Controlling noisy herds.

The wisdom of the crowd breaks down in small groups. While large flocks exhibit swarm intelligence to evade predators, small groups display erratic behavior, oscillating between unity and discord. We investigate these dynamics using small groups of sheep controlled by shepherd dogs in century-old sheepdog trials, proposing a two-parameter stochastic dynamic framework. Our model employs pressure (stimulus intensity) and lightness (response isotropy) to simulate herding and shedding behaviors. Light sheep rapidly achieve a stable herding state, while heavy sheep exhibit intermittent herding and orthogonal alignment to the dog. High response isotropy enhances group cohesion but complicates group splitting. We construct a unified phase diagram for sheep behavior, identifying three regimes-fleeing, flocking, and grazing-based on group size and stimulus specificity. Increasing stimulus specificity shifts small group behavior from grazing to fleeing, while larger groups exhibit flocking. This transition underscores the challenge of controlling small indecisive collectives. Introducing the Indecisive Collective Algorithm (ICA), we show that deliberate indecisiveness and stochasticity improve control efficiency. ICA outperforms traditional averaging-based algorithms in high-noise settings and excels in tasks requiring group splitting. Our study offers a foundational framework for controlling small, indecisive groups, applicable to biochemical reactions, cell populations, and opinion dynamics.