Elsa,
Several people have responded describing the functionalist in sociology and
I don't really have anything to add to that.
Your question, however, brought to mind a discussion that I had with one of
my colleagues recently. We were reading a chapter by Bill Clancey on
situated cognition. Clancey makes reference to the "functional hypothesis"
as discussed by Newell and Simon and also to "functional psychology" as a
school usually associated with Dewey. I raised the question as to whether
or not the two terms were related.
My first position was that the terminological convergence was coincidental,
but I'm not so sure anymore. The argument hinges on what you consider to
be scope of functional psychology. If, (as has been argued by people like
Eric Bredo) you consider functional psychology to be a "once and future
discipline" (to appropriate a phrase from Mike), then there is no
connection between the "functional hypothesis" and "functional psychology".
On the other hand, if you accept the use of "functional psychology" as a
term that can be broadly applied to virtually all research in psychology in
this country since Dewey (the way the term is used in later editions of
Hilgard and Bower's "Theories of Learning"), they are (at least weakly)
related since today's cognitive psychology can be seen as Dewey's
functionalism in yet another incarnation.
---Tim