RT Journal Article SR Electronic T1 Induction of Kanizsa contours requires awareness JF bioRxiv FD Cold Spring Harbor Laboratory SP 050526 DO 10.1101/050526 A1 Theodora Banica A1 Dietrich Samuel Schwarzkopf YR 2016 UL http://biorxiv.org/content/early/2016/04/27/050526.abstract AB It remains unknown to what extent the human visual system interprets information about complex scenes without conscious analysis. Here we used visual masking techniques to assess whether illusory contours (Kanizsa shapes) are perceived when the inducing context creating this illusion does not reach awareness. In experiment 1 we tested perception directly by having participants discriminate the orientation of an illusory contour. In experiment 2, we probed perception indirectly by using Kanizsa shapes to prime performance on a visual search task. In experiment 3, we exploited the fact that the presence of an illusory contour enhances performance on a spatial localization task. Moreover, in experiment 3 we also used a different masking method to rule out the effect of stimulus duration. Our results suggest that participants do not perceive illusory contours when they are unaware of the inducing context. While perceptual grouping and surface segmentation may occur without awareness of the stimuli, the induction of the phenomenal percept of an illusory shape does not. This is consistent with theories of a multistage, recurrent process of perceptual integration. Our findings thus challenge some reports, including those from neurophysiological experiments in anaesthetized animals. We discuss the importance to test the presence of the phenomenal percept directly with appropriate methods.