If you ever felt paranoid about subliminal messages, you might be right to worry. Images we see but don’t consciously register have been shown to inform people’s decision-making. Joel Voss of Northwestern University in Evanston, Illinois, and colleagues showed volunteers 12 kaleidoscope images for 2 seconds each while they also performed an unrelated number task to distract them from consciously committing the images to memory. A minute later, volunteers were asked to look at pairs of similar-looking images and choose the one they had seen before. They were also asked whether they were sure, had “a feeling” they were right, or were just guessing. Those who took a shot in the dark were as successful as the rest. “They were 70 to 80 per cent accurate; it would be only 50 per cent if it was chance,” says Voss (Nature Neuroscience, DOI: 10.1038/nn.2260). During the memory task, the volunteers’ brain activity was monitored by electrical sensors attached to their heads. As the pattern of activity differed between “guessers” and the other groups, it suggests that we access unconscious and conscious visual memories differently, says Voss. Issue 2695 of New Scientist magazine