On 29 Mar 2005, Claudia Stanny contributed two challenging points in
response to my argument that brain activity and learning in response
to psychologically-meaningful stimuli indicate consciousness:
>
> So if this is to be taken as evidence that the brain damaged participants (who
> show differential responses based on meaning) have consciousness, does this
> mean that the so-called "normal" participants (who did not show these
> differential responses) do not?
It's curious, all right, but I don't think it invalidates the
argument. Various ad hoc explanations could be advanced to explain
the response of normals. Schiff et al say about this that the "normal
subjects reported that they recognized the time-reversed stimuli as
speech and realized that it was meaningless", and that possibly
"these subjects attempted to form associations and engaged
attentional resources". In any case, it's a problem in explaining
the response of the normals, not the brain-damaged, and fortunately,
we have other criteria for consciousness in the normals. But the
differential response to meaningful and meaningless presentation in
the brain-injured is certainly intriguing if not persuasive.
>
> As I recall, there are studies showing successful operant conditioning of
> decorticate cats. Does this mean that the brain is not required for conscious
> experience (again, if we assume that the capacity to learn an operant response
> is the definition of consciousness)?
I'd like to see those studies. I'd guess they used aversive
conditioning, probably electric shock.But I can see where I'm digging
myself a hole, because I really don't want to ascribe consciousness
to invertebrates (well, maybe the octopus, because they're pretty
smart). I think the operant study could be strengthened if they had
shown that only certain kinds of stimuli known to be cognitively
meaningful to the patient worked--the Beatles, say, as opposed to
Mozart. I doubt that studies of learning in lower organisms would
work with such reinforcers. And actually, what intrigues me the most
about these two studies are the kind of stimuli that their patients
responded to. So I withdraw the claim of any kind of learning, and
require that the learning be in response to cognitively-meaningful
stimuli. In fact, that's what the two studies have in common, as one
of them doesn't even involve learning.
The view described in the abstract appended below also deserves
consideration.
Dev Med Child Neurol. 1999 Jun;41(6):364-74. Consciousness in
congenitally decorticate children: developmental vegetative state as
self-fulfilling prophecy.
Shewmon DA, Holmes GL, Byrne PA.
Pediatric Neurology, UCLA Medical Center, Los Angeles, CA 90095-
1752, USA. [EMAIL PROTECTED]
According to traditional neurophysiological theory, consciousness
requires neocortical functioning, and children born without cerebral
hemispheres necessarily remain indefinitely in a developmental
vegetative state. Four children between 5 and 17 years old are
reported with congenital brain malformations involving total or near-
total absence of cerebral cortex but who, nevertheless, possessed
discriminative awareness: for example, distinguishing familiar from
unfamiliar people and environments, social interaction, functional
vision, orienting, musical preferences, appropriate affective
responses, and associative learning. These abilities may reflect
'vertical' plasticity of brainstem and diencephalic structures. The
relative rarity of manifest consciousness in congenitally decorticate
children could be due largely to an inherent tendency of the label
'developmental vegetative state' to become a self-fulfilling
prophecy.
>
> Although I am a cognitive psychologist (and I am under no circumstances a
> dualist), I am inclined to suggest the advice from Wittgenstein on this one:
> What we cannot speak about we must pass over in silence.
Ah, but we've just been accused of avoiding the issue. On the
contrary, we're only going to get where we can speak about it (that
is, understand it) if we don't pass over it in silence (that is, we
discuss it and do research). Whew! A bit too much metaphor for me
there.
Stephen
___________________________________________________
Stephen L. Black, Ph.D. tel: (819) 822-9600 ext 2470
Department of Psychology fax: (819) 822-9661
Bishop's University e-mail: [EMAIL PROTECTED]
Lennoxville, QC J1M 1Z7
Canada
Dept web page at http://www.ubishops.ca/ccc/div/soc/psy
TIPS discussion list for psychology teachers at
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