If you say “alligator” as a result of seeing the word “alligator,” this is also an example of formal control because there is point-to-point correspondence between the stimulus and the 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