This isn't quite true, unless your definition of "behavior" includes
apparently involuntary things like endocrine responses, heart rate,
etc. -- and eventually to measurable patterns in neuron chemistry
itself. These things can respond to perceptions like smells and colors,
and so can be used to compare internal states between subjects.
The fact that some of the arguments of the anti-behaviorist crowd
are easily debunked (such as Searle's Chinese Room) is not necessarily
a nod in favor of the strict behaviorists (though I certainly lean
in that direction as well).
-- Lee Daniel Crocker <lee@piclab.com> <http://www.piclab.com/lcrocker.html> "All inventions or works of authorship original to me, herein and past, are placed irrevocably in the public domain, and may be used or modified for any purpose, without permission, attribution, or notification."--LDC