Abstract: A device for determining a physiological or psychological state of a mammal is disclosed. The device has at least one earpiece with a main body having a body of revolution with an axis of revolution, and an endpiece configured to be inserted into an ear canal. The endpiece has a cylindrical channel intended to receive a body of revolution for detachably mounting the endpiece on the main body, the endpiece being arranged to be movable in rotation about the axis of revolution in order to allow at least one electrode to be oriented toward a zone of the brain of the mammal, and the endpiece having a plurality of electrodes arranged on an outer surface of the endpiece, each electrode being configured to pick up an electrical signal in the ear canal of the mammal.