It’s sad but true. I have a Jack Russel Terrier and two larger mutts. One is about 45 lbs, the other about 65lbs.) The JRT loves to lay on human chests (I think the heartbeat soothes him in some way). The other two get jealous and want to do the same, crushing the wind out of me.
Big dogs never seem to realize that they’re bigger than they were when they were puppies-- they think they can still do the same things they did then. One of my puppies used to run and hide beneath the couch when she was in trouble. One day she simply didn’t fit any more. She cracked her head and yelped in puzzlement, and began sniffing the couch as if to make sure I hadn’t switched them. (Humans do that.)
My grandma’s 110 lb. Airedale used to try to sit on my lap. Considering I’m only about five pounds heavier than that myself, hilarity ensued. He remembered being able to do that when he was a pup, and occasionally he would give me an accusing look as if to say, “You shrank your lap! Now where am I supposed to sit?”
The only big dog I ever knew to realize his size was a Great Dane that belonged to my mother. His name was Zeus, and Christ was he massive. His head was larger than my torso. However, he was as gentle as a butterfly, especially around children. I will never forget, as long as I live, seeing him play with one of the neighborhood kittens. The kitten was not much bigger than Zeus’s paw, yet it had him “pinned” to the ground, yanking at his collar. Zeus rolled around, always careful not to step on or lie on the kitten and they had a fine time. (Wish like hell I’d gotten pictures.)
When my medium-sized dog and the little dog wrestle, the bigger one lays down on the ground so the little guy can reach. From what I’ve observed, they seem to have an intricate etiquette of “what’s fair” in their wrestling, and if one takes advantage of the size difference too blatantly, the other will quit. I guess it’s less fun if there aren’t handicaps to keep things even.