Andres Valloud <sqrmax at prodigy.net>, writing about sequential thinking,
cited:
	a theatrical production an account of a long exchange of messages
	which are answered?  If so, how many simultaneous "processes" would a
	typical theatrical production have?

concentrating on the *verbal* aspects; whereas one can certainly have a
verbal interchange and a non-verbal interchange elsewhere happening at
the same time,

and
	When I was learning how to type I noticed that I'd think what to say,

again, concentrating on a *verbal* task.

I dare say we're all agreed that
 - people can do more than one thing at once
 - people can't do MANY things at once
 - people can only say or type one thing at a time

The question I think is interesting is whether telling students to
think in terms of objects TALKING to each other makes it harder for
them to think of concurrent implementations.  Would some other
metaphor (perhaps sending couriers with messages, or thinking about
a factory with things concurrently moving from machine to machine
at the same time) make it easier for them to think of and understand
concurrency?

All I know about Ken Kahn's ToonTalk is what I've read in this thread,
but it sounds as though uses a "physical" rather than "verbal"
metaphor, so I think his observations are particularly interesting here.