An auditory novelty oddball task was implemented on a Neuroscan STIM system using stimuli developed for this task (Friedman et al., 1993). For each subject, eight blocks of 50 trials consisting of two 300-ms tones were presented in pseudorandom order (1000 ms stimulus onset asynchrony; 10 ms rise and fall time). A nontarget tone of 350 Hz was presented to the subjects frequently (p = .76), as well as an infrequent target tone (p = .12) of 500 Hz. Novel sounds (i.e., animal sounds, musical instruments, environmental sounds) with durations of 100–400 ms were infrequently (p = .12) intermixed with the nontarget and target tones. All stimuli were presented binaurally over headphones at 85 dB SPL. Subjects were instructed to focus their eyes on a fixation cross displayed on a computer monitor, and to respond with a button press as quickly as possible when, and only when, they heard the infrequent target tone. Response hand (right or left) was counterbalanced across blocks, and will not be considered further in this report.
