The capacity of working memory has been suggested
to differ among people and these differences affect performance
in a wide variety of cognitive tasks. This study explored
electrophysiological correlates of individual differences
in working memory capacity by means of event-related potentials.
Thirty-four healthy students performed two- and five-choice
reaction time tasks. In the two-choice reaction time (2CRT)
task, two digits (3 and 7) were presented visually with
probabilities of .20 and .80. In the five-choice reaction
time (5CRT) task, five digits (3, 4, 5, 6, and 7) were
presented equiprobably in a random order. Participants
were required to press a button corresponding to each digit
with a different finger. Working memory capacity of each
participant was assessed by the reading span test originated
by M. Daneman and P.A. Carpenter (1980). Participants with
high reading span produced larger P300s than did persons
with low reading span in the 5CRT task, but the difference
was not significant in the 2CRT task. It had been suggested
that individual differences in working memory capacity
would affect initial stages of information processing as
early as 300 ms after stimulus onset.