Embodiments relate to devices for detecting electrical potentials corresponding to biological signals. The device comprises a flexible member for positioning over a forehead area of a human head and first, second and third electrodes located on the flexible member. The first electrode is located in a projecting portion of the flexible member to be positioned adjacent a nasion area of the head. The second electrode is to be positioned over a first lateral forehead area. The third electrode is to be positioned over a second lateral forehead area opposite the first lateral forehead area.