The study builds on the procedure outlined in our previous OERP report (Kayser et al., 2010). Participants were seated in an IAC (Industrial Acoustics Company) sound-attenuated booth using a chin and forehead rest, with a video camera monitoring participants’ compliance and behavior. They were instructed to focus on a monitor that presented visual cues signaling the interval when an odor may be present and when to respond, and to keep breathing normally through the nose but not the mouth (velopharyngeal closure as an active breathing technique was not incorporated; cf. footnote 2 in Kayser et al., 2010; Seubert et al., 2013). H2S stimuli (10 ppm, Scott Speciality Gases, Plumsteadville, PA) at strong (undiluted), medium (diluted to 70%) or weak (diluted to 40%) concentrations or blank air were delivered to the left or right nostril by a constant-flow olfactometer (OM2s, Heinrich Burghart GmbH, Wedel, Germany) through a Teflon™ tube inserted approximately 1 cm into the naris. Stimulus duration was 200 ms (not more than 50 ms rise time according to manufacturer specification). For any given session, the air stream at the
