Fast mapping is one way children learn what a particular word means. When they hear a word for the first time, kids can often figure out what it means. This instinctive method of learning uses information the child already knows to help him or her place the word in the right context. Often, the kids narrow down the meaning by excluding possibilities that already have words attached to them and apply the unknown word to the object or action that does not already have a name.
First described in 1978 by Carey and Bartlett, fast mapping is usually applied to children. Kids do not learn their mother tongue through active teaching but rather through picking up words and their meanings through everyday life. For instance, the concept of a black cat is understood by children who identify the word cat as a particular sort of animal and also as a particular inanimate representation of that animal in a book or as a toy. The concept of black enters their minds as a color that can apply to many objects because they hear it used in this context.
All words are new to kids at some point in their lives, and at age two, they know three times as many words as they do at one. If the English language, for example, can be imagined as an entire dictionary, young kids only know some of the words, with large, empty holes where all the potential words could be. As they get older, more of these black holes are filled in. One of the ways this occurs is through fast mapping.
Integral to the concept of fast mapping is that kids use their acquired knowledge to narrow down the range of things a new word could refer to. A little girl who already knows what a black cat is, for example, is at an advantage when presented with a black cat and a white cat. If her mother asks her to point to the white cat and not the black cat, the little girl can exclude the black cat from the list of possible things her mother is referring to.
Even though the room may be full of new objects, the girl can also exclude these from the list of possibilities as she knows what a cat is. Using fast mapping, therefore, the girl can identify the white cat as the object of interest. Thereafter, she also has an idea what white means. Conversely, if the girl knew what white and black meant, but not what a cat was, she could infer from the mother's instruction to point at an object, and the fact that two creatures were white and black, to figure out what a cat was.
Dogs may also be able to use fast mapping. A 2004 study of an intelligent collie showed that the dog could bring back a new item to the researcher that he had not seen before simply by excluding all the other items that had names that he knew. Fast mapping is a very quick process and only requires a few seconds. Adults can also fast map when confronted with one new item among known items.