Interest is focused on the relationship between how old a person is when he or she first begins to learn a language and the fluency with which he or she can produce and understand that language in adulthood. The goal is to describe and measure the relationship between early experience and environment in language learning. In particular, the attempt is to better understand how sign language is learned in childhood and adulthood for both research and educational purposes. The discussion includes means and methods for distinguishing among special patterns of language learning: signed or spoken, first or second, typical, delayed, or disordered. Experiments designed to examine the relationship between the age at which people first learn to sign and their ability to repeat sentences in American Sign Language (ASL) were carried out. The results demonstrate that signers' ability to repeat ASL sentences depends, in part, upon the length of time they have used sign language and thus helps explain the great variation in production and comprehension skills among adult signers. (Author/JK)