An electrode cap contains at least one electrode array and is to be applied to a subject's head. The electrode array contains an insulating layer, two electrodes disposed opposite one another on the insulating layer, namely a first measurement electrode facing toward the subject's head and a reference electrode facing away from the subject's head. A conductive body abuts the reference electrode and is in electrical contact therewith, and is arranged on the side of the reference electrode that faces away from the subject's head. The individual conductive bodies of all the electrode arrays are electrically connected to each other.