A headset comprising: (i) a front portion comprising a first end, a second end, a sensing bar , and a locator bar , wherein the sensing bar and the locator bar are joined at the first end and the second end of the front portion and comprising a space below the sensing bar and above the locator bar between the first end and the second end, wherein (a) the maximum outer distance between the top of the locator bar and the bottom the sensing bar is 40±2 mm, 42±2 mm or 44±2 mm, (b) the sensing bar is shaped and configured to contact the forehead of a user wearing the headset and comprises a first electrical sensor for measuring electroencephalography (EEG) signals positioned to contact the forehead of the user at about position AF3, the first electrical sensor for measuring EEG signals comprising one or more electrodes, and a second electrical sensor for measuring EEG signals positioned to contact the forehead of the user at about position AF4, the second electrical sensor for measuring EEG signals comprising one or more electrodes, and (c) the locator bar is shaped and configured to rest upon the brow of the user to stabilize the headset and has a slight crease in the center of the locator bar to enable proper positioning of the headset on the forehead; and (ii) a first side portion and a second side portion , the first side portion joined to the first end of the front portion and the second side portion joined to the second end of the front portion, wherein the first side portion , the second side portion , and the front portion, together, are shaped and configured to grip the head of the user. (i) a front portion comprising a first end, a second end, a sensing bar , and a locator bar , wherein the sensing bar and the locator bar are joined at the first end and the second end of the front portion and comprising a space below the sensing bar and above the locator bar between the first end and the second end, wherein (a) the maximum outer distance between the top of the locator bar and the bottom the sensing bar is 40±2 mm, 42±2 mm or 44±2 mm, (b) the sensing bar is shaped and configured to contact the forehead of a user wearing the headset and comprises a first electrical sensor for measuring electroencephalography (EEG) signals positioned to contact the forehead of the user at about position AF3, the first electrical sensor for measuring EEG signals comprising one or more electrodes, and a second electrical sensor for measuring EEG signals positioned to contact the forehead of the user at about position AF4, the second electrical sensor for measuring EEG signals comprising one or more electrodes, and (c) the locator bar is shaped and configured to rest upon the brow of the user to stabilize the headset and has a slight crease in the center of the locator bar to enable proper positioning of the headset on the forehead; and (ii) a first side portion and a second side portion , the first side portion joined to the first end of the front portion and the second side portion joined to the second end of the front portion, wherein the first side portion , the second side portion , and the front portion, together, are shaped and configured to grip the head of the user. <EOS>