Only Sonny of my 3 cats is a super purr boy. And purr he does. He purrs when he's happy. He purrs when he's sleeping. He purrs when he's scared. He purrs when he's hurting. He purrs when I feed him .Purr purr purr. The youngest, Roman, only purrs when he's cuddling with my nephew (his human) and Maxy will purr when he's being pet and gets excited (right before he tries to bite your hand off because he's overstimulated. Usually purring is a sign that he's about to get bitey and to back off.