By hooking up a dead fish to an isolated electric current, the researchers were able to make that fish twitch, seemingly in response to the eel's electrical impulses. But when the eel approached, they switched off the current, and sent a charge through a carbon rod instead. Instead of going for the tasty fish, the eel immediately switched gears and grabbed the rod instead. Other experiments included passing a charge through varying points and seeing how the eel responded--the eel ended up attacking the charge. The researchers also found that when there was no electrical current present, the eel didn't strike.