In each of the preceding seven elementary relationships, the form of the response is specifically determined by the controlling variable. However, in almost all cases, each of the different types of controlling variables requires an additional factor to be present before the appropriate verbal response is emitted. This factor is a listener. Since the reinforcement for verbal behavior is mediated by a listener, the presence of one is a discriminative stimulus for verbal behavior in general. In other words, the presence of a listener sets the occasion for the speaker to be reinforced for speaking.
A type of controlling variable with the following features:
The audience is usually a listener in the presence of whom verbal behavior is typically reinforced
It controls a group of response forms
Whether or not the listener provides reinforcement for the current response
The size or specific nature of the response forms controlled