"An elephant never forgets," well neither do dogs. I opened the door and Elsa went into her "they're here, they're here" routine. It had been a year since she last saw them; but she knew exactly who these visitors were and welcomed them into our home. You see dogs don't forget; they don't forget the good or the bad.
I remember my friend asking me if Luke would remember her after so many years. She met him once, very briefly when he was young and then several years later. Luke was an easy read sort of guy. If you were a real stranger then he treated you as such; if he knew you, it was clearly obvious. When my friend walked into our home, it was obvious that she was a friend and not a new stranger. Elsa is the same, although she really loves humans there is a clear difference between strangers and friends. A dog never forgets.
Along with the good memories there are also the bad things that dogs remember. To this day Elsa hates doves, yes friendly little cooing doves. They gave her a bad startle many times when she was little so now she tries to rid them from her yard. She does not forget. Can dogs get over bad experiences? Yes. But it takes patience and work to make the bad memories into neutral ones. If you do a good job at desensitizing and creating a new and positive association to the past negative one; those can sometimes be overridden.
Desensitizing is the act of creating a neutral or non issue out of something that has in the past, created an emotional response.
Counterconditioning is creating a new and different response to a stimulus.
Dogs learn through association and if that association is a negative one it can be very difficult to undo. I am often given a "tough case" to rehabilitate when the owners haven't a clue what is going on. Looking at the big picture and performing a detailed forensic type investigation I can often figure out where it all began. But, sometimes there is no figuring out where a behavior came from and you must simply direct all your attention to the behavior itself.
Of course like us, dogs are all different. Some remember, react and rehabilitate more readily than others.
Dogs do not forget. Yes, they can be rehabilitated but they will never forget. So the next time you wonder if your dog will remember your friend from a year or two ago, don't; because they will most definitely remember.