289 research outputs found
Formalising the multidimensional nature of social networks
Individuals interact with conspecifics in a number of behavioural contexts or
dimensions. Here, we formalise this by considering a social network between n
individuals interacting in b behavioural dimensions as a nxnxb multidimensional
object. In addition, we propose that the topology of this object is driven by
individual needs to reduce uncertainty about the outcomes of interactions in
one or more dimension. The proposal grounds social network dynamics and
evolution in individual selection processes and allows us to define the
uncertainty of the social network as the joint entropy of its constituent
interaction networks. In support of these propositions we use simulations and
natural 'knock-outs' in a free-ranging baboon troop to show (i) that such an
object can display a small-world state and (ii) that, as predicted, changes in
interactions after social perturbations lead to a more certain social network,
in which the outcomes of interactions are easier for members to predict. This
new formalisation of social networks provides a framework within which to
predict network dynamics and evolution under the assumption that it is driven
by individuals seeking to reduce the uncertainty of their social environment.Comment: 16 pages, 4 figure
The âstrength of weak tiesâ among female baboons : fitness-related benefits of social bonds
Thanks to Cape Nature Conservation for permission to work at De Hoop, and to all the graduate students and field assistants who contributed to our long-term data-base. LB was supported by NSERC Canada Research Chair and Discovery Programs; SPH was supported by the NRF (South Africa) and NSERC Discovery Grants during the writing of this manuscript. We are grateful to one anonymous reviewer and, in particular, Lauren Brent for invaluable feedback on earlier drafts of our manuscript.Peer reviewedPostprin
Experts in action: why we need an embodied social brain hypothesis
The anthropoid primates are known for their intense sociality and large brain size. The idea that these might be causally related has given rise to a large body of work testing the âsocial brain hypothesis'. Here, the emphasis has been placed on the political demands of social life, and the cognitive skills that would enable animals to track the machinations of other minds in metarepresentational ways. It seems to us that this position risks losing touch with the fact that brains primarily evolved to enable the control of action, which in turn leads us to downplay or neglect the importance of the physical body in a material world full of bodies and other objects. As an alternative, we offer a view of primate brain and social evolution that is grounded in the body and action, rather than minds and metarepresentation
Proof of principle : the adaptive geometry of social foragers
Acknowledgments We thank Cape Nature for permission to undertake the study. We thank Dr Matt Grove and two anonymous referees for comments and suggestions that improved the manuscript substantially. This research was funded by grants from the Leakey Foundation, National Science and Engineering Research Council, Canada to S.P.H. and L.B., and by the National Research Foundation, South Africa to S.P.H. His co-authors dedicate this paper to the memory of P.M.R.C. The authors declare no competing interests.Peer reviewedPostprin
Scaling violations: Connections between elastic and inelastic hadron scattering in a geometrical approach
Starting from a short range expansion of the inelastic overlap function,
capable of describing quite well the elastic pp and scattering data,
we obtain extensions to the inelastic channel, through unitarity and an impact
parameter approach. Based on geometrical arguments we infer some
characteristics of the elementary hadronic process and this allows an excellent
description of the inclusive multiplicity distributions in and
collisions. With this approach we quantitatively correlate the violations of
both geometrical and KNO scaling in an analytical way. The physical picture
from both channels is that the geometrical evolution of the hadronic
constituents is principally reponsible for the energy dependence of the
physical quantities rather than the dynamical (elementary) interaction itself.Comment: 16 pages, aps-revtex, 11 figure
Common HLA Alleles Associated with Health, but Not with Facial Attractiveness
Three adaptive hypotheses have been proposed to explain the link between the human leucocyte antigen (HLA) genes, health measures and facial attractiveness: inbreeding avoidance, heterozygote advantage and frequency-dependent selection. This paper reports findings that support a new hypothesis relating HLA to health. We suggest a new method to quantify the level of heterozygosity. HLA heterozygosity did not significantly predict health measures in women, but allele frequency did. Women with more common HLA alleles reported fewer cold and flu bouts per year, fewer illnesses in the previous year and rated themselves healthier than women with rare alleles. To our knowledge, this is the first study to show a positive correlation between HLA allele frequency and general health measures. We propose that certain common HLA alleles confer resistance to prevalent pathogens. Nevertheless, neither HLA heterozygosity nor allele frequency significantly predicted how healthy or attractive men rated the female volunteers. Three non-mutually exclusive explanations are put forward to explain this finding
Total Cross Section, Inelasticity and Multiplicity Distributions in Proton -- Proton Collisions
Multiparticle production in high energy proton -- proton collisions has been
analysed in the frame of Strongly Correlated Quark Model (SCQM) of the hadron
structure elaborated by the author. It is shown that inelasticity decreases at
high energies and this effect together with the total cross section growth and
the increasing with collision energy the masses of intermediate clusters result
in the violation of KNO -- scaling.Comment: 21 pages, 11 figures, submitted to Yad. Fisik
Eikonal representation in the momentum-transfer space
By means of empirical fits to the differential cross section data on pp and
p(bar)p elastic scattering, above 10 GeV (center-of-mass energy), we determine
the eikonal in the momentum - transfer space (q^2- space). We make use of a
numerical method and a novel semi-analytical method, through which the
uncertainties from the fit parameters can be propagated up to the eikonal in
the - space. A systematic study of the effect of the experimental
information at large values of the momentum transfer is developed and discussed
in detail. We present statistical evidence that the imaginary part of the
eikonal changes sign in the q^2- space and that the position of the zero
decreases as the energy increases; after the position of the zero, the eikonal
presents a minimum and then goes to zero through negative values. We discuss
the applicability of our results in the phenomenological context, outlining
some connections with nonperturbative QCD. A short review and a critical
discussion on the main results concerning "model-independent" analyses are also
presented.Comment: 18 pages, 17 figures, 4 tables, svjour.cls. Revised discussion on the
proton's electromagnetic form factor and references added. To appear in Eur.
Phys. J.
Sick and tired : sickness behaviour, polyparasitism and food stress in a gregarious mammal
Although sickness behaviour in response to non-lethal parasites has been documented in wild animals, it remains unclear how social and environmental stress might also shape an animalâs behavioural response to parasitism, nor do we know whether simultaneous infection with more than one parasite changes the way animals respond. Here, we combine physiological, environmental, behavioural and parasite measures to investigate behavioural responses to infection in wild vervet monkeys (Chlorocebus pygerythrus) living in a semi-arid region of South Africa. We quantified both activity budget and behavioural predictability to investigate the occurrence of sickness behaviour and infection with two non-lethal gastrointestinal parasite genera. Higher parasite load was linked to an increase in the time spent resting. However, the nature of the relationship with other behaviours was contingent on both the parasite genus in question and parasite species interacted, highlighting the importance of considering co-infection. Overall, food availability was the dominant predictor of behavioural change suggesting that, for monkeys living in a more extreme environment, coping with ecological stress may override the ability to modulate behaviour in response to other physiological stressors. Our findings provide insight into how animals living in harsh environments find ways to cope with parasite infection, avoidance and transmission.
SIGNIFICANCE STATEMENT : Sickness behaviour is a suite of behaviours that occur in response to infection that may serve as an adaptive response to cope with infection. For wild animals, the ability to express sickness behaviour will be modulated by the presence of other competing stressors. Hence, the patterns shown are likely to be more complex than under captive conditions, which is where most of our knowledge of sickness behaviour comes from. Using physiological, environmental, behavioural and parasite measures, we demonstrate that although vervet monkeys (Chlorocebus pygerythrus) living in a semi-arid region of South Africa do exhibit sickness behaviours, this is contingent on the parasite genus in question. Further, food availability was the dominant predictor of behavioural change suggesting that, for monkeys living in a more extreme environment, coping with severe ecological stress may override the ability to express sickness behaviour in an adaptive fashion.National Research Foundation (South Africa), Natural Science and Engineering Research Council of Canada (NSERC) Discovery Grants, the Canada Research Chairs Program, a Leakey Foundation Franklin Mosher Baldwin Memorial Fellowship and a Senior Post-doctoral Fellowship at the University of Pretoria.http://link.springer.com/journal/265hj2022Mammal Research Institut
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