It's very clever. The brain fills in the blanks like an illusion. Did you know that when we turn our head/eyes from left to right, the brain takes a snapshot at the left, middle and right. The brain then interprates and fills in the blanks, a bit like stop frame animation. This all happens so quick we don't even realise it, and explains why our vision remains stable and is not all jumpy like hand holding a video camera and panning. I learnt that from watching the Royal Institute of Christmas Lectures. It surprised me and explains how things can be mis-interprated. So yeh it's our dirty minds working overtime.
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