An adhesive-mountable head-wearable EEG apparatus is disclosed. The apparatus includes an EEG sensor for acquiring an EEG signal of a wearer, a central processing unit for receiving the EEG signal, a small circuit board including the EEG sensor and the central processing unit, and a compact enclosing shell for enclosing the small circuit board, the EEG sensor, and the central processing unit. An adhesive electrode assembly attaches to the compact enclosing shell, or to the small circuit board within the enclosing shell, via snaps or magnets. The adhesive electrode assembly includes two or more gel electrodes for acquiring an EEG signal, and for adhering to the forehead so as to wearably support the EEG apparatus on the forehead. The compact enclosing shell includes chamfered edges, and is sized so as to reduce lateral forces on the compact shell that would tend to detach the EEG apparatus from the wearers forehead.
