All of the elementary verbal relationships we have studied thus far—echoic behavior, copying a text, taking dictation, and textual behavior—are examples of formal control; that is, they are functional relationships in which there is point-to-point correspondence between the controlling stimulus and the evoked response.
When a controlling variable evokes a response and has the following features:
There is point-to-point correspondence between the controlling variable and the response
Whether or not there is formal similarity between the controlling variable and the response
Formal characteristics of either the controlling variable or the response
Dynamic characteristics of either the controlling variable or the response