Figure 1.

General experimental design. The speeded interpolated task followed presentation of an auditory running memory span trial (12 – 20 random digits) or an ordinary memory span trial (6 random digits). The box flashed on either the right or left side at random. Feedback to accurate responses in the speeded task included reaction time on the current trial, mean reaction time for all trials so far in the block, and encouragement to beat the current response time on the next trial. Incorrect responses on the speeded task voided the trial, and a replacement trial with the same number of digit stimuli was added at random among the remaining trials.