[accessibleimage] Response 5: Molyneaux's question rephrased

Here, below,  is a final article that definitely bears on the subject,
"Civilization and the Limpet."  This article discusses the very basic nature
of our spatial understanding and how it is closely linked to our sense of
our own bodies... a form of internal and external touch that lies at the
basis of our visual learning too... Again, if you have already read it,
please excuse the repetition.

I am looking forward to others' thoughts.

Sylvie

Civilization and the Limpet

Martin Wells

Article, page 9,  from the book:

Civilization and the Limpet

Martin Wells (1998)

HELIX BOOKS

PERSEUS BOOKS

Reading, Massachusetts 1998

Library of Congress Catalog Card Number: 98-87056

ISBN 0-7382-0017-4


Limpets sit about, doing nothing much, most of the time. When the tide is
up, or the seashore still wet enough to do so without risk of desiccation,
they potter off to browse the thin coating of algae growing on the rocks
around them. And then, after a while, they return to the spot they left,
settle down, and concentrate on digestion. Day after day. Not an exciting
lifestyle, but interesting because limpets turn out to be remarkably adept
at returning to exactly the place they quit several hours before. They have
to be. It is the only place in the vicinity where the individual's shell
exactly fits the contours of the rock. It has grown to do so precisely
because the animal keeps returning to the same home. A snug fit is essential
if it is to avoid drying up between tides.

So, how does the limpet do it?

And why, says the anthropocentric Philistine at my elbow, should anybody
care?

Because.

Page 10

Because even people who only know about people should care about limpets and
their navigational problems. It will give them an insight into the rise of
civilization and why people can create the things-art and literature and all
that-which some people still believe to be the sole and only proper study
for mankind. The essential difference between us and the limpet, and the
reason this is being hacked out on a word processor by a man and not by a
mollusk whose ancestors had millions of years of head start on mine, is
reflected in the way in which a limpet solves its navigational problems.

Pause and consider the limpet. It must return to the place where it started,
a problem common to all animals that center their lives on a home, be it a
cave, a burrow, a nest, or merely a place where the creature feels secure
because it knows the layout of its immediate surroundings. By what means
might an animal arrange to return to a base? One can list the alternatives.

1. Look for landmarks, move from one to another, then reverse the process on
the return journey.

2. The landmarks don't have to be visual. They could be auditory or
chemical. The smell of home could be a satisfactory beacon.

3. Blaze a trail, creating your own landmarks, and return along that.

4. Take a bearing on a landmark, or on a skymark, sun, moon, or a star, hold
that bearing and return on a reciprocal one. Skymarks are more difficult
than landmarks because they move with time, and any long journey must allow
for this.

5. Remember all the distances moved and turns made. Retrace, or do a little
simple geometry. Dead reckoning would work fine for a limpet crawling across
a rock.

Page  11

Animals of one sort or another have been shown to use every one of these
methods. Even celestial navigation is remarkably common, and not only among
the birds and the bees; most animals seem to include some sort of internal
clock. We now recognize, moreover, that birds at least, and very probably a
wide variety of simpler animals, have a built-in magnetic compass, so that
they can move out and back without the need of landmarks. But how does the
limpet do it?

Not by celestial navigation, anyway. Limpets will home by day or night, in
fog, and when covered by swirling water. They will home, moreover, if the
rock that they are sitting on is rotated through 90 or 180 degrees while
they are away from home-energetic students with crowbars can readily move
the environment so that the sun and stars now appear in all the wrong
places. The limpet plods home unperturbed.

Dead reckoning is a nonstarter, too. If getting home were to depend in any
way on remembering turns and distances, simply displacing the limpet should
leave it disoriented, with no means, other than chance, of finding its way
home. But it doesn't. A limpet knocked off its home scar-this can be done
without damage if the animal is taken by surprise when it is relaxed rather
than clamped down-will find its way home at the next tide, provided-and
this, as we shall see, is important-that it is placed somewhere within its
normal browsing range. A limpet caught off base and displaced does not set
off home on a course parallel to the true route as one would expect if it
were navigating by dead reckoning or depending on a built-in compass. Homing
in this animal does not seem to depend on any methodology that a yachtsman
would recognize as navigational.

It could be blazing a trail, leaving a streak of mucus as it slides along on
the outward journey and returning along that.

Page 12

Except that it doesn't. The return path only sometimes follows the outgoing
track.

Maybe it knows the local landmarks, the detailed topography of its little
patch, a square meter or so around its home. Again, one can undertake simple
experiments to throw the unhappy limpet off course: wait until it leaves for
a browse and then whack away at the rock between limpet and home with a coal
chisel, and change the topography. Or, scrub the area clean, in case the
cues are chemical.

Changing the topography does, indeed, puzzle the limpet some. A groove cut
in the rock between the animal and its home scar (the rock gets worn where
the limpet's shell abrades the surface) stops it. The limpet casts about,
moves along the side of the trench and round the end of the obstruction,
carries on home. Its behavior is much the same if the home scar is covered
with plaster of Paris, except that there is now no home to go to and the
dispossessed animal eventually wanders off or settles down by the periphery
of the obstruction. All indications are that the limpet knows exactly where
home ought to be.

All this implies that the clues are chemical rather than physical. It is the
only explanation that we have left. Since we know that the limpet doesn't
always or even very often return along its outgoing path, we must suppose
that the chemical markers that it is recognizing are located around the
home. The plaster of Paris experiment having incidentally eliminated the
home beacon possibility, the most likely explanation is that the limpet is
picking up trails that it laid on a succession of past excursions. There is
plenty of evidence from other snails that would fit in well with such a
hypothesis. Predatory snails detect and track down their snail prey, and
gregarious species congregate by moving along slime trails left by their
conspecifics.

Page  13

Airbreathing pond snails follow their own mucus tracks to return to the
surface when they need to replenish the bubble of air they take with them
when they dive. And so on. Most seem able to detect the direction taken by
the individual that laid the trail. This is not all that surprising, because
it turns out that mucus trails are highly structured, both physically and
chemically. A limpet would have to distinguish its own trails from those of
its neighbors, crisscrossing its own, but even that should present no great
problems since each individual will produce its own protein or
polysaccharide signature.

So, wait until the animal leaves home and scrub the intervening area,
removing the traces of trails. This turns out to be remarkably difficult.
Water won't do. Detergents and strong alkali--the sort of thing you use to
unclog drains-ought to do it, but don't, not with any reliability. Scrubbing
with proteases and materials that should digest and disperse other
components of the mucus seem to work quite often but not always. The
successes could be due to fouling the environment, as traces of the
materials used to remove the trails are just about as difficult to eliminate
as are the trails themselves.

So the case remains unproven. We are near enough certain that the answer
lies in a highly sophisticated and very acute sense of smell-or taste,
because we are dealing with contact rather than something carried by wind or
water-but the clinching experiment has yet to be done.

Not, in the present context, that that matters very much. What matters are
the mechanisms that the limpet doesn't use. There is no sign of navigation
by land or skymarks. And no dead reckoning.

An ant or a bee uses skymarks. They use the sun as a compass and allow for
the passing of time, so that the return course does not have to be a simple
reciprocal of the angle to the sun taken on the way out.

Page 14

Bees can even communicate courses and distances to their sisters, so that
other members of the hive can be recruited to crop a favorable food source.
(Some years ago a friend, a Swiss professor, had to devise an animal
behavior exhibit for an international exhibition at Lausanne. He set up a
swarm of bees in a glass-fronted beehive, so that visitors were able to see
the bees dancing on the comb as they returned from foraging. The angle to
the vertical face of the comb indicates sun compass bearing, the frequency
with which the bee waggles its abdomen gives distance. The code is quite
simple, and the visitors were invited to plot off course and distance on a
map provided. The bees, it turned out, were all going to the same place.
They were robbing a jam factory on the far side of Lake Leman.)

So bees, like birds, can navigate. And insects, in general, seem to be quite
skillful at learning to find their way about by dead reckoning. Even a
cockroach will learn to run a maze, and there is no question of its laying a
chemical trail, because it does just as well in a new maze of the same
configuration.

For cockroaches, read crabs, or rats. But not snails, or worms, or
octopuses.

So what's the difference?

Snails and the walking predatory worms that one finds in the sea (earthworms
are highly specialized for their boring existence and have reduced nervous
systems) would, one would think, be bright enough to cope with a simple
maze--knowing its way about its environment must be useful to any animal.
But they fail, dismally, compared with the arthropods, let alone the
vertebrates.

This is not surprising, you may well point out. Snails and such are not
renowned for intelligence; this sort of thing is probably beyond the
capacity of their tiny minds.

Page 15

Leaving that aside (practically all animals can be shown to learn, and
generally quite rapidly, if you set them an appropriate task), consider the
case of an undoubtedly intelligent and fast learning relative of the snails.
The octopus isn't thick, by anybody's standards. In the laboratory it can be
taught visual discriminations-squares and triangles and that sort of
thing-just about as rapidly as a cat or a dog, in a dozen or so trials. This
is impressive when you reflect that at the start of the experiment, the
octopus hasn't the foggiest idea what is expected of it. What it learns is
that by coming out of its lair and grabbing one sort of shape it gets fed
(usually a fragment of fish), whereas attacking the alternative results in
something mildly unpleasant (a six-to-twelve-volt shock, not strong enough
to persuade the animal to stay home and ignore the experiment, but enough to
make it pause and consider before attacking). Experiments of this sort allow
us to investigate the perceptual world of an octopus. We can discover
whether it generalizes as we would (between different sizes of the same
shape, for example-it does) and whether it classifies the shapes that it
sees as we would (in general, it does, but there are some fascinating
differences, which tell us about the construction of its brain-but this is
another story and leading away from the main point).

The main point is the discriminations that the octopus cannot make. One
would expect an animal that spends much of its life groping for food under
stones or cracks in the rocks to be good at discriminating by touch. And it
is-it is very good at recognizing the taste of things by touch. Those arms
and suckers have a sensitivity that is well beyond that of my tongue (I
know, I've tried; an octopus can distinguish differences in the
concentration of tastes that we can both detect with a far greater precision
than I). But it fails dramatically in any tactile discrimination that would
require perception of the three-dimensional shape of an object.

Page 16

A sphere, for example, is indistinguishable or very nearly indistinguishable
from a cube, so far as an octopus is concerned-a discrimination I find easy.
And an octopus can't learn mazes.

Consider touch learning. What sources of information do we use when we want
to determine the shape of an object by touch? Try it. Pick something up,
with your eyes shut, and try to determine its shape. Contact with the
fingertips is important, but this in itself won't allow you to determine the
shape of the thing you have grasped. You have to take into account the
relative position of the fingers in contact, and/or the successive positions
of your fingers as you feel the object over. Knowing the position of a
finger is not a matter of external stimuli, but of stimuli from within
telling you about the angles of your joints. You know the relative position
of parts of your own body from receptors in the joints. If you didn't have
this proprioceptive sense you'd be scuppered. You could never work out the
shape of an object by touch.

This is precisely the problem faced by the octopus, or, at a lower level, by
the limpet or any other soft-bodied animal. Their trouble is that they lack
joints. A man or a cockroach can define the position of each of its ends,
fingers or feet or antennae, relative to any other bit of itself at any
time. It can tell how many steps it has taken, define the angles it has
turned through when making a course change, or learn the sequence of
movements that it must make to carry out a task. A soft-bodied animal such
as an octopus has arms and suckers that should be perfectly capable of
carrying out all the manipulations that a man can manage with his fingers.
But it is too flexible, bends in too many places, so that the task of
computing where the ends are, one relative to another, although
theoretically possible, is, in practice, far beyond the capacity of any
reasonably sized nervous system.

Page 17

So there is no question of a soft, unjointed animal's learning to carry out
a skilled manipulative task.

The world is thus divided into two parts. On the one hand are the soft
animals: floating and crawling, swimming and burrowing, flexible animals
that economize on skeletal materials, devoting nearly all their substance to
the important business of reproduction. Most sorts of animal, as it turns
out.

And on the other side of the great divide are the creatures with joints:
ungainly animals, stomping about on legs, beings with limbs like robot
limbs, extravagant in materials but capable of certain important sorts of
behavior unthinkable in the more elegant soft-bodied inhabitants of our
planet. A man or an insect can precisely repeat a movement, checking joint
angles as it goes along. So a bee can accurately construct the hexagonal
units of its honeycomb, a spider can make a web, a man weave a net, chip a
flint, or build a motorcar; a rat can learn to run a complex maze, a bee can
navigate and pass the information to the other members of its community;
writing becomes possible. The key is measurement, measuring what one is
doing with one's own body. Limpets move, but because there is no way for
their soft bodies to accurately monitor the movements they have made, they
can never precisely repeat a movement. Our civilization depends upon being
able to do just this, on a simple, qualitative difference in the nature of
the sensory information available for our brains to work on.

Thus we have two qualitatively different sorts of animal, both successful,
but only one capable of manipulating its environment in a manner that has
led to computers and the atom bomb. We think that this, our, sort of animal
is more successful than the others, which are forever cut off from the
possibility of such clever inventions. Yet we are both here in our millions,
and only one of us is bashing the ozone layer.

Reflect on this next time that you meet a limpet.


----- Original Message ----- 
From: "Lisa Yayla" <fnugg@xxxxxxxxx>
To: <accessibleimage@xxxxxxxxxxxxx>; "Art Beyond Sight Theory and Research"
<art_beyond_sight_theory_and_research@xxxxxxxxxx>
Sent: Sunday, September 03, 2006 6:29 AM
Subject: [accessibleimage] Molyneaux's question rephrased


Hi,
Following are some questions I have about touch and sight. Would
appreciate any feedback, thoughts

In the paper "Recovery from Early Blindness" by Richard Gregory he
describes a man, S.B, gaining vision at the age of 51. Shortly after the
operation he draws pictures from what Gregory calls "touch memory" and
is able to understand objects through vision alone and not touching
them, though they are objects he has known from touch when blind (clock
on wall and written letters). This again touch memory. In his pictures
though he does not enter features which he "had not known previously by
touch".

This seems to answer differently than John Locke's answer to Molyneaux

However S.B had difficulty recognizing faces and facial expressions.
This is also the case for Michael May (blind and regained sight) that he
has difficulty with understanding faces and facial expressions. I was
thinking that perhaps the explanation to this is that facial
expressions, body language are something done "on the fly", there is
movement involved and this is something one can not experience with
touch. Transition of expression involves movement.

In lieu of this would it not seem fair to rephrase Molyneaux problem to:

"If a blind person gains sight will that person, soon after gaining
sight, understand an object from sight alone not having experienced it
by touch from before?"

and/or Could this be compared to an archaeologist who uncovers an object
and doesn't know what it is?

The idea being that touch is very important for sight

Is perhaps sight  the "servant" of touch? That sight discovers things
for us to touch? The original object of development is to touch and
verify?  Is sight the ability to "touch" at a distance? That sight
develops from touch? Sight developed to be able to touch farther away
then the lengths of our arms?

Thanks,
Lisa


http://www.richardgregory.org/

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