In calm water, the route is clear. But in turbulent flows, a robot needs a different strategy. Typical approaches demand an accurate map of currents, but in reality, you can't get one. Nature does it differently: fish feel pressure and vortices right against their bodies.
In a virtual turbulent flow, researchers trained robots to reach a target, equipping them with different “senses.” Some knew the direction to the target, others measured local water speed or its rotation (vorticity). Some remembered the last few measurements to account for the recent history of jolts, like a swimmer who remembers which way they were pushed a second ago.
The paradox: robots with rotation sensors reached the target more accurately, while speed-sensitive ones conserved energy. But give the robot an overall picture of the currents, and its skills collapsed. Too much information was confusing, whereas a modest local memory provided a reliable course.
The lateral line of fish not only replaces a whole set of sensors but also works without the brain: it's a reflex that lets them instantly dodge predators.