There are a lot of members of the animal world who effectively communicate by displaying colors or markings. Squids behave like the deep sea equivalent of a mood ring by turning colors to reflect their mood. While in the human world we can't turn a brilliant shade of puce to express ourselves, a vigorous game of "I'll show you mine if you show me yours" usually gets the message across.
People at a poker table can communicate subtle messages just by displaying cards, or in many other cases, failing to show them. After winning a hand many players choose to muck their hand (for those who are new to the game, this is the act of not showing what your cards were after everyone else has folded).
A good way to use the muck to send your opponents false messages is to play some conservative poker and show your hand after every winning hand. By displaying a hand that is worthy of the win you will craft a table image that says you are a cautious player. When that reputation is firmly in place and people simply start folding when you bet, start mucking your hand. This change in your demeanor will get their inner conspiracy theorist going and they will begin to think you're trying to hide a bluff. Even if you are holding four aces, your opponent's inability to see what's in your hand will confuse them.
This seed of doubt will make them think you may be loosening up your play and get them to challenge you more when you are betting.
Good Luck!


