We will tell our Maltese-yorkie-poo to go get the ball, and she will run into another room and locate it and bring it back.
That’s intelligence beyond even six months.
Then the two inherited Chihuahuas from my wife’s family aren’t intelligent enough to let us know they have to use the restroom. So, it depends on the breed.
Our Chihuahua is so smart its frightening. We have to spell everything. She has us trained to do almost everything she wants.