Fig. 1.

Experimental procedure. a Time course of a single trial. An initial fixation cross was presented. Then a brief cue appeared, to remind the participant of the hazard rate condition (high vs. low). The fixation cross then reappeared in a variable foreperiod before the single target letter was presented either above (as shown) or below the fixation cross before being masked. The participant then reported the letter identity if known. b Foreperiod distributions. These were defined to be geometric and such that, in the high hazard rate condition the expected foreperiod was 0.75 s, and in the low hazard rate condition it was 4.5 s