[Matti]

Perceptual Control Theorists would argue that you don't understand behavior if you think that we, or other animals, respond to stimuli.

"The illusion of stimulus and response [..] What we see from outside the system is that the crosswind pushes sideways on the car and the front wheels of the car immediately cock into the wind, preventing any important change in the car's path. It looks just as if the car is being stimulated by the wind, and is responding by turning its front wheels into the wind. Of course we know that neither the car nor the driver can sense the crosswind; this appearance of stimulus and response is an illusion. The true explanation is a little more complicated than the stimulus-response explanation would be, but not much more complicated.

But we can see now how the impression that stimuli cause responses could arise, even if the system in question is really a control system that works as just described."

-- William T. Powers, A Brief Introduction to Perceptual Control Theory: http://www.benchpress.com/aboutPCT.htm