ERP stands for event-related potential. As your brain works, it generates electrical potentials. By placing tiny electrodes near the scalp, we can record changes in this potential in response to events in the world. In our studies, we show infants pictures or play sounds for them. They wear a small cap with electrodes sewn into it so that we can observe how their brain responds to the stimuli. In this way, we are able to learn about what parts of the infant brain are involved in processing number.