Cued Posner spatial attention task. The subject attends to the small fixation cross at the center of the screen, with a box to either side. As a cue, one of the boxes is highlighted in red color. A large target cross appears inside one of the boxes (with 1000 ms S1–S2 inter-stimulus interval), and the test subject indicates which box by pressing a button with the corresponding hand. In 80 % of trials, the target cross will appear in the box cued in prior step (valid cue, congruent), while 20 % of the time it will appear in the other box (invalid cue, incongruent). The horizontal condition is shown at the left, while diagonal condition at the right.