Perception of Motion Salience Shapes the Emergence of Collective Motions

As one of the most common and spectacular manifestations of coordinated behavior, collective motion is the spontaneous emergence of the ordered movement in a system consisting of many self-propelled agents, e.g., flocks of birds, schools of fish, herds of animals, and human crowds. Despite extensive studies on collective motions, a systems-level understanding of different motion patterns of collective behaviors is still lacking. This further hinders the adoption of bio-inspired mechanisms for applications of swarm robotics. Here, by leveraging three large bird-flocking datasets, we systematically investigate the emergence of different patterns of collective motions: mobbing, circling , and transit . We find that flocks with higher maneuverable motions (i.e., mobbing and circling ) prefer to evolve a more nested structure of leader-follower (LF) relations and a clear hierarchy to mitigate the damage of individual freedom to group cohesion. In contrast, flocks with smooth motion (i.e., transit ) do not display this tactful strategy to organize the group. To explain this empirical finding, we propose a measure based on the perception of motion salience (MS) to quantify the trade-off between individual freedom and group cohesion. Moreover, we perform the correlation analysis between LF and MS, finding that individuals with higher MS tend to lead the group with higher maneuverable motions. Those findings prompt us to develop a swarm model with adaptive MS-based (AMS) interactions and confirm that AMS interactions are responsible for the emergence of nested and hierarchical LF relations in the flocks with highly maneuverable motions. Finally, we implement AMS interactions in swarm robotics that consists of ∼10[2][1] miniature mobile robots. The swarm experiments of collective following and collective evacuation demonstrate that AMS interactions not only empower the swarm to promptly respond to the transient perturbation but also strengthen the self-organization of collective motions in terms of temporal cognition. ### Competing Interest Statement The authors have declared no competing interest. [1]: #ref-2