Andres Valloud <sqrmax at prodigy.net> wrote:
	Descartes said "I think, therefore I am".  Maybe a more illuminating
	thing to say in this context would be "I experience self-consciousness,
	therefore I am".  If we go down that road, then many things seem more
	clear.
	
	Our self-consciousness "processor" runs threads.  Threads tap on shared
	brain resources, they also have a dedicated storage space we may refer
	to as its state.  The running thread can be interrupted by other
	threads.  Any interrupting thread may become the running thread. 
	Threads may call other threads, return, terminate, etc.  Keeping a
	thread stack requires concentration.
	
I suggest that this is not a useful way to think about thinking.
Some years ago I noticed that if the instruments were sufficiently
distinct in timbre or pitch, I could follow more than one musical
part at once, with no _experienced_ switching.  I could always
"attend" to three parts at once, could "attend" to four parts at once
more often than not, and on one occasion only managed to track five
musical parts.  I want to emphasise that there were no experienced*
attention switches.  I know what an attention switch feels like, and
these days when listening to four parts experience them quite often.
I can still manage three parts, though.  At one and the same time, I
am (as far as I can tell) _continuously_ attending to several musical
parts, and there is another aspect of me that notices that I am doing this.
The "attention points" don't feel as if they are in the same place in my
head, although I am confident that this attention-point-location thing is
an illusion.  If I start thinking about anything, my capacity drops,
and my musical attention starts switching.

I don't believe that I am unique.

Another data point.  While I am typing this and thinking about what to
say, I can whistle, hum, or sing, as long as I don't sign the words.
When I try to sing the words, my typing stops.

I suspect, therefore, that the thing which is single-threaded is the
speech centre, and that it is _verbal_ thinking at most which is
single-threaded, NOT consciousness.

The relevance of this to things like Squeak and EToys is that
programming by direct manipulation may have different consequences for
"thought" than programming by typing words in a code pane, and that
the metaphors we give children (about TELLING little men what to do)
may be the source of sequential thinking, not any intrinsic limitation
in the children themselves.