My research involves the use of mathematical models and computer simulations to study various ecological questions. The general themes of my research can be categorized into the following areas (for a complete list of my publications please see my Google scholar profile).
Social information use and collective decision-making
Many social animals (including humans) make use of the actions or opinions of others when making a decision or forming an opinion. There are several benefits to this. Often it is useful to follow others simply to avoid being in a minority, while in other scenarios the information gained from others can be valuable, since it provides another viewpoint of the environment.
However using social information can also have negative consequences. Groups may become less accurate when situations change, and unable to escape locked in beliefs or opinions once they have taken hold. Understanding the trade-offs and potential pitfalls of using social information is an important challenge. In my research I use mathematical models to explore the role of group structure on collective decision-making, how accuracy scales with group size and how individual strategies of influence can alter the dynamics of opinion formation.
Relevant publications
Social information use and the evolution of unresponsiveness in collective systems
CJ Torney, T Lorenzi, ID Couzin, SA Levin, Journal of the Royal Society Interface (in press)Collective learning and optimal consensus decision-making
A Kao, N Miller, CJ Torney, A Hartnett, ID Couzin, PLoS Computational Biology 10 (8), e1003762 (2014)Decision accuracy and the role of spatial interaction in opinion dynamics
Torney, C.J., Levin, S.A., Couzin, I.D., Journal of Statistical Physics, (2013) 10.1007/s10955-013-0700-5
Uninformed individuals promote democratic consensus in animal groups
Couzin, I.D., Ioannou, C.C., Demirel, G., Gross, T., Torney, C.J., Hartnett, A., Conradt, L., Levin, S.A. & Leonard, N.E., Science, 334 (6062), 1578-1580 (2011) (free reprint available here)
Animal movement, search and navigation
Collective movement is perhaps the most obvious example of socially influenced decisions in nature. Animal groups such as fish schools, or bird flocks, frequently remain cohesive while they move in a common direction. Many species that migrate long distances tend to do so in large groups. This can increase survival probability in different ways, including increasing the capacity of the group to respond to vital directional cues in the environment.
In both a theoretical and experimental setting I have investigated this issue and demonstrated that groups are often more intelligent than individuals in isolation.
On the left is an animation showing how simulated individuals are able to track an advected odour plume in a turbulent environment by modulating the strength of their social response. On the right is an experimental movie which outlines the process involved in investigating this question in schooling fish.
To address these questions in a natural setting, I have also begun to use UAVs (Unmanned Aerial Vehicles) for data collection. A short movie about our work in the Serengeti is shown below.
Relevant publications
On the evolutionary interplay between dispersal and local adaptation in heterogeneous environments
A Berdahl, CJ Torney, E Schertzer, SA Levin, Evolution (2015)Emergent sensing of complex environments by mobile animal groups
A Berdahl, CJ Torney, CC Ioannou, JJ Faria, ID Couzin, Science, 339 (6119), 576-576 (2013) (free reprint available here)Tactile interaction leads to coherent motion and enhanced chemotaxis of migrating cells
L Coburn, L Cerone, CJ Torney, ID Couzin, Z Neufeld, Physical Biology, 10 (046002), (2013) 
Context-dependent interaction leads to emergent search behaviour in social aggregates
CJ Torney, Z Neufeld and ID Couzin, Proceedings of the National Academy of Sciences, 106-52 (2009)
Phototactic clustering of swimming micro-organisms in a turbulent velocity field
CJ Torney and Z Neufeld, Phys Rev Let, 101-7 (2008)
Transport and aggregation of self-propelled particles in fluid flows
CJ Torney and Z Neufeld, Phys Rev Let, 99-7 (2007)
Multilevel selection and the conflict between individual and group interest
While groups have the potential to outperform individuals, conflicts of interest between the group and its constituents often lead to sub-optimal collective systems. Understanding the evolution of group function is a key focus of my research program, with the aim of increasing our knowledge of how natural populations function, as well as informing strategies for engineering artificial decentralized systems.
Relevant publications
Social information use and the evolution of unresponsiveness in collective systems
CJ Torney, T Lorenzi, ID Couzin, SA Levin, Journal of the Royal Society Interface (in press)Signalling and the evolution of cooperative foraging in dynamic environments
CJ Torney, A Berdahl and ID Couzin, PLoS Computational Biology 7(9), e1002194 (2011)Specialization and evolutionary branching within migratory populations
CJ Torney, SA Levin, and ID Couzin, Proceedings of the National Academy of Sciences, 107-47 (2010)