  In cases of so-called ‘backward masking’, if two stimuli are presented in rapid succession, most subjects will be able to identify the second (and later) stimulus far more reliably than the first. In the particular experiment Dennett describes, the target stimulus is a solid disk, shown for 30 msec, and the mask – shown immediately afterwards – is a larger surrounding circle. Although subjects are shown both images, when queried they report that they saw just one: the circle. The standard interpretation of this sort of experiment, according to Dennett, is that in such cases the subject do not experience the target stimulus: they have no visual experience of the disk, the occurrence of the masking stimulus somehow interferes with the normal perceptual process. However, as he also notes, there is a second possible interpretation of the subject’s responses. Perhaps the subjects do experience the disk, but something interferes with their memory of this experience, and so when subsequently queried they deny having seen it. Dennett labels the first mechanism Stalinesque: since the experiences our perceptual systems produce do not accurately reflect the stimuli, there is a sense in which they are putting on a false and misleading display, in a manner (somewhat) reminiscent of Stalin’s show-trials. He calls the second mechanism Orwellian: a false and misleading version of recent events is being created by the subjects’ memories, and so history is being rewritten, in a manner (somewhat) reminiscent of Orwell’s 1984.