Implicit processing of surprising complexity and persistence was shown in a negative priming experiment (DeSchepper & Treisman, 1996). We found a slight delay in responding to novel, previously unattended nonsense shapes when they subsequently became relevant, even though explicit recognition memory was at chance (see Figure 6). This negative priming, which sometimes lasted for days or weeks, was established in a single trial and was specific enough to give at least partial discrimination between 260 different unfamiliar shapes.