The sequence and timing of events on a trial. On each trial of the experimental task, subjects first fixated on a “+” at the center of a computer screen for 750 msec. After this, each of the study items was presented for 750 msec with a 300-msec interval, during which a blank screen was presented. After the last item from a list was presented, a short beep sounded, and an ellipsis (…) was displayed for a 300-msec retention interval, indicating that the subject should wait for the probe. This was followed by the display of the probe for 750 msec. The trial ended when the subject responded by pressing either of two predesignated keys. Feedback was provided using distinctive tones that indicated whether their response had been correct or incorrect. Between trials, the screen indicated the percentage of correct trials.