Another gesture I've observed in cats is when they'll be either sitting or lying down, occasionally the tail will rise up and simply flop back down, to either the original position or to a different position. If the cat is simply looking around at nothing in particular, I take this to be another sign of contentment. However if the cat is looking intently at me at the same time as the tail flop, I'm almost sure that it is "plotting," perhaps in a playful mood and perhaps planning a bit of mischief.
Tail "flop"
Another gesture I've observed in cats is when they'll be either sitting or lying down, occasionally the tail will rise up and simply flop back down, to either the original position or to a different position. If the cat is simply looking around at nothing in particular, I take this to be another sign of contentment. However if the cat is looking intently at me at the same time as the tail flop, I'm almost sure that it is "plotting," perhaps in a playful mood and perhaps planning a bit of mischief.