Unconscious intuitive physics: Prioritized breakthrough into visual awareness for physically unstable block towers

A central goal of perception and cognition is to predict how events in our local environments are likely to unfold: what is about to happen? And of course some of the most reliable ways of answering this question involve considering the regularities of physics. Accordingly, a great deal of recent research throughout cognitive science has explored the nature of ‘intuitive physics’. The vast majority of this work, however, has involved higher-level reasoning, rather than seeing itself—as when people are asked to deliberate about how objects might move, in response to explicit questions (“Will it fall?”). Here, in contrast, we ask whether the apprehension of certain physical properties of scenes might also occur *unconsciously*, during simple passive viewing. Moreover, we ask whether certain physical regularities are not just processed, but also visually *prioritized*—as when a tower is about to fall. Observers viewed block towers—some stable, some unstable—defined in terms of whether they would collapse as a result of external physical forces (such as gravity) alone. We used continuous flash suppression (CFS) to render the towers initially invisible: observers viewed them monocularly through a mirror haploscope, while a dynamic Mondrian mask was presented to their other eye. We then measured how long towers took to break through this interocular suppression, as observers indicated when they became visually aware of anything other than the mask. The results were clear and striking: unstable towers broke into visual awareness faster than stable towers. And this held even while controlling for other visual properties—e.g. while contrasting pairs of stable vs. unstable towers sharing the same convex hull, and differing only in the horizontal placement of a single block. This work shows how physical instability is both detected and prioritized, not only during overt deliberation, but also in unconscious visual processing.