When we were at K9 Kompany today enjoying the K9 Kup - our mini Melbourne Cup - I noticed that the dogs were excited and more active than usual. I thought Penny was trying very hard and watching me more closely than usual - and it seemed to me she was working for the reward of my laughter as much as the treats that she gets intermittently.
I feel sure dogs know what human laughter is.
I remember enjoying a cup of tea in a friend's house and taking no notice of the family labrador, who was lying under the table. He suddenly leaped up and barked to announce the arrival of a latecomer, and we all burst out laughing because we thought he'd been lazy about not announcing the other six people who had already arrived.
I might be guilty of anthropomorphism, but I would say that dog was humiliated by the laughter. He slunk away with his tail between his legs. (He cheered up pretty quickly.)
But the laughter today was different. It was silly laughter, fun laughter. Cindy, our teacher, was wearing a 'beautiful' hat, as one must if attending the Melbourne Cup, and we were enjoying the over-the-top competitiveness of it all. The dogs were leaping around and racing full pelt over and through the obstacles.
Science News, in 2001, published a item about the sounds dogs make when they are having fun - if you listen to the audio clip, it does sound different from normal panting. I'd love to think Penny was laughing too, as we raced around.