore remains poorly understood. We examined the strength of preference for conspecifics in both males and females using two closely related species of darters. Males in these species exhibit substantial parental investment; therefore, we hypothesized that selection for male choosiness would result in male preference for conspecifics comparable to females’. Results show that females exhibited strong and significant preference for conspecific males; whereas, male preference for conspecific females was highly variable. Some males showed a strong preference for conspecifics while others preferred heterospecifics or showed no preference, resulting in a non-significant mean preference for conspecifics. Therefore, despite considerable parental investment by males in this system, our results suggest females play a larger role in regulating species boundaries.     

Behavioural social choice: a status report

Behavioural social choice has been proposed as a social choice parallel to seminal developments in other decision sciences, such as behavioural decision theory, behavioural economics, behavioural finance and behavioural game theory. Behavioural paradigms compare how rational actors should make certain types of decisions with how real decision makers behave empirically. We highlight that important theoretical predictions in social choice theory change dramatically under even minute violations of standard assumptions. Empirical data violate those critical assumptions. We argue that the nature of preference distributions in electorates is ultimately an empirical question, which social choice theory has often neglected. We also emphasize important insights for research on decision making by individuals. When researchers aggregate individual choice behaviour in laboratory experiments to report summary statistics, they are implicitly applying social choice rules. Thus, they should be aware of the potential for aggregation paradoxes. We hypothesize that such problems may substantially mar the conclusions of a number of (sometimes seminal) papers in behavioural decision research.     

Social traditions and social learning in capuchin monkeys (Cebus)

Capuchin monkeys (genus Cebus) have evolutionarily converged with humans and chimpanzees in a number of ways, including large brain size, omnivory and extractive foraging, extensive cooperation and coalitionary behaviour and a reliance on social learning. Recent research has documented a richer repertoire of group-specific social conventions in the coalition-prone Cebus capucinus than in any other non-human primate species; these social rituals appear designed to test the strength of social bonds. Such diverse social conventions have not yet been noted in Cebus apella, despite extensive observation at multiple sites. The more robust and widely distributed C. apella is notable for the diversity of its tool-use repertoire, particularly in marginal habitats. Although C. capucinus does not often use tools, white-faced capuchins do specialize in foods requiring multi-step processing, and there are often multiple techniques used by different individuals within the same social group. Immatures preferentially observe foragers who are eating rare foods and hard-to-process foods. Young foragers, especially females, tend to adopt the same foraging techniques as their close associates.