A feedback display was presented after a varying ISI of 900 to 1300 ms. In potential-reward trials, four cents could be won or lost, indicated by a display above the standard fixation square of ‘+4’ after correct and fast responses and ‘−4’ after incorrect or too-slow responses. To preserve trial structure similarity, in no-reward trials feedback comprised of a ‘+0’ or ‘−0’ for correct and incorrect/missed trials, respectively. The feedback stimulus was displayed for 400 ms, followed by an inter-trial interval of 600–1000 ms. Additionally, after each experimental run the total gained amount was presented.
