Many studies have shown that physical responses including heart rate, pupil dilation and brain activity change between one and 10 seconds before people see a scary image (like a slithering snake). In most of these experiments, frightening pictures were randomly interspersed with more-neutral ones, so that in theory participants didn’t have any clues about which photo would pop up next. But because the finding seemed so unnatural, those studies were understandably met with skepticism.

To see whether the effect was real, Mossbridge and her team analyzed over two dozen of these studies. As part of the analysis, they threw out any experiments in which they saw bias or flaws.

They still found a “presentiment” effect, in which measures of physiological excitement changed seconds before an event. The finding suggests that people’s bodies subconsciously sense the future when something important is about to happen, even if the people don’t know it.