As an Animal Communicator, my practice is based on the knowledge that animals understand humans' words and intonations. It's validating when science validates what I've intuitively known.
Scientists used dogs trained to lie still in a MRI machine so their brains could be studied while responding to human words and the intonation of those words. The study concluded that dogs and humans use the same part of the brain to process speech and speech recognition.
According to Science News, "Dogs process speech much like people do, a new study finds. Meaningful words like “good boy” activate the left side of a dog’s brain regardless of the tone of voice used, while a region on the right side of the brain responds to intonation."
This video from the Family Dog Project explains how dogs respond to human speech and speech recognition.