I put it down to the work of the relevant collective force, in this case the one of simple joy and pleasure. As most people don't believe in the existence of the collective forces, I guess one has to put it down to magic or pyschic.
I've come across the collective forces through the particular type of logic that I apply to ancient languages, art etc, in unravelling the symbolism. It seems the ancients certainly understood that the collective emotional forces
existed, separate from themselves yet, as part of the collective, each person is attached to each force.
IMO, the ancient Greeks called them gods and gave names to these collective forces; for example, Aphrodite is the name of the collective force of love; Ares to a collective emotion associated with that required to be felt by those soldiers going into battle.