Figure 1.

Experiment 1 trial sequence. (A) Schematic for exogenous attention condition. Observers discriminated clockwise (+45°) versus counterclockwise (−45°) tilts of a sinusoidal grating presented with one of six spatial frequencies (0.5–11 cpd) at four possible eccentricities (0°, 3°, 6°, 12°). Grating contrast was manipulated via the method of constant stimuli. Precues directed attention to a specific location (Valid) or distributed attention across the visual field (Neutral). Observers were seated 79 cm away from the display, and their eyes were tracked to ensure stable fixation. The horizontal black line was not displayed during the experiment. (B) Schematic for endogenous attention condition. Duplicate timing information was omitted from B.