Processes in Classical Conditioning

[darklight]

Quick question:

Toby has a German shepherd that always wags his tail when Toby walks in the door and pats him. Toby decides to get an automatic garage door put in so he can park his car inside the garage overnight. The door opens automatically when the car is within 100 metres. After a week of using the new garage door, Toby’s wife notices that their dog starts wagging his tail when he hears the garage door opening.
Toby goes away to a conference on the weekend and lets his brother come over on Saturday to use the garage to do some work. Toby’s dog eventually stops wagging his tail to the sound of the garage door. Explain why this is so.

The answer says extinction; could this also be because of stimulus discrimination because the dog will only respond to Toby and not Tony's brother even though they are "similar".

[zvezda]

Quick question:

Toby has a German shepherd that always wags his tail when Toby walks in the door and pats him. Toby decides to get an automatic garage door put in so he can park his car inside the garage overnight. The door opens automatically when the car is within 100 metres. After a week of using the new garage door, Toby’s wife notices that their dog starts wagging his tail when he hears the garage door opening.
Toby goes away to a conference on the weekend and lets his brother come over on Saturday to use the garage to do some work. Toby’s dog eventually stops wagging his tail to the sound of the garage door. Explain why this is so.

The answer says extinction; could this also be because of stimulus discrimination because the dog will only respond to Toby and not Tony's brother even though they are "similar".

I think extinction is more correct. It doesnt mention anywhere that the dog wags its tail when Toby is near. And the stem says that the dog "eventually stops wagging  his tail to the sound of the garage door", implying that whoever is there, the dog doesnt wag its tail.