Is explained in
Pavlov's fourth and fifth lectures. In internal inhibition, the positive conditioned stimulus itself becomes, under definite conditions, negative or inhibitory.
Pavlov described two types of internal inhibition.
- Experimental Extinction (or just "extinction") is a simple form, described in Lecture IV, and
- Conditioned Inhibition (i.e., Differential Inhibition) a more complex form, described in Lecture V.