Illustrations of the three tasks. Actual stimuli were presented on a black background. Filled black rectangles correspond to red, outlined rectangles correspond to green, and the digital 2s and 5s were white. On the left, the target was a red vertical rectangle among green vertical rectangles (feature search). In the middle, the target was a red vertical rectangle among green vertical and red horizontal rectangles (conjunction search). On the right, the target was a digital 2 among digital 5s (spatial configuration search).