The winds must be whispering again. A film based on Electronic Voice Phenomena is about to be released, and the excellent Mind Hacks site is talking about the balance between our bottom-up experience of the world and our top-down interpretation of it:
You can see your top-down processes at work best in situations where the bottom-up processes are weak. With vision this might be in the dark, or where you only glimpse something or someone for a fraction of a second. In hearing this might be where background noise is loud. Poor resolution, brief or noisy information tips the balance in favor of top-down information. What we see comes to reflect more of what we already know and what we expect. Hence we see things in the dark: our brains fill in what is most likely there, what might be there, or what we fear could be there, based on small clues from what actually is perceivable there.