While I was growing up, I had a wonderful dog named Cyndi. She would always come running when we called her name in a sweet sing-songy manner. She would also come running if we called her by other names in that same sing-songy manner. It was pretty clear that she wasn't responding to her name, but to the way we were calling her.
Scientists are digging into why this is. In a new article from the New York Times, they discuss findings from dogs' brain responses while getting an MRI.
"As with people’s brains, parts of dogs’ left hemisphere react to meaning and parts of the right hemisphere to intonation — the emotional content of a sound. And, perhaps most interesting to dog owners, only a word of praise said in a positive tone really made the reward system of a dog’s brain light up."
However, dogs ARE listening to the words you say. If you call your dog "stinky" enough times in a sweet manner, he will assume "stinky" is a word of praise.
Read all the findings in the article link below.
New York Times. With Dogs, It's What You Say -- and How You Say It.