Virtual Reality Shows Glassfish Copy One Neighbor to School Together

Tiny glassfish may coordinate their schooling through a surprisingly selective process: copying the movement of one nearby neighbor rather than calculating the average direction of the group. Researchers at the University of California San Diego studied micro glassfish, or Danionella cerebrum, to investigate how individual decisions produce the synchronized motion seen in fish schools. Their findings, published in Physical Review Letters, describe a computational model in which each fish selects a nearby neighbor and copies its movement direction. That mechanism differs from a long-standing model of collective behavior, which assumes that an animal aligns with the average direction of others in its surroundings. According to the study, the one-neighbor approach produces more dynamic group behavior and can explain how schools form and break apart across different developmental stages. The researchers tested the model using virtual-reality “fish.” When programmed virtual fish changed direction, real glassfish responded in ways that matched the predictions of the pairwise-copying model, Phys.org reported. The experiment also helped identify when these interactions occur. Glassfish move in alternating bursts and glides. A burst includes acceleration and turning, while a glide involves deceleration and more linear movement. The researchers found that the end of one fish’s turn creates a brief opportunity for nearby fish to align with it. Mature glassfish were observed making these copying turns with fast reaction times. The result provides a more detailed, turn-by-turn account of how fish respond to one another, rather than treating the school as a single coordinated unit. The study was led by Palka Puri, a recent UC San Diego physics doctoral graduate, with associate professor Johnatan Aljadeff and assistant professor Matthew Lovett-Barron. The researchers say the findings could help connect models of group movement with the sensory and motor processes taking place inside individual animals. Because Danionella fish are transparent, their brains can be observed using brain-wide neural imaging. The researchers hope the newly identified timing of social copying will help them investigate how individual fish detect a partner’s movement, decide when to respond, and contribute to collective behavior.