Abstract: Transdermal electrical stimulation (TES) applicators that are wearable and configured to attached to a subject's pinna (ear) and adapted to apply TES to modulate the subject's cognitive and/or physiological state. These apparatuses may be configured so that they can be worn against the ear (e.g., the cymba of the ear) to deliver TES. Also described herein are methods of using them to modulate a subject's cognitive state. These TES applicators may also be adapted to function as audio headphones for concurrent delivery of TES and audible signals (e.g., music).