Of course, not all public stimuli have collateral private stimuli. A rash may in fact not itch. An area of swollen or bruised skin may not hurt.
A way in which the verbal community brings verbal behavior under the control of private stimuli that has the following features:
A private stimulus
A collateral public stimulus
Reinforcement for a given response contingent upon the presence of the public stimulus
The type of private stimulus
Whether or not there is any causal relationship between the public and private stimulus (they need only be correlated)