Are the Flocks Critical Phenomena?

Almost all flock models are constructed using a self-propelled particle system (SPPs). In an SPP method, each individual will interact with neighbors found within a certain radius. Recent investigations are forcing us to reconsider the notion of the neighborhood in flocks. Cavagna et al. found a scale-free correlation in which the sub-flocks use the same information and where their size is proportional to the flock size. This finding indicates that the flock neighborhood dynamically changes the shape and formation of the flock. They defined this state of the flock as the "noise critical phenomenon". However, is it a sufficient interpretation of the scale-free correlation? The agent of the type-token model, which we proposed, changes its neighborhood by adjusting between the type and token cognitions. These differences in the neighborhood of each agent enables their flock to rapidly change direction without external noise and shows a scale-free correlation that is supported with empirical research. The typetoken model suggests that the flock emerges as a scale-free correlation without considering noise critical phenomena.