Collective Adaptation in Multi-Agent Systems: How Predator Confusion Shapes Swarm-Like Behaviors

Abstract: Popular hypotheses about the origins of collective adaptation are related to two basic behaviours: protection from predators and a combined search for food resources. Among the anti-predator explanations, the predator confusion hypothesis suggests that groups of individuals moving in a swarm aim to overwhelm the predator while the dilution of risk hypothesis suggests that the probability of a single prey being targeted by a predator is lower in larger groups. In this paper, we explore how emergent behaviors arise from a predator-driven process as an adaptive response to external stimuli perceived as threatening. Moreover, we suggest a predator confusion process to provide a selective pressure for the prey to evolve group formations. We analyze the foraging and prey-predator dynamics evolved in terms of group density and formation, behavior consistency, predator evasion and success rate, and foraging rate. Two agents' perceptual models are compared. A local observation model, where agents can only see what's in their immediate vicinity, and a global observation model, where agents are able to see the predator at all times. Both models were evolved for predator avoidance, foraging and collision avoidance, using reinforcement learning in a simulated game environment. Our results suggest that the dilution of risk factor is sufficient to evolve group formations, and the predator confusion effect could play an important role in the evolution of collaborative behaviors. Finally, we show how variations in the information exchange of this social order can impact the global collective behaviors.