Hey, all.

A couple of weeks back, I posted a question - it was really a question
for He Who Shall Not Be Named, and of course the question got buried in
another fracas of the type which seems to follow him like a cloud of
flies.

Neil Brooks did address my question, but unfortunately, the vocabulary
he used was considerably above my level. ;-)

My question is really fairly basic, and it concerns the applicability
of conducting visual studies on animals and extending the results of
those studies to humans.

Below is my initial query. The more I think about it, the more it bugs
me, and I'd really like to understand what the general concensus is.
And please - if anyone chooses to respond, please remember that I am a
lay person - so please use small words. ;))

Thanks!!  (original post below)

BD

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In the absence of strong
supporting evidence, parallels between primates and humans are
EXTREMELY dangerous to draw in a medical context.

I have no CV in anything remotely medical, but
look at the behavior differences: I think it's fair to say that
primates have a lot more 'variation' in how they focus their eyes on
objects through the course of the day. Humans will spend hours and
hours looking at exactly the same thing (be it a book, a computer
screen, a TV)... Animals in the 'wild' are very likely NOT letting
their accomodation sit at a specific distance for hours on end. I
strongly suspect that animals who do not have persistent stimuli at a
static focal length will not maintain focus at any specific focal
length for much more than a few seconds.

We're all told that in our workplaces we should 'relax our eyes' once
and awhile, and take them off the screen for a few moments several
times a day. Do we need to ensure that the baboon down in the zoo takes

a break from studying his banana so that he doesn't get a headache?
Obviously not. Because he varies his focal length all the time -
looking from trees, to the bee buzzing around his lunch, to the bug he
just picked off of his wife's head, and at then to those dorky humans
who walk by staring at him all flippin' day.

Could this mean that the muscles around the primate lens cause the lens

to change shape more often than do humans? Sounds reasonable. Could
more frequent accomodation changes be a variable that will affect the
results of vision studies? I certainly expect so.

Regardless, before results of primate studies are deemed relevant, the
behavioural differences between the species (and there ARE differences)

should be quantified, measured, and eliminated from the list of
variables. For example - if we could teach monkeys to read, to watch TV

or enjoy movies, and thereby expose them to the same stimuli and
accomodation patterns as humans to, THEN we might be able to look at
primate studies and begin to draw analogies.

But given that we are dealing with different species, and that there
are easily quantifiable behavioral distinctions between these species,
I believe that the onus is on those who posit a relevance of the
information to establish that relevance before it is accepted.

If not, why can't we do studies on sloths, or penguins, or goats, and
extend the results to humans? Do not all mammals have similar
structures in their eyes? What about pigs? Pigs are often compared to
humans as being very 'biologically similar' - does this apply to eyes?
Can we start to run studies on pigs and infer relevance of the results
to humans?