Figure 1.

Diagram of the auditory short-term memory task. Each trial consisted of 500-ms sample and test sounds separated by a 5-s retention interval. For match trials, the sounds were identical and the correct response was a button press, whereas for non-match trials the sounds were non-identical and the correct response was to withhold from pressing the button. Sample and test sounds were pseudorandomly selected for each trial from a variety of naturalistic and artificial sound exemplars (see Methods). A pre-response wait period followed the test stimulus, after which the response button was illuminated to signal the response window. Responses outside of the response window (e.g., during the sound presentations or wait period) aborted the trial and these trials were not included in subsequent analyses. Overhead lighting provided constant low-level illumination throughout the session, and a second overhead light was turned on during the ITI to serve as a cue by which trials could be segregated.