In Verbal Behavior, Skinner notes that “Two facts emerge from our survey of the basic functional relations in verbal behavior: (1) the strength of a single response may be, and usually is, a function of more than one variable, and (2) a single variable usually affects more than one response” (p. 227). These two facts help account for the rich variety of verbal behavior and are also very important facts in the analysis of more complex forms of verbal behavior, especially those related to literature and humor.
He is talking about convergent and divergent relations here