Abstract: Word learning plays an important role in language acquisition and influences the development of other cognitive domains. Susan Carey suggested first that it involved a Fast Mapping process in word learning when she was investigating the phenomenon of children’s highly-expanded vocabulary. Many researchers studied the mechanism of Fast Mapping during the last two decades. One kind of researchers suggests that children can use a set of “cognitive biases” to guess the meaning of a new word. The second kind of researchers emphasize that language environmental factors, such as word frequency, utterance final position, influence Fast Mapping process. The newest research trends, such as Emergentist Coalition Model (ECM) and the Bayesian Inference Model of word learning, tend to believe that both cognitive ability and language environment are important for fast mapping; however, these theories are not unanimous as referring to the influencing time and proportion of the two factors

Key words: word learning, fast mapping, Bayesian Inference, self-monitoring