From Swarm to Individual: Emergent Individuality in Light‐Mediated Robot Collectives

Collective behavior is often modeled as the outcome of interactions among similar agents, while variation among individuals is commonly treated as a property that agents bring into the group. Here, we take a complementary view: Individual differences can also be produced, amplified, or reorganized by the collective conditions in which agents interact. We tested this idea using phototactic robots under global light and robot‐mounted local light cues. The robots shared the same controller and sensorimotor design, but they retained small physical differences that affected their motion. Global light increased inter‐individual behavioral‐state differentiation, whereas local light cues reduced these differences. Within trials, the light environment modulated the prevalence of both milling‐dominant and high‐switching robots. These results show that light‐mediated collective conditions changed not only how strongly robots differed from one another, but also what kinds of behavioral profiles appeared within the group. This system provides a simple physical platform for studying how environmental structure, local interaction, and embodied variability shape behavioral differentiation in collectives.