Re: Somesthesia and Suggestion

From: no email ((no)
Date: Fri Feb 24 1995 - 15:37:57 GMT

> From: "Robert Droy" <>
> To: "yr 3 undergraduates" <>
> Subject: Somesthesia and Suggestion
> Date: Fri, 24 Feb 1995 15:25:22 GMT
> I feel this is not really relevant but this phenomenon of not thinking
> one is feeling something when they are seems to have parallels with my
> own experience.

Hi Robert, not only is your comment relevant, but it anticipates issues
that will be coming up in later Modules, about unconscious perception,
blindsight, and other puzzles of consciousness.

> The doctors tell me my disability means that I shouldn't feel anything
> as I supposedly have no nerve endings. However, as I type this message,
> I believe I can feel the keys. Doctors believe that I only think I feel
> the keys because I can hear the sound of the keys being depressed.

The only way to check for sure is in a controlled test where all
feedback (such as auditory feedback) is eliminated. This is virtually
impossible to do in the case of a motor movement that gets feedback from
the surface involved (the key will only depress so far, and no
further). Since you are obviously able to send a motor command to your
fingers, the feedback in this case could come from the kinaesthetic
(motion sense) signal that the action has been successfully terminated
(by depressing the key as far as it will go). This feedback signal can
then be reorganised by the brain to do the same job that the
somesthetic (touch) signal would have performed, if your nerve endings
for touch had been intact.

So, although only a neurologist could say for sure, my guess is that
kinaesthesia has taken up the function of somesthesia when you are
typing, so that you DO feel the keys, but you feel them kinaesthetically
rather than somesthetically.

The brain is remarkable for its capacity to substitute functions where
necessary. In many cases the result is almost as effective as the intact
function, and it's hard even to detect that anything is different.

> If you follow this argument, does this mean I am imagining the feelings
> that I believe I am experiencing. When I walk, I do tread heavily on
> the floor, in order to gain auditory feedback. I seem to have developed
> a number of strategies like that over the years, but they seem to
> develop automatically without me actually thinking through the benefits
> of each strategy.

Probably the heavy tread plays a double role. It does, as you suggest,
create a sound, which is one form of feedback about what is going on. It
may also enhance the kinaesthetic feedback on the start and completion
of the movement. The brain then integrates this into the experience of
walking, and (although there is no way to know for sure) the experience
is probably the same for everyone, even though the components of which
it is made may differ.

Blindsight has some analogies with this too: There are some brain
injuries that make people "blind," in the sense that they feel they
cannot see (although their eyes are fine). If you show them something,
they say they can't see it. But if you ask them to point to it, they
can (of course you have to coax them to point, because they insist they
cannot see). Sometimes they can also say which way the object is
tilted, and even something about its shape and color -- all without
"seeing"; now that capacity must have been based on SOME sort of
sensation, because they are not in a trance when they answer.

What is their sensation "like," then? They deny that it is visual (and
I think we can take their word for it, because they have had visual
experiences before their injury, and usually still have intact parts of
their visual field too), but then it might take another form.

One candidate, at least for the ability to point in the direction of
the object they are "seeing," is again a kind of kinaesthesia: An
intact part of their brain is the orientation system, which usually
locates things unconsciously so you can turn toward them and THEN see
them. They may be judging the location of the object from the sensation
of an urge to turn toward it.

Of course, this explanation does not explain their (partial) ability to
"see" shape or color, but perhaps there too there are other forms of
sensations that are acting as cues. And who knows, maybe eventually, if
these capacities play a role in their daily lives, they will find it
more convenient to refer to the kind of visual capacity they exhibit as
"seeing" rather than something else -- and, phenomenologically, that
might even be the best description.

> To link this back to hypnosis, if I can unknowingly fool myself that I
> experience these 'feelings' when I don't, does this mean I am a highly
> suggestible individual.

You are only a highly suggestible individual if hypnotisability tests
show you belong in that 15-30% of the population. Otherwise it is more
likely that you are calling a spade a spade: When you feel it, you feel

> Any comments welcome
> p.s. How do I know what I call 'feelings' is what most people call
> 'feelings'? But that's more philosophy than psychology.

There IS a philosophical literature on this question, and the "inverted
spectrum" problem summarises it: How could anyone possibly know that I
am not seeing the spectrum in reverse: Where you see red, I see green,
and where you see green, I see red. Yet we both call exactly the same
things green and red. (1) Who is right? Which is the "real" red
sensation (and why?). (2) How could anyone ever know if any of this was
actually happening? Is it (as Dan Dennett, whom we will encounter later
in the course) would say, a difference that does not make a difference?

Chrs, Stevan

This archive was generated by hypermail 2b30 : Tue Feb 13 2001 - 16:23:15 GMT