The set-shift paradigm. Stimuli consisted of arrows that could appear in two different locations (left/right) and point in two different directions (up/down). The stimulus was presented on the screen for a maximum of 4,000 ms and was terminated upon a button press. Each response was immediately followed by a green (correct response) or red feedback (incorrect response) screen for 2,000 ms. The correct response depended on the relevant feature of the stimulus (i.e. location/direction). A red feedback screen following a correct response signaled a rule shift.