Study design and mean reaction times.

<p>A. Mean reaction times of 60 and 50 trials. The figure shows average reaction times of groups of 60 sequential trials and the last 50 random trials during each of the four testing blocks for younger and older subjects. Means of 60 are labeled “S” and means of 50 are labeled “R”. B. Serial Reaction Time Task (SRTT) design. The task was performed over four blocks, here labeled as test, training, test, and retest. The first three blocks of the task are completed during session 1, and the fourth block is completed during session 2. Each block begins and ends with 50 random trials (grey areas labeled “R”) sandwiching 180 or 300 sequence trials (white areas labeled “S”). A subject's skill at any given block is measured by subtracting the mean of the last 50 sequence trials from the mean of the last 50 random trials. Skill at the end of session 1, or block 3, is shown. The change in skill from session 1 to session 2 (“delta skill” or “off-line learning”) is found by subtracting skill at session 1 (Skill 1) from skill at session 2 (Skill 2). Error bars represent standard error of the mean.