Figure 1.

Experimental paradigm and behavioral results. (A) Example images used in the experiment, with different levels of noise. (B) Each block consisted of two phases: in the first phase, half of the images are familiarized. In the second phase, images are degraded and shown briefly. Images from phase 1 are presented together with new images (manipulation of prior knowledge). Familiar and unfamiliar images are also shown at two different degradation levels (i.e. high and low degradation; manipulation of sensory evidence). On a few trials an image without a person is presented (catch trials). Each image is followed by an objective and a subjective question. On some trials a third question (Was this picture presented in phase 1?) is also asked. (C) Behavioral results. Both prior knowledge and sensory evidence enhance perception. Effects are shown for both the objective discrimination data and the subjective reports about visibility.