For example, if a 9 months old baby hears someone referring to an object by an incorrect name (e. g. calling a cat a ball), and gets surprised, a group of neurons gives a specific signal that something unusual and unexpected happened, and this signal can be recorded with a special device. Such EEG patterns let us infer what babies understand from the world around them. Before the session we put a soft net cap on babies’ head that is designed specifically for infants and is widely and safely used in numerous institutions around the world. This net measures the weak electrical signals coming from neurons, just like a thermometer measures body temperature. During EEG studies we usually show babies short videos or pictures on a screen. We record the whole session on video for later analysis.