Conformist learning in nine-spined sticklebacks' foraging decisions

Theoretical analyses have reported that in most circumstances where natural selection favours reliance on social learning, conformity (positive frequency-dependent social learning) is also favoured. These findings suggest that much animal social learning should involve a copy-the-majority strategy, yet there is currently surprisingly little evidence for conformist learning among animals. Here, we investigate this possibility in the nine-spined stickleback (Pungitius pungitius) by manipulating the number of demonstrator fish at two feeders, one rich and one poor, during a demonstration phase and evaluating how this affects the likelihood that the focal fish copy the demonstrators'' apparent choices. As predicted, we observed a significantly increased level of copying with increasing numbers of demonstrators at the richer of the two feeders, with copying increasing disproportionately, rather than linearly, with the proportion of demonstrators at the rich foraging patch. Control conditions with non-feeding demonstrators showed that this was not simply the result of a preference for shoaling with larger groups, implying that nine-spined sticklebacks copy in a conformist manner.     

The role of conformity in foraging when personal and social information conflict

There is currently considerable interest in the interplay betweenpersonal and social information in decision-making processes.Two experiments are presented exploring the relative use ofprior personal information and subsequent social informationin foraging decisions of guppies. Experiment 1 tested the assumptionthat when the use of information acquired through personal experienceis not costly, conflicting social information will be ignored.The assumption was confirmed because, when given a choice betweenfeeding at two food patches, at one of which they had previouslyseen conspecifics feed, individual fish with prior experienceof feeding at the alternative site chose the alternative, whereasfish with no prior experience chose the site at which theirconspecifics had fed. Experiment 2 tested theoretical predictionsthat when the use of information acquired through personal experienceis potentially costly, conflicting social information will beweighed more heavily than will personal information. The predictionwas confirmed because, when given a choice between feeding attwo food patches, one at which they had previously seen conspecificsfeed and one behind a visual barrier, individual fish with priorexperience of feeding behind the barrier chose the site at whichtheir conspecifics had fed. These findings suggest that conformitycan promote social learning in naïve individuals, but priorexperience can insulate individuals from conformity providedthe costs of relying on that experience are small. In addition,the experiments highlight the fact that personal and socialinformation are not always weighed equally.     

Ground squirrel sociality and the quest for the 'holy grail': does kinship influence behavioral discrimination by juvenile Columbian ground squirrels?

Research on social discrimination by ground-dwelling squirrelshas focused on die ability of squirrels to discriminate kinfrom nonkin. The predominant mechanism underlying that abilityis social familiarization. Although familiarity-based mechanismsmay result in kin discrimination where kin are associated reliablyin space and time, past investigations have largely ignoredadditional levels of social discrimination that may result fromongoing familiarization in the natural context Here we presentdata from a cross-fostering experiment that examines the relativecontributions of rearing association and relatedness to subsequentbehavioral discrimination among juvenile Columbian ground squirrels(Spermophilus columbianus). Rearing association significantlyinfluenced recognitive and agonistic behavior among juvenileswhile relatedness proved insignificant in affecting behavioralinteractions. Thus, direct familiarization in the natal burrowis both sufficient and necessary to account for the transitiveappearance of kin-differential behavior among newly emergedjuveniles documented in previous studies. Reanalyses of datafrom field experiments on S. columbianus social discriminationfail to detect any evidence of kin-biased behavior, and evidencefrom studies purporting to document kinship effects is equivocalat best Taken together with more recent findings, the scantdata suggestive of kin discrimination by Columbian ground squirrelsare best viewed as an artifact of selection promoting the discriminationof familiar from unfamiliar individuals at the level of localizedgroups. Fitness payoffs of such discrimination may accrue viareciprocal altruism, or ‘dear-enemy’ recognition,and would promote the evolution and maintenance of socialitywithout recourse to indirect components of inclusive fitnesscommonly invoked to explain ground squirrel sociality. Finally,our data call into doubt the notion that mechanisms allowingthe direct assessment of kinship should be common among themore social sciurids.     

The evolutionary basis of human social learning

Humans are characterized by an extreme dependence on culturally transmitted information. Such dependence requires the complex integration of social and asocial information to generate effective learning and decision making. Recent formal theory predicts that natural selection should favour adaptive learning strategies, but relevant empirical work is scarce and rarely examines multiple strategies or tasks. We tested nine hypotheses derived from theoretical models, running a series of experiments investigating factors affecting when and how humans use social information, and whether such behaviour is adaptive, across several computer-based tasks. The number of demonstrators, consensus among demonstrators, confidence of subjects, task difficulty, number of sessions, cost of asocial learning, subject performance and demonstrator performance all influenced subjects' use of social information, and did so adaptively. Our analysis provides strong support for the hypothesis that human social learning is regulated by adaptive learning rules.     

Better stay together: pair bond duration increases individual fitness independent of age-related variation

Prolonged pair bonds have the potential to improve reproductive performance of socially monogamous animals by increasing pair familiarity and enhancing coordination and cooperation between pair members. However, this has proved very difficult to test robustly because of important confounds such as age and reproductive experience. Here, we address limitations of previous studies and provide a rigorous test of the mate familiarity effect in the socially monogamous blue-footed booby, Sula nebouxii, a long-lived marine bird with a high divorce rate. Taking advantage of a natural disassociation between age and pair bond duration in this species, and applying a novel analytical approach to a 24 year database, we found that those pairs which have been together for longer establish their clutches five weeks earlier in the season, hatch more of their eggs and produce 35% more fledglings, regardless of age and reproductive experience. Our results demonstrate that pair bond duration increases individual fitness and further suggest that synergistic effects between a male and female''s behaviour are likely to be involved in generating a mate familiarity effect. These findings help to explain the age- and experience-independent benefits of remating and their role in life-history evolution.     

Social development in nursery-reared pigtailed macaques (Macaca nemestrina)

The social development of 240 nursery-reared pigtailed macaques (Macaca nemestrina) was studied from postnatal weeks 4 to 32. The objectives of the study were to document developmental trends and evaluate social behavior in laboratory-reared M. nemestrina raised at the University of Washington Infant Primate Laboratory, and to identify husbandry factors that might affect early social development. Only infants who had not undergone invasive postnatal experimental manipulation and had no chronic illness or injuries were included in the study. Infants were separated from their mothers and housed singly, but had access to peers for 30 min a day, 5 days a week, in a large playroom. Play and social behaviors emerged early in development, increased during the developmental period studied and occupied a large portion of the infants' time budgets. Although disturbance behaviors occurred with some frequency and duration early in development, they occupied a very small portion of the infants' time budget at 8 months of age. Weaning from infant formula at 16–19 weeks retarded development of play behavior. Permanent removal of a cloth comforter (diaper) during weeks 20–24 had no long-term behavioral effects. It was concluded that at 8 months of age these infants showed relatively normal species-typical behavioral repertoires. Am J Primatol 41:23–35, 1997. © 1997 Wiley-Liss, Inc.     

The effects of familiarity and social hierarchy on group membership decisions in a social fish

Members of animal groups face a trade-off between the benefits of remaining with a familiar group and the potential benefits of dispersing into a new group. Here, we examined the group membership decisions of Neolamprologus pulcher, a group-living cichlid. We found that subordinate helpers showed a preference for joining familiar groups, but when choosing between two unfamiliar groups, helpers did not preferentially join groups that maximized their social rank. Rather, helpers preferred groups containing larger, more dominant individuals, despite receiving significantly more aggression within these groups, possibly owing to increased protection from predation in such groups. These results suggest a complex decision process in N. pulcher when choosing among groups, dependent not only on familiarity but also on the social and life-history consequences of joining new groups.     

Social implications of the battle of the sexes: sexual harassment disrupts female sociality and social recognition

Across sexually reproducing species, males and females are in conflict over the control of reproduction. At the heart of this conflict in a number of taxa is male harassment of females for mating opportunities and female strategies to avoid this harassment. One neglected consequence that may result from sexual harassment is the disruption of important social associations. Here, we experimentally manipulate the degree of sexual harassment that wild female guppies (Poecilia reticulata) experience by establishing replicated, semi-natural pools with different population sex ratios. We quantify the effects of sexual harassment on female social structure and the development of social recognition among females. When exposed to sexual harassment, we found that females had more disparate social networks with limited repeated interactions when compared to females that did not experience male harassment. Furthermore, females that did not experience harassment developed social recognition with familiar individuals over an 8-day period, whereas females that experienced harassment did not, an effect we suggest is due to disruption of association patterns. These results show that social network structure and social recognition can be affected by sexual harassment, an effect that will be relevant across taxonomic groups and that we predict will have fitness consequences for females.