A flexible and effective mnemonic for memorizing long lists of items in a specific numerical sequence by forming mental associations with a list of words that are already known or can be generated to order. A popular set of peg-words, easy to remember because they rhyme with the names of the first ten natural numbers, is: one is a bun, two is a shoe, three is a tree, four is a door, five is a hive, six is sticks, seven is heaven, eight is a gate, nine is wine, ten is a hen. To memorize the ten commandments, one might form vivid mental images such as these: (1) a bun inscribed with One God in icing; (2) a shoe decorated with graven images of gods, animals, and fishes; (3) a tree into which children have climbed and are loudly taking God's name in vain; (4) a door hung with a calendar showing the Sabbath days blacked out; (5) a hive being presented to honour one's father and mother; (6) sticks being used to kill someone; (7) heaven up above, with a sign No Adultery written in the clouds; (8) a gate with a thief climbing over it to steal something; (9) a wine bottle sticking out of the pocket of a witness giving false testimony in court; (10) a hen being coveted by a neighbour over a garden fence. When the time comes to recall them, bun should bring back the image of the inscription One God, shoe should remind one of the graven images decorating it, and so on. For lists of unlimited length, the standard system used by experts is to generate peg-words from numbers by using a technique introduced in 1634 by the French mathematician Pierre Hérigone (1580–1643) in which each of the ten digits has one or more consonants assigned to it, and then words lending themselves to vivid images are formed from numbers by inserting vowels freely. In the modern version of the Hérigone code, 1 is associated with t or d; 2 with n; 3 with m; 4 with r; 5 with l; 6 with ch, j, or sh; 7 with k, hard c, or hard g; 8 with f or v; 9 with p or b; and 0 with s or z. The peg-word for the number 1 might be toe, 31 might be mat, and 131 might be tomato, and so on. The system is also useful for memorizing numbers, such as 1879, the year in which the world's first psychological laboratory was opened in Leipzig, which might be translated into a mental image of a dove cup—a trophy cup engraved with an image of the dove of peace to commemorate the event; but one's own images always work best, especially if they are more bizarre than that. Also called keyword mnemonic. See also mnemonist.