

Scientists Settle centuries-old debate on perception - dhernandez5622
http://www.physorg.com/news/2011-04-scientists-centuries-old-debate-perception.html

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mbateman
Here's the classic reference to the problem in Locke (which vindicates Locke's
speculative answer here):

[http://books.google.com/books?id=vjYIAAAAQAAJ&dq=essay%2...](http://books.google.com/books?id=vjYIAAAAQAAJ&dq=essay%20on%20human%20understanding&pg=PA83#v=onepage&q=molineux&f=false)

> To which purpose I shall here insert a problem of that very ingenious and
> studious promoter of real knowledge, the learned and worthy Mr. Molineux,
> which he was pleased to send me in a letter some months since; and it is
> this: "Suppose a man born blind, and now adult, and taught by his touch to
> distinguish between a cube and a sphere of the same metal, and nighly of the
> same bigness, so as to tell, when he felt one and the other, which is the
> cube which the sphere. Suppose then the cube and sphere placed on a table,
> and the blind man made to see; quaere, Whether by his sight, before he
> touched them, he could now distinguish, and tell, which is the globe, which
> the cube?" To which the acute and judicious proposer answers: "Not. For
> though he has obtained the experience of, how a globe, how a cube, affects
> his touch; yet he has not yet attained the experience, that what affects his
> touch so or so, must affect his sight so or so; or that a protuberant angle
> in the cube, that pressed his hand unequally, shall appear to his eye as it
> does in the cube." I agree with this thinking gentleman, whom I am proud to
> call my friend, in his answer to this his problem; and am of opinion, that
> the blind man, at first sight, would not be able, with certainty, to say,
> which was the globe, which the cube, whilst he only saw them; though he
> could, unerringly, name them by his touch, and certainly distinguish them by
> the difference of their figures felt.

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strayer
The physorg article mixes up, at first, the nature/nurture question and the
cross-modality of perception question (whether internal representations good
for tactile perception are also good for visual perception). Those are very
different fundamental questions.

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aycangulez
These results were expected by neuroscientists. Different senses are encoded
differently in the brain. So, the subjects were unable to link them at first.
The surprising thing here is the speed the association between tactile and
visual encodings happened, and the article makes that clear.

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perlgeek
Did I miss the link to the original puplication, or did they actually fail to
include it?

[http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.27...](http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.2795.html)

I find a study with 5 subjects a bit sparse, but I guess they are quite hard
to come by...

~~~
jerf
Why would you need more than 5? This isn't a drug trial trying to pick up some
subtle difference in results between taking a drug and not taking a drug. Is
it really plausible that a theoretical person born blind and sighted later in
fact can distinguish between the two but we just happened to get unlucky to
find the five dunces in the world who can't?

Based on what we already know about how the brain works (aka "the prior
probabilities") the chances of such an outcome are pretty much insignificant,
far lower than a naive sample-based argument that ignores what we already know
would show.

~~~
perlgeek
> Why would you need more than 5?

because humans are quite diverse

> Is it really plausible that a theoretical person born blind and sighted
> later in fact can distinguish between the two but we just happened to get
> unlucky to find the five dunces in the world who can't?

We don't know which percentage of blind people can distinguish objects by
sight once they start to see. We don't know if it's all-or-nothing or not.

If half of blinds can, there's still a 3% chance to get the published results
from five subjects. If it's 30%, the chances grow to 17%.

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dhs
I find this very interesting. If I understand this correctly, the suggestions
are: (1) the "slate" is relatively "blank" to start with (abstract objects,
for instance, do not "exist", in the sense that they are inheritable); (2) a
generic _ability_ to abstract could very well be inheritable; (3) the "slate"
remains in a "writeable" state longer than previously expected - the right
"nurture" can enable the unfolding of potential abilities even relatively late
in life (abstract objects can _become_ "real", even though they don't "exist",
in the sense that they can become "meaningful").

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nitrogen
It sounds like they didn't actually test Molyneux's question at all, or prove
anything about perception. It sounds more like an additional data point to
nudge our understanding of the brain toward greater plasticity.

~~~
JacobAldridge
Molyneux's question: Could a man, blind since birth who can tell the
difference in shapes only by feel, given suddenly the ability to see be able
to distinguish by sight those shapes?

Pawan Sinha's test: They took five people who had been blind since birth,
performed the surgery to restore the sight, and performed the test which
indicated that they could connect the tactile experience with a visual one no
better than chance.

It's a very small sample size, to be sure, but to claim "they didn't actually
test Molyneux's question at all"? Not sure which part of the article you
missed.

~~~
nitrogen
The article says the subjects were given similarly-shaped objects, not a
sphere and a cube (as noted by comments on the article). This gives the
impression that the question whether very rough differences in shape, e.g.
sphere vs. cube, can be distinguished immediately after sight is restored is
still unanswered.

~~~
bobds
I was going to say the same thing. I'd really like to see what objects exactly
they used.

I have a variation on the original question. Suppose someone blind has never
touched a cube. However, he knows that a cube is an object with 6 sides of
equal dimensions and 8 corners. Then his blindness is suddenly cured. If he
sees a cube would he be able to associate it with the description of a cube
that's already in his head?

~~~
perlgeek
> I was going to say the same thing. I'd really like to see what objects
> exactly they used.

They used 20 sets of shape pairs, some examples of which can be seen in the
original publication:

[http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.27...](http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.2795.html)

