Fig. 1.

General experimental protocol. Left shows the stimulus presentation timeline as it was physically presented on the screen; Right illustrates a subject's perception of the presented stimuli. The blue-shaded region highlights the unconscious portion of the trial. The mask consisted of colored dots spinning concentrically around the central fixation point at a rate of 1.67 revolutions per second. The dot motion stimulus consisted of a number of randomly moving dots, with a fraction of the dots (10–60%) moving coherently in one of two directions. At stimulus offset, a tone was sounded to prompt participants to report the direction of motion as quickly and accurately as possible. Participants had a response window of 1,000 ms in which to make their choice. After their response, the fixation point changed color. Participants were then asked to indicate whether they saw any part of the dot motion stimulus during the first one-half of the stimulus presentation (when it was presented concurrently with the mask stimulus; 1 = saw part/all of the stimulus; 2 = stimulus was completely suppressed for the entire duration).