richard_dawkins_-_the_god_delusion

90 T H E C, O D D E L U S I O N
make sense of the optical data when a hollow mask rotates while
being perceived to be a solid mask. 48 It is like the illusion of a
rotating radar dish that you sometimes see at airports. Until the
brain flips to the correct model of the radar dish, an incorrect
model is seen rotating in the wrong direction but in a weirdly cockeyed
way.
I say all this just to demonstrate the formidable power of the
brain's simulation software. It is well capable of constructing
'visions' and 'visitations' of the utmost veridical power. To simulate
a ghost or an angel or a Virgin Mary would be child's play to software
of this sophistication. And the same thing works for hearing.
When we hear a sound, it is not faithfully transported up the
auditory nerve and relayed to the brain as if by a high-fidelity Bang
and Olufsen. As with vision, the brain constructs a sound model,
based upon continuously updated auditory nerve data. That is why
we hear a trumpet blast as a single note, rather than as the composite
of pure-tone harmonics that gives it its brassy snarl. A
clarinet playing the same note sounds 'woody', and an oboe sounds
'reedy', because of different balances of harmonics. If you carefully
manipulate a sound synthesizer to bring in the separate harmonics
one by one, the brain hears them as a combination of pure tones for
a short while, until its simulation software 'gets it', and from then
on we experience only a single note of pure trumpet or oboe or
whatever it is. The vowels and consonants of speech are constructed
in the brain in the same kind of way, and so, at another
level, are higher-order phonemes and words.
Once, as a child, I heard a ghost: a male voice murmuring, as if
in recitation or prayer. I could almost, but not quite, make out the
words, which seemed to have a serious, solemn timbre. I had been
told stories of priest holes in ancient houses, and I was a little
frightened. But I got out of bed and crept up on the source of the
sound. As I got closer, it grew louder, and then suddenly it 'flipped'
inside my head. I was now close enough to discern what it really
was. The wind, gusting through the keyhole, was creating sounds
which the simulation software in my brain had used to construct a
model of male speech, solemnly intoned. Had I been a more impressionable
child, it is possible that I would have 'heard' not just
unintelligible speech but particular words and even sentences. And