Definitely true.
Dogs are also like people, think of the midwit meme. A few are brilliant, most average, and a few dumb ones.
Growing up my father trained cattle dogs. Out of a group of pups they wouldn't all be good for working dogs, only a small percentage, the rest got sold out given away to be pets or yard dogs. Same with any breed. A few brilliant ones, and then the rest.
Mosha is certainly very smart for a pug. I knew that when I got her though, from the way she responded and paid attention to me when I first met her.
