1. Scientists at the University of Melbourne got 10 people to take a test to see if they could identify a change in a person’s appearance.
A photograph (like above) flashed up for 1.5 seconds before a 1 second break, then another image of the same person appeared for 1.5 second. The participants were asked if there was a change in the photograph and, if they thought there was, to identify it from a list of options. Each participant did this 140 times.
2. The participants were all good at realising when something had changed, but struggled to identify what exactly had changed.
Follow up experiments showed that participants were probably subconsciously noticing a difference in the “scene statistics” of the image. For example, they might notice that the amounts of red and green in the image changed but not be able to identify which part of the image had changed.