Fig. 1

Paradigm. (A) The experiment started with a prestimulus period where only a dark grey screen was shown (for 600–800 ms). Afterwards, a fixation cross was presented for 1000 ms. Within these 1000 ms, additionally a subliminal stimulus was shown for 16.6 ms (one frame) at random positions between 312 and 600 ms before the test stimulus. The subliminal stimulus consisted of a ring around the fixation cross (visual angle 0.8°). Its grey value was adjusted to the perception level of the participant. Next, the two test stimuli were shown for 16.6 ms, each with a varying stimulus offset asynchrony (SOA) (see B for SOA condition). A poststimulus period followed, where a fixation cross was shown for 600 ms up to 1200 ms. Then the first and second response prompt followed (each could be displayed for up to 4000 ms). (B) The different SOA condition used in this experiment. The threshold SOA was individually defined to achieve 50% accuracy. (C) An example of a fully integrated test stimulus.