As noted by the authors, many lines of investigation have converged in recent years to frame the nature and problem of consciousness; studies of perceptual priming where the main effect is mediated nonconsciously; studies of reversible figures (for example, Necker's cube
) in which the visual experience is altered without any direct and conscious effort by the percipient; studies of hallucinatory experiences, of dreams, of stimulus saliency.
You've seen, for example, the Necker's cube
? When I show it to my students, they always see the initial kinds of variations, tilting left, tilting right.
Free Will and Necker's Cube
: Reason, Language and Top-Down Control in Cognitive Neuroscience, GRANT GILLETT and SAM C.