In his magisterial Principles of Psychology (1890), William James speculated that the same brain regions might be used both when looking at an object and when imagining it. That was confirmed by LeBihan and colleagues in 1986. They used functional magnetic resonance imaging (fMRI) to track blood flow in the region of the brain known to be involved in the early processing of vision (the primary visual cortex, at the very back of the brain). When their subjects looked at a picture, there was increased blood flow (indicating increased brain activity) in the visual cortex (but not in a control area that was involved in vision). That was hardly surprising--it is the visual cortex, after all. But when they then asked their subjects to imagine the same picture there was a similar--though slightly weaker--activation of the same region. This showed that James was right--when we imagine a scene we use the same brain regions that are used in actual vision.