Figure 1.

Stimuli and trial timing of the masked Go/No-Go task and the control experiment. The gray circle and black cross duration was 16.7 ms. Go signal duration was 100 ms. In conscious No-Go trials, the SOA between the No-Go signal and the Go signal was 83 ms. Participants had to respond to the Go signal (black metacontrast mask) but were instructed to withhold their response when a No-Go signal preceded the Go signal. In the masked Go/No-Go task, a gray circle served as a No-Go signal, whereas in the control experiment, the No-Go signal was a black cross. Therefore, the masked gray circle was associated with inhibition in the masked Go/No-Go task and thus served as an unconscious No-Go signal. In the control experiment, the unconscious gray circle was not associated with inhibition (and was task irrelevant) because participants were instructed to inhibit their responses on a black cross. Comparing processing of unconscious gray circles between both experiments enabled us to test whether (1) high-level inhibitory control processes can be triggered unconsciously, (2) unconscious No-Go signals reach prefrontal areas, and (3) task relevance influences the depth of processing of unconscious stimuli.