"BACKGROUND In interactive contexts (e.g. mate choice, aggression), individuals face a great deal of uncertainty over the behaviour of others. This makes decision-making difficult, because the best thing to do depends critically on the make-up of the social environment and the strategies others adopt. Current theory is poorly equipped to deal with these decisions because it typically assumes that individuals have perfect knowledge of the situation in which they find themselves, including the states of others with whom they interact. OBJECTIVES My project will investigate the evolution of behavioural strategies for dealing with uncertainty, focusing on aggression and mate choice. This will require an interdisciplinary approach, integrating economic concepts traditionally used in behavioural ecology with a more psychological perspective. STRATEGY To achieve this goal I will combine theory with empirical work and collaborate with world-leading researchers with the relevant expertise. In the outgoing phase, I will study aggressive behaviour in real animals to test novel predictions of my earlier models on uncertainty, running tests on captive zebra finches and examining patterns of aggression in data from humans. In the return phase, I will develop new models of mating behaviour that explicitly consider the uncertainty inherent in systems of mutual choice, using a Bayesian approach. RELEVANCE The project will considerably enhance my international, interdisciplinary research experience and train me specifically in the use of longitudinal databases for understanding behavioural development. With expert mentoring and a Personal Career Development Plan, this new knowledge and training will boost my professional development as an independent research scientist. At the same time, by testing key predictions from recent theory and developing new models of behaviour under uncertainty, the project has the potential to make an important contribution to EU scientific excellence."