These fish generate electric pulses to communicate with other fish and sense their surroundings. Some species broadcast shorter electric pulses, while others send out long ones. But all that zip-zapping in the water can get confusing.

The fish need to filter out their own pulses so they can identify external messages and only respond to those signals.

The solution to this problem is a brain function called a corollary discharge. It’s sort of like a negative copy of the original message—something that tells the fish, “Ignore this.”