biostudies-literatureUnknown16(154)Perna AGroup living animals form aggregations and flocks that remain cohesive in spite of internal movements of individuals. This is possible because individual group members repeatedly adjust their position and motion in response to the position and motion of other group members. Here, we develop a theoretical approach to address the question, what general features-if any-underlie the interaction rules that mediate group stability in animals of all species? We do so by considering how the spatial organization of a group would change in the complete absence of interactions. Without interactions, a group would disperse in a way that can be easily characterized in terms of Fick's diffusion equations. We can hence address the inverse theoretical problem of finding the individual-level interaction reJournal of the Royal Society, Interface20190212https://www.ebi.ac.uk/biostudies/studies/S-EPMC6544880biostudies-literatureWeber's Law-based perception and the stability of animal groups.PMC6544880Perna AFacchini GDeneubourg JLfalseWeber's Law-based perception and the stability of animal groups.Group living animals form aggregations and flocks that remain cohesive in spite of internal movements of individuals. This is possible because individual group members repeatedly adjust their position and motion in response to the position and motion of other group members. Here, we develop a theoretical approach to address the question, what general features-if any-underlie the interaction rules that mediate group stability in animals of all species? We do so by considering how the spatial organization of a group would change in the complete absence of interactions. Without interactions, a group would disperse in a way that can be easily characterized in terms of Fick's diffusion equations. We can hence address the inverse theoretical problem of finding the individual-level interaction re2019-01-01T00:00:00Z2019 May2025-04-04T10:29:53.547Z2020-11-22T08:28:54ZS-EPMC65448803108826010.1098/rsif.2019.0212