"Electrical potentials" refer to the small electrical fields produced by your brain cells. We can sense this activity by placing sensors on the scalp, then amplifying the small electrical potentials they pick up.  The scalp sensor is a piece of silver attached to a wire, which is then embedded in a piece of sponge in the end of a plastic tube. There are between 128 and 256 of these electrodes, which are sewn together in a geodesic pattern with elastic thread; this produces an electrode net. In order to detect the electrical potentials, the net is soaked in a slightly salty, soapy solution and then placed on your head. The salt conducts the small electric potentials effectively, while the soap helps dissolve the oil on your scalp to provide a clean contact. The wires of the net are connected to a computer through isolation amplifiers. Once we amplify and digitally record the brain waves on a computer, we can analyze the data in several ways. This analysis is completely anonymous: no one can connect your answers of your brain waves to your name, because all data are entered and recorded with code numbers.