Dogs don't know about ...

Dogs don't know about beginnings, and they don't speculate on matters that occurred before their time. Dogs also don't know - or at least don't accept - the concept of death. With no concept of beginnings or endings dogs probably don't know that for people having a dog as a life companion provides a streak of light between two eternities of darkness.
 Stanley Coren

Quotes from the same author

Compared to their sense of smell, dogs seem to pay a lot less attention to their sense of taste. Apparently they believe that if something fits into their mouths, then it is food, no matter what it tastes like.
 Stanley Coren