Standard 52-card deck jokers, often distinguishable with one being more colorful than the other, are added to commercial decks, as some card games require these extra cards. Modern playing cards carry index labels on opposite corners or in all four corners to facilitate identifying the cards when they overlap and so that they appear identical for players on opposite sides. The most popular standard pattern of the French deck is sometimes referred to as "English" or "Anglo-American" pattern. It has been shown that because of the large number of possibilities from shuffling a 52-card deck, it is probable that no two fair card
Zener cards the experimenter picks up a card in a shuffled pack, observes the symbol, and records the answer of the person being tested, who would guess which of the five designs is on the card. The experimenter continues until all the cards in the pack are tested. Poor shuffling methods can make the order of cards in the deck easier to predict and the cards could have been inadvertently or intentionally marked and manipulated. In his experiments, J. B. Rhine first shuffled the cards by hand but later decided to use a machine for shuffling. In his book, "The New Apocrypha",