title: On the duality between interaction responses and mutual positions in flocking and schooling.
abstract: Recent research in animal behaviour has contributed to determine how alignment, turning responses, and changes of speed mediate flocking and schooling interactions in different animal species. Here, we propose a complementary approach to the analysis of flocking phenomena, based on the idea that animals occupy preferential, anysotropic positions with respect to their neighbours, and devote a large amount of their interaction responses to maintaining their mutual positions. We test our approach by deriving the apparent alignment and attraction responses from simulated trajectories of animals moving side by side, or one in front of the other. We show that the anisotropic positioning of individuals, in combination with noise, is sufficient to reproduce several aspects of the movement responses observed in real animal groups. This anisotropy at the level of interactions should be considered explicitly in future models of flocking and schooling. By making a distinction between interaction responses involved in maintaining a preferred flock configuration, and interaction responses directed at changing it, our work provides a frame to discriminate movement interactions that signal directional conflict from interactions underlying consensual group motion.
authors.affiliation: Paris Interdisciplinary Energy Research Institute, Paris Diderot University, 10 rue Alice Domon et Léonie Duquet, Paris, 75013 France.
authors.forename: Andrea
authors.initials: A
authors.lastname: Perna
authors.affiliation: Laboratoire Matiere Systemes Complexes, Paris Diderot University, 10 rue Alice Domon et Léonie Duquet, Paris, 75013 France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Grégoire
authors.affiliation: Mathematics Department, Uppsala University, Lägerhyddsvägen 1, Uppsala, 75754 Sweden ; Chair of Sociology, in particular of Modeling and Simulations, ETH Zürich, Clausiusstrasse 50, Zürich, 8092 Switzerland.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Mann
keywords: Collective motion; Flocking; Movement analysis; Schooling