Observing the quarrels of others always gives a certain pleasure. After all, why would we follow television programs where people are insulted even when they don't get into a fight? And, apparently, this habit is not only human: for a long time ethologists have known that many animals like to watch duels between males. The activity, according to an opinion shared so far by scholars, would have an effect very similar to the one sadly known in the stadiums: it incites the "spectators" to take the field to give themselves to them. Now, however, a study conducted on a species of shrimp (the orconectes rusticus) shows something very different: faced with fights between dominant males, the spectator crayfish have enjoyed the show, but, placed in the middle of the ring, they lost all interest in the fight (and were invariably defeated). The reason is not yet clear, the researchers explain, but it seems that it also depends a bit on the energy spent in "participation" in the show which then makes the animal listless in the struggle. [AP]