Well, they love your smile! Researchers from the University of Helsinki say it gives your dog an extra shot of the feel-good hormone oxytocin. And that not only makes your dog happier – it makes them trust you more! And when you and your dog are both pumping out oxytocin, it increases your bond so you feel closer. So, go ahead and smile and laugh with your dog. They can read your happy expression and it makes them happy, too.