Concentration, also known as Memory, Pelmanism, Shinkei-suijaku, Pexeso or simply Pairs, is a card game

Card game

A card game is any game using playing cards as the primary device with which the game is played, be they traditional or game-specific. Countless card games exist, including families of related games...

 in which all of the cards

Playing card

A playing card is a piece of specially prepared heavy paper, thin cardboard, plastic-coated paper, cotton-paper blend, or thin plastic, marked with distinguishing motifs and used as one of a set for playing card games...

 are laid face down on a surface and two cards are flipped face up over each turn. The object of the game

Game

A game is structured playing, usually undertaken for enjoyment and sometimes used as an educational tool. Games are distinct from work, which is usually carried out for remuneration, and from art, which is more often an expression of aesthetic or ideological elements...

 is to turn over pairs of matching cards. Concentration can be played with any number of players or as solitaire

Solitaire

Solitaire is any tabletop game which one can play by oneself or with other people. The solitaire card game Klondike is often known as simply 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 show

Quiz Show

Quiz Show is a 1994 American historical drama film produced and directed by Robert Redford. Adapted by Paul Attanasio from Richard Goodwin's memoir Remembering America, the film is based upon the Twenty One quiz show scandal of the 1950s...

s and can be employed as an educational game

Educational game

Educational games are games that have been designed to teach people about a certain subject, expand concepts, reinforce development, understand an historical event or culture, or assist them in learning a skill as they play...

.

Rules

Any deck of playing cards may be used, although there are special cards available, as shown in the picture above. 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 joker

Joker (playing card)

Joker is a special type of playing card found in most modern decks, or else a type of tile in some Mahjong game sets.-Name:It is believed that the term "Joker" comes from a mispronunciation of Jucker, the German/Alsatian name for the game Euchre. The card was originally introduced in about 1860 for...

s 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 of hearts and 6 of diamonds, queen of clubs and queen of spades, or both joker

Joker (playing card)

Joker is a special type of playing card found in most modern decks, or else a type of tile in some Mahjong game sets.-Name:It is believed that the term "Joker" comes from a mispronunciation of Jucker, the German/Alsatian name for the game Euchre. The card was originally introduced in about 1860 for...

s, 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 there may be a 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

Penny

A penny is a coin or a type of currency used in several English-speaking countries. It is often the smallest denomination within a currency system.-Etymology:...

 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.

It is common for many players 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 we assume that 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. The current player should flip over an unknown card. If this card matches one of the known cards, the match is next chosen. Less obviously, if the card does not match any known card, one of the n known cards should still be chosen to minimize the information provided to other players. The mathematics follow:

If a remaining unknown card is chosen randomly, there is a 1/(t-1-n) chance of getting a match, but also a n/(t-1-n) chance of providing opponents 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: Pairs may only be formed by cards of the same rank, but opposite in color (so 7 of diamonds would match with a 7 of clubs or spades, but not a 7 of hearts)
• 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, so the 10 of clubs would have to match the other 10 of clubs).
• Two Decks Duel: Duel is a two-player game where the playing field is divided into two separate parts. Each player shuffle a full 52-card deck and lay it out in 4 rows of 13 cards. The players cannot access each others' cards. Player one starts, flipping one card face-up, then player two selects one card from his/her own side. If the pair is a match, cards are removed, if not, they are flipped back. Pairs must be identical (same rank and same suit, so the 10 of clubs would have to match the other 10 of clubs). After every turn roles are exchanged, in this case: player two flips a card and player one answers.
• 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
  Checkerboard
  A checkerboard or chequerboard is a board of chequered pattern on which English draughts is played. It is an 8×8 board and the 64 squares are of alternating dark and light color, often red and black....
  
   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
  52 Pickup
  52 Pickup or 52-Card Pickup is a children's game, using a standard deck of 52 playing cards, that verges on a practical joke. The name has also been used for solitaire versions and for legitimate educational children's games that are based on the fundamental principle of picking up scattered cards...
  
  .

Concentration is not limited to playing cards. Many versions of the game that are designed for children may have different themes. In some computer versions, the cards may randomly move to increase the difficulty.

External links

• Pexeso - Free online Flash based Concentration Game
• Concentration - the Memory Games - The only concentration game that implements Two Decks Duel.
• MemRoyal - a computer program of the game (requires Java).
• Memory Game - Flash based Concentration Game
• Memory Game - Concentration Game
• Play Memory Test Game Online - at Funmin
• Pairs - an open source
  Open source
  The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
  
   concentration game written in Seed7
• Variation of memory game - Online. You search for variable number of 'pairs'. 2 - 4 'pairs'.
• Classic Memory Game - Play online or download.
• Mandala Memory - a concentration game for the iPhone.
• Photo Pairs - An online HTML5 concentration game with photos from Flickr
  Flickr
  Flickr is an image hosting and video hosting website, web services suite, and online community that was created by Ludicorp in 2004 and acquired by Yahoo! in 2005. In addition to being a popular website for users to share and embed personal photographs, the service is widely used by bloggers to...