Understanding the dynamics of crowd behaviour

Crowds of tiny particles disperse as their environment becomes more disordered, according to scientists from UCL, Bilkent University and Université Pierre et Marie Curie. The new mechanism is counterintuitive and might help describe crowd behaviour in natural, real-world systems where many factors impact on individuals' responses to either gather or disperse. "Bacterial colonies, schools of fish, flocking birds, swarming insects and pedestrian flow all show collective and dynamic behaviours which are sensitive to changes in the surrounding environment and their dispersal or gathering can be sometimes the difference between life and death," said lead researcher, Dr Giorgio Volpe, UCL Chemistry. "The crowd often has different behaviours to the individuals within it and we don't know what the simple rules of motion are for this. If we understood these and how they are adapted in complex environments, we could externally regulate active systems. Examples include controlling the delivery of biotherapeutics in nanoparticle carriers to the target in the body, or improving crowd security in a panic situation." The study investigated the behaviour of active colloidal particles in a controllable system to find out the rules of motion for individuals gathering or dispersing in response to external factors. Colloidal particles are free to diffuse through a solution and for this study suspended silica microspheres were used.