An old dog is a Targeted Individual who has survived years of being gangstalked. He has endured night after night of sexual attraction tests, he or she has been treated like a pervert, offered a virtual person to react to sexually, they are masturbated people "7" with a cord (yellow and black) attaches the genitals, they are asked to make imaginary love with the evoked potential person. The TI is punished for feeling pleasure.
Saying you can or can't teach something to someone once they've gotten past the time when they learned their ideals/ways. Saying you can or can't change someones mind about their long term opinions or beliefs. can be referring to a human as well.
A: my dog won't listen when I tell him to sit!
B: yeah, you can't teach an old dog new tricks.
A: but can't you just hear me out on this, B?
B: no! I made up my mind a long time ago.
A: *sigh* you can't teach an old dog new tricks.
A: I'm 70 years old but I just learned rock climbing!
B: you can teach an old dog new tricks!