humidity (above 80%). Odors were presented in four blocks of 24 trials each, with a variable interstimulus interval (15–25 s). White noise of approximately 75 dB SPL was presented binaurally via Telephonics TDH–49P earphones to preclude hearing the switching valves. Participants responded as to whether they perceived a low or high intensity odor by raising their left or right hand, which was visually monitored and recorded by the experimenter. Therefore, the present paradigm consisted of an active odor intensity detection task, requiring conscious processing of and responding to perceived hydrogen sulfide stimuli. Because the time of odor stimulation was not cued, participants could fail to respond (miss). Nostril order and response hand assignment were counterbalanced across blocks and participants.
