PNAS 115, 6852–6857 (2018).

Though less shocking than the electric eel, mormyrids are weakly electric fishes that survey their environment and communicate through electrical discharges from a specially evolved organ. Mormyrids will often sync up their electrical activity, but how and why was unclear, at least while limited to animal observations. To prompt the electrical echoes for further study, researchers created a robotic version that they could control. Real fish ignored the artificial animal if it remained silent but engaged with it when it emitted electrical discharges.

Regardless of how random the electrical stream, the fish would eventually start to echo the robot. Vocal imitation is considered a sign of cognitive ability—observing such a pattern could be sign of a similar, if simple, mechanism in a novel form.