A headset for detecting brain electrical activity of a human subject comprising: a flexible substrate dimensioned to fit a forehead of the subject having a first end and a second end, wherein the first end and the second end each includes a securing device configured to engage an ear of the subject to position the substrate across the forehead, and wherein the substrate includes at least one expansible region permitting a distance between the first end and the second end to selectably vary; a plurality of electrodes disposed on the substrate wherein said plurality of electrodes are configured so that when the headset is positioned on the subject: a first electrode 408) contacts a top center region of the forehead, a second electrode contacts a lower center region of the forehead, a third electrode contacts a front right region of the forehead, a fourth electrode contacts a front left region of the forehead, a fifth electrode contacts a right side region of the forehead, and a sixth electrode contacts a left side region of the forehead; and wherein the headset further comprises one electrode disposed on each securing device and configured to contact an ear region of the subject when the headset is positioned on the subject; and flexible circuitry in the substrate operably coupled to each electrode, characterised in that at least the third electrode and the fourth electrode are independently movable in at least a vertical direction relative to the other electrodes when the headset is horizontally positioned on the subject. a flexible substrate dimensioned to fit a forehead of the subject having a first end and a second end, wherein the first end and the second end each includes a securing device configured to engage an ear of the subject to position the substrate across the forehead, and wherein the substrate includes at least one expansible region permitting a distance between the first end and the second end to selectably vary; a plurality of electrodes disposed on the substrate wherein said plurality of electrodes are configured so that when the headset is positioned on the subject: a first electrode 408) contacts a top center region of the forehead, a second electrode contacts a lower center region of the forehead, a third electrode contacts a front right region of the forehead, a fourth electrode contacts a front left region of the forehead, a fifth electrode contacts a right side region of the forehead, and a sixth electrode contacts a left side region of the forehead; and wherein the headset further comprises one electrode disposed on each securing device and configured to contact an ear region of the subject when the headset is positioned on the subject; and a first electrode 408) contacts a top center region of the forehead, a second electrode contacts a lower center region of the forehead, a third electrode contacts a front right region of the forehead, a fourth electrode contacts a front left region of the forehead, a fifth electrode contacts a right side region of the forehead, and a sixth electrode contacts a left side region of the forehead; and wherein the headset further comprises one electrode disposed on each securing device and configured to contact an ear region of the subject when the headset is positioned on the subject; and flexible circuitry in the substrate operably coupled to each electrode, characterised in that at least the third electrode and the fourth electrode are independently movable in at least a vertical direction relative to the other electrodes when the headset is horizontally positioned on the subject. <EOS>