Fig. 3 |. Experiment 2.

Observers were tested with three tasks in different sessions: the presaccadic attention (PSA) task, covert endogenous attention (ENDO) task and covert exogenous attention (EXO) task. a, Here we illustrate the procedures of the PSA task and the ENDO task together as they shared a similar stimulus sequence. The cue-to-target SOA was shorter in the PSA task than in the ENDO task. Two stimuli, a target and a distractor, were presented simultaneously. In the PSA task, the precue instructed observers to saccade to the cued location. In the saccade towards condition, the precue matched the target location, whereas in the saccade away condition, the precue indicated the distractor. Saccade towards and saccade away conditions were interleaved with equal probability; therefore, the saccade cue was uninformative regarding the target location. In the ENDO task, observers maintained fixation throughout the trials and the precue instructed observers to covertly pay attention to the cued location. The valid and invalid trials were interleaved within the blocks with a 70 and 30% probability, respectively; thus, the precue was informative regarding the target location. At the end of a trial, observers reported the orientation of the target probed by the auditory response cue (high tone, target at the right; low tone, target at the left). b, In the EXO task, the precue was a brief flash. In the neutral condition, the precue was presented at the fixation. In the valid condition, the precue was flashed above the target whereas in the invalid condition, the precue was flashed above the distractor. The valid and the invalid trials were interleaved with equal probability, hence, the precue was uninformative regarding the target location. See details in the Methods.