This process of gradual learning is known as a. habituation
Step-by-step explanation:
Habituation is when a person or a being learns to react to something by the virtue of gaining that stimulus again and again, and getting used to reacting to it.
Habituation here is made by the fact that Katrina trains her dog to sit by pointing at him repeatedly by giving verbal commands.
The verbal command is something that the dog already understands so the pointing is what the dog learns by associating it with the same command.
The dog is able to combine the two commands and seem to understand the same thing from either.