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1.  Beneficial laggards: multilevel selection, cooperative polymorphism and division of labour in threshold public good games 
The origin and stability of cooperation is a hot topic in social and behavioural sciences. A complicated conundrum exists as defectors have an advantage over cooperators, whenever cooperation is costly so consequently, not cooperating pays off. In addition, the discovery that humans and some animal populations, such as lions, are polymorphic, where cooperators and defectors stably live together -- while defectors are not being punished--, is even more puzzling. Here we offer a novel explanation based on a Threshold Public Good Game (PGG) that includes the interaction of individual and group level selection, where individuals can contribute to multiple collective actions, in our model group hunting and group defense.
Our results show that there are polymorphic equilibria in Threshold PGGs; that multi-level selection does not select for the most cooperators per group but selects those close to the optimum number of cooperators (in terms of the Threshold PGG). In particular for medium cost values division of labour evolves within the group with regard to the two types of cooperative actions (hunting vs. defense). Moreover we show evidence that spatial population structure promotes cooperation in multiple PGGs. We also demonstrate that these results apply for a wide range of non-linear benefit function types.
We demonstrate that cooperation can be stable in Threshold PGG, even when the proportion of so called free riders is high in the population. A fundamentally new mechanism is proposed how laggards, individuals that have a high tendency to defect during one specific group action can actually contribute to the fitness of the group, by playing part in an optimal resource allocation in Threshold Public Good Games. In general, our results show that acknowledging a multilevel selection process will open up novel explanations for collective actions.
PMCID: PMC2989973  PMID: 21044340
2.  Evaluation of a comprehensive AIDS education curriculum in Hungary – the role of good educators1 
Journal of adolescence  2002;25(5):495-508.
The aim of this research was to evaluate a school-based AIDS education programme in Eastern Europe. Four evaluation segments were undertaken: process and outcome evaluations of the training of AIDS educators and of the educational activities for students. While most AIDS education curricula focus on the content of the education, our findings demonstrate that other aspects — including the characteristics of those educators who appear to be most effective, the way in which education is affected by teachers’ attitudes, and the cultural implications of transferring programmes from one country to another – also need to be considered, especially in international environments.
PMCID: PMC2925669  PMID: 12234556
3.  Separating equilibria in continuous signalling games. 
Much of the literature on costly signalling theory concentrates on separating equilibria of continuous signalling games. At such equilibria, every signaller sends a distinct signal, and signal receivers are able to exactly infer the signaller's condition from the signal sent. In this paper, we introduce a vector-field solution method that simplifies the process of solving for separating equilibria. Using this approach, we show that continuous signalling games can have low-cost separating equilibria despite conflicting interests between signaller and receiver. We find that contrary to prior arguments, honesty does not require wasteful signals. Finally, we examine signalling games in which different signallers have different minimal-cost signals, and provide a mathematical justification for the argument that even non-signalling traits will be exaggerated beyond their phenotypic optimum when they are used by other individuals to judge condition or quality.
PMCID: PMC1693066  PMID: 12495516
4.  Language Evolution 
PLoS Biology  2004;2(10):416.
How did language develop and evolve? Here, linguists, cognitive scientists, behavioural ecologists, and theoretical biologists all offer their disparate views on this emerging field
PMCID: PMC521730

Results 1-4 (4)