What the instructor said is a bunch of crapola. I had a brother/sister team. The female passed at 12 and the boy lived on to 16. They were so close when one was scratching his ear the other was doing the same. He cried for several weeks and looked for her. I have since learned that if you have two ( dog or cat or mixed dog and cat) you take the surviving one with you when you put down the other. They smell the body and know that their friend is gone. It worked well with my yorkie and her cat friend.
You might ask for a refund and find a more intelligent trainer.
__________________  RIP my darling little Gina |