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1.  Why does costly signalling evolve? Challenges with testing the handicap hypothesis 
Animal behaviour  2015;110:e9-e12.
PMCID: PMC4783833  PMID: 26973349
action-response games; animal communication; handicap principle; receiver psychology; strategic costs
2.  Deception Undermines the Stability of Cooperation in Games of Indirect Reciprocity 
PLoS ONE  2016;11(1):e0147623.
Indirect reciprocity is often claimed as one of the key mechanisms of human cooperation. It works only if there is a reputational score keeping and each individual can inform with high probability which other individuals were good or bad in the previous round. Gossip is often proposed as a mechanism that can maintain such coherence of reputations in the face of errors of transmission. Random errors, however, are not the only source of uncertainty in such situations. The possibility of deceptive communication, where the signallers aim to misinform the receiver cannot be excluded. While there is plenty of evidence for deceptive communication in humans the possibility of deception is not yet incorporated into models of indirect reciprocity. Here we show that when deceptive strategies are allowed in the population it will cause the collapse of the coherence of reputations and thus in turn it results the collapse of cooperation. This collapse is independent of the norms and the cost and benefit values. It is due to the fact that there is no selection for honest communication in the framework of indirect reciprocity. It follows that indirect reciprocity can be only proposed plausibly as a mechanism of human cooperation if additional mechanisms are specified in the model that maintains honesty.
PMCID: PMC4732813  PMID: 26824895
3.  Attention-Seeking Displays 
PLoS ONE  2015;10(8):e0135379.
Animal communication abounds with extravagant displays. These signals are usually interpreted as costly signals of quality. However, there is another important function for these signals: to call the attention of the receiver to the signaller. While there is abundant empirical evidence to show the importance of this stage, it is not yet incorporated into standard signalling theory. Here I investigate a general model of signalling - based on a basic action-response game - that incorporates this searching stage. I show that giving attention-seeking displays and searching for them can be an ESS. This is a very general result and holds regardless whether only the high quality signallers or both high and low types give them. These signals need not be costly at the equilibrium and they need not be honest signals of any quality, as their function is not to signal quality but simply to call the attention of the potential receivers. These kind of displays are probably more common than their current weight in the literature would suggest.
PMCID: PMC4545794  PMID: 26287489
4.  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
5.  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
6.  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
7.  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 1-7 (7)