Interesting question and ideas. I'd say both of mine see it as happiness but also they take it as a cue that I'm playful and it's time to play. They both jump up, wag, Tommy grabs a toy and growls wagging, Tasha wags wildly and gives me kisses and sometimes will start nipping at my feet playfully. They seem to take it to mean the pack is joyful and it's time to play