A glimpse of swimmers could lead to advances in robotics

The constant movements of fish that seem random are precisely deployed to provide them at all times with the best sensory feedback they need to navigate the world, found researchers at Johns Hopkins University.

The discovery, published today in the journal Current biology, improves our understanding of the active detection behaviors practiced by all animals, including humans, such as badping, touching and sniffing. It also shows how robots built with better sensors could interact more effectively with their environment.

"In biology, we say that when the world is still, we can not feel it anymore," says Noah Cowan, lead author and mechanical and robotics engineer at Johns Hopkins. "You have to move actively to perceive your world, but we have found that what was previously unknown is that animals constantly regulate these movements to optimize sensory inputs."

For humans, active detection involves touching the bathroom light in the dark or swinging an object up and down in our hands to determine its weight. We do these things almost unconsciously, and scientists know very little about how and why we adjust our movements based on the sensory feedback we receive from them.

To answer the question, Cowan and his colleagues studied fish that generate a weak electric field around their bodies to help them with communication and navigation. The team created an augmented reality for the fish to allow them to observe the evolution of the fish movements according to the reactions of the environment.

Inside the tank, the weakly electric fish floated in a tube where they squirmed constantly to maintain a constant level of sensory information about their environment. The researchers first altered the environment by moving the tube in a manner synchronized with the movements of the fish, making it more difficult for the fish to extract the same amount of information as it did. he had received. Then the researchers moved the tube in the opposite direction to the fish, making it easier. In each case, the fish immediately increased or decreased their swim to ensure that they received the same amount of information. They swam further when the movement of the tube gave them less sensory feedback and they swam less when they could get more back with less effort. The results were even more pronounced in the dark, when the fish had to rely more on their electrical sense.

"Their actions to perceive their world are subject to constant regulation," said Eric Fortune of the New Jersey Institute of Technology, co-author of the study. "We think it's just as true for humans."

Since Cowan is a robotologist and most of the authors of this team are engineers, they hope to use biological knowledge to build robots with smarter sensors. Sensors are rarely a key part of robot design now, but these results made Cowan understand that they should perhaps be.

"Surprisingly, engineers generally do not design systems operating in this way," says Debojyoti Biswas, a graduate student of Johns Hopkins and senior author of the study. "Learning more about how these tiny movements work could provide new design strategies for our smart devices to see the world."

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Note: A short video of weakly electric fish available here

Other authors include Luke A. Arend, Johns Hopkins undergraduate researcher; Sarah A. Stamper, Johns Hopkins Postdoctoral Fellow; Balázs P. Vágvölgyi, Associate Research Engineer Johns Hopkins; and Fortune, badociate professor at the New Jersey Institute of Technology.

This work was funded by the James McDonnell Foundation's Complex Systems Research Grant 112836; National Science Foundation Collaborative Award, Fellowships 1557895 and 1557858 and National Science Foundation Grant Research Experiences for Undergraduates (1460674).

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