Our computers add using really complex energy-consuming transistor circuits, but neurons just directly add their voltage inputs, because Maxwell's laws of electromagnetism already know how to add voltage.
Can AI Match the Human Brain? | Surya Ganguli | TED · TED
They found that if they had a vacuum tube like this one and applied a high voltage across it, something strange happened.
The case for curiosity-driven research | Suzie Sheehy
So when I wave my hand near the plates, you can see that the voltage changes just like the touchscreen responds to my hand.
How to spark your curiosity, scientifically | Nadya Mason