I have been told and have even read that when a cat holds her tail in a vertical position and the end of the tail vibrates it means that the cat is very happy. This has intrigued me because in the 5 years my Cucumella has lived with me she has never done this and yet I have the impression that she is very contented and happy. I have never known her to have any aggressive gesture towards anybody, she is very sociable even with visitors she has never seen before. She walks around almost permanently with her tail right up with end of it curling towards her back but there is no vibration at all.Could this be a wrong interpretation?