Figure 1 |. Distributed spatial attention task.

Each trial begins with the presentation of a centrally presented spatial cue (left) overlaid on top of a persistent central fixation cross. The cue indicates (with a green wedge) where an upcoming target will appear, with varying certainty, after a random length preparatory period. In the 100% certain condition (top) the target will briefly (50 ms) appear exactly 4.5° to the left or to the right of center (right). In the 75% certainty condition, the target will appear anywhere in a 90° arc, with 4.5° central eccentricity. In the 50% certainty condition, the target will appear anywhere in a 180° arc, while in the 0% certainty condition the target will appear anywhere in the full 4.5° central eccentricity circle. Possible target locations are illustrated with the blue arc (not actually shown on screen). For the bilateral task variant, simultaneous to the presentation of the target a non-target stimulus with matched visual properties is always shown in the non-target hemifield, mirrored across the vertical meridian.