Concentration (game)
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Variously themed cards are available for children of all age groups.

Concentration, also known as Memory, Pelmanism, Shinkei-suijaku or simply Pairs, is a card game in which all of the cards are laid face down on a surface and two cards are flipped face up over each turn. The object of the game is to turn over pairs of matching cards. Concentration can be played with any number of players or as solitaire, and is an especially good game for young children, though adults may find it challenging and stimulating as well. The scheme is often used in quiz shows and can be employed as an educational game.

Rules

Concentration is traditionally played on the floor, though any table large enough to display all the cards will do. Any deck of playing cards may be used. The rules given here are for a standard deck of 52 cards, which are normally laid face down in 4 rows of 13 cards each. The two jokers may be included for a tableau of 6 rows of 9 cards each.

In turn each player chooses two cards and turns them face up. If they are of the same rank and color (e.g. 6♥ and 6♦, Q♣ and Q♠, or both jokers, if used) then that player wins the pair and plays again. If they are not of the same rank and color, they are turned face down again and play passes to the player on the left. The game ends when the last pair has been picked up. The winner is the person with the most pairs, and more than one person may tie for first place.

Solitaire

Concentration may be played solo either as a leisurely exercise, or with the following scoring method: Play as normal, but keep track of the number of non-matching pairs turned over (this may be done using poker chips, pennies or by making marks on a sheet of paper). The object is to clear the tableau in the fewest number of turns, or to get the lowest possible score.

Strategy

Over the course of the game, it becomes known where certain cards are located, and so upon turning up one card players with good memory will be able to remember where they have already seen its pair.

Young children have a tendency to think they know where pairs are and to turn over the one they are sure of first, then be stumped finding its mate. A better strategy is to turn over a less certain card first, so that if wrong, one knows not to bother turning a more certain card over.

An ideal strategy can be developed if you assume players have perfect memory. For the One Flip variation below, this strategy is fairly simple. Before any turn in the game, there are t cards still in play, and n cards still in play, but of known value. On your turn, you should flip over an unknown card. If this card matches one of the known cards, you should obviously flip up its match. Less obviously, if the card does not match any known card, you should still flip up one of the n known cards. The mathematics follow:

If you randomly flip one of the remaining unknown cards, you have a 1/(t-1-n) chance of getting a match, but you also have a n/(t-1-n) chance of providing your opponent with the information needed to make a match.

There are some exceptions to this rule that apply on the fringe cases, where n = 0 or 1 or towards the end of the game.

Variations

Many of these may be played in combination with one another:

• Any Color: A version especially good for young children where matching pairs need only be of the same rank, not the same color. When playing with jokers, these count double because they are more difficult to match.
• One Flip: Players who make a successful pair win these cards but do not go again until their next turn.
• Zebra: In an interesting twist, pairs may only be formed by cards of the same rank, but opposite in color (so 7♦ would match with 7♣ or 7♠, but not 7♥)
• Two Decks: For a much longer game, shuffle together two 52-card decks and lay them out in 8 rows of 13 cards (9 rows of 12 cards if using jokers). Pairs must be identical (same rank and same suit, as in 10♣ with 10♣).
• Double Decker Checkerboard: For a slightly easier version of the two-pack game, use decks with different backs and shuffle them separately. Deal them out in a checkerboard pattern (red, blue, red, blue, etc.) The different backs help identify the position in the grid and significantly reduce the possibility of which cards will match.
• Fancy: The cards need not be laid out in a strict rectangular grid and many players have their own special layouts that include circular, triangular, or diamond-shaped formations. Dealers may select any layout they wish.
• Spaghetti: Same rules as standard concentration, only the cards are not laid out in neat rows. They are strewn randomly about on the floor. Spaghetti is a good alternative to 52 Pickup.