Watch a rapid stream of letters. Most are O (standard). When you see an X (target), press Space or tap the button as fast as you can.
Very Easy
Slow stream (1 s), 25% targets, 30 trials.
Easy
Moderate pace (800 ms), 20% targets, 40 trials.
Medium
Standard pace (600 ms), 20% targets, 50 trials.
Hard
Fast stream (400 ms), 15% targets, 60 trials.
Expert
Very fast (250 ms), 15% targets, 70 trials — demands peak vigilance.
Scientific Background
Based on: P300 Oddball Paradigm (Sutton et al., 1965; Polich, 2007) (Sutton et al., 1965)