December 12th: The Fovea
Christmas. There’s a lot more that goes into it than one
person can feasibly experience. The amount of preparation involved in acquiring
gifts, all that food to get, cook, and give to people who may well be too
intoxicated to recognise what it is they’re consuming. The decorations, the work scheduling to get
it all organised, the arrangements, the visits. A lot of effort by one part,
which may be experienced as nothing more than a brief visit and an exchange of pointless
Christmas cards by another party. It’s tragic, in a way.
And that’s just on a small-scale, individual family basis. What
about the industrial processes that go into the whole festive season? Christmas
seems to have a profound effect on the whole economy, it’s reported in the
news, with constant update son how the high-street is doing. And think of the manpower
that goes into converting every branch of every multinational into a more ‘festive’
style. Even the fictional aspects, the Santa and his elves thing, if that were
true, it would involve countless hours of manual (‘elf’ual?) labour and the
violation of spacetime by a bearded fat man; and for what? This herculean effort
is experienced by individual children as a period of excitement and the
acquisition of a few more flimsy toys. Is that really all it amounts to?
This shouldn’t be surprise though, seeing as humans experience
such a thing on a regular basis. Our own eyes and brains are actually capable
of experiencing only a small fraction of the visual stimulus that constantly
bombards us. You’d probably assume that our eyes encode the visual scene we
experience in much the same way as a camera processes an image; light goes in, gets
moved around a bit, then sent to the brain/film/memory card. But no, not the
human eye.
When it comes to fine detail, the sort of useful, accurate,
specific processing is limited to an alarmingly small area. It’s the fovea, the part of the
eye that’s most densely packed with photoreceptors
(only cones, no rods, by the way). It can pick
up on the small details, the finer points, and no other part of the eye can. It’s
like a very small searchlight casting about through the fog of our visual sensory
input. What we essentially do is use the fovea to focus (no pun intended) on
things which our visual systems classify as worthy of attention. Visual
psychology experiments have used tracking
software to follow a person’s eye movements when looking at stimuli such as
elaborate paintings. It’s interesting, the tracking pattern is like someone
tried drawing the painting themselves on an etch-a-sketch while suffering serious
drunken tremors.
But it’s enough. The brain can take this scattering of
detailed glimpses and
build up a detailed and, more relevantly, useful perception of the world itself.
All from a part of the retina that’s no even a millimetre in diameter. Even for
something as small in area as the retina, that’s a pretty pathetic amount of
space given over to detailed perception, don’t you think? Especially when the periphery
of the retina can’t
even encode colour (our brain just infers it later in the processing stage,
if you’re wondering).
But if you did think the fovea was a measly allocation of
useful processing space, look at it this way; this measly bit of retinal space
is sufficient to provide us with the sort of rich detailed vision we take for
granted, despite the fact that it’s mostly the result of brain processing
rather than direct sensation. You want more? Well, if the fovea were twice the
diameter it is, we’d actually need brains the size of beach balls to handle the
data input. And that wouldn’t be practical. We’d need crackers to have paper
hats that were a lot bigger (there may also be other consequences, like needing
bigger wigs if you’re a bald man).
So yeah, the effort that goes into making Christmas happen
is just like our visual perception; far more is going on than we can actually
perceive. But what we have, that is usually more than enough.
See, I can do schmaltzy too, just so you know.
Twitter: @garwboy
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