Formal control exists whenever a controlling variable evokes a response and there is point-to-point correspondence between the controlling variable and the response. To determine formal control, it is irrelevant whether or not there is formal similarity between the controlling variable and response, exactly what the formal characteristics of either the controlling variable or the response are, or what the dynamic characteristics of either the controlling variable or the response are.
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