Abstract: Social behaviour was observed in individually marked goats in two herds. The goats from one herd (n = 98) were horned, those of the other herd (n = 83) were polled. By recording agonistic interactions within the herds, a dominance index was determined for each animal. In both herds, intervention took place. Intervention is defined as one animal pushing in between two fighters, and thus ending the fight. More cases of intervention took place per individual animal amongst the horned goats than amongst the polled ones. Goats which intervened in fights on several occasions usually had a high dominance index. Members of the herd which were observed intervening only once had an average dominance index in both herds of almost 0.5. In some cases, goats very low in the rank order intervened a fight. Only rarely did the intervenors have a lower dominance index than the two fighters. In 103 cases, the direct dominance relationship between a fighting animal and the intervenor was known. In 95 cases (92.2%), the intervenor was dominant to the herd member in this fight and in just eight cases (7.8%), it was subordinate. It could not be determined what advantage the intervenor gained from its activity. It is possible that, at least in certain cases, a particularly relationship existed between the intervenor and one of the fighters.

Abstract: Networks of coupled dynamical systems have been used to model biological oscillators Josephson junction arrays excitable media, neural networks spatial games11, genetic control networks12 and many other self-organizing systems. Ordinarily, the connection topology is assumed to be either completely regular or completely random. But many biological, technological and social networks lie somewhere between these two extremes. Here we explore simple models of networks that can be tuned through this middle ground: regular networks 'rewired' to introduce increasing amounts of disorder. We find that these systems can be highly clustered, like regular lattices, yet have small characteristic path lengths, like random graphs. We call them 'small-world' networks, by analogy with the small-world phenomenon (popularly known as six degrees of separation). The neural network of the worm Caenorhabditis elegans, the power grid of the western United States, and the collaboration graph of film actors are shown to be small-world networks. Models of dynamical systems with small-world coupling display enhanced signal-propagation speed, computational power, and synchronizability. In particular, infectious diseases spread more easily in small-world networks than in regular lattices.

Abstract: In a series of studies, we evaluated the susceptibility of radioimmunoassays (RIA) for saliva cortisol to interference effects caused by oral stimulants used to facilitate saliva collection in studies with children. When added directly to saliva samples, oral stimulants (drink mix crystals) artificially inflated estimated cortisol concentrations. The magnitude of the interference effect was concentration-dependent and more pronounced for some stimulants and RIA procedures than for others. Analysis of samples collected using oral stimulants from child and adult participants confirmed stimulant interference as an extraneous source of variability in measured saliva cortisol. Associations between serum and saliva cortisol and between saliva cortisol and “behavioral” variables were attenuated by stimulant interference. A survey of six large child studies estimated interference effects, indexed by low sample pH, to be present in 14.7% of the 1,148 total saliva samples, or 2%-54% (M= 22%) of samples within each study. Recommendations to minimize the impact of stimluant interference in studies involving salivary cortisol in the context of child health and development are outlined.