This paper presents a theory of the child's acquisition of the phonology of his native language. The theory predicts learning, measured by correct pronunciation of phones, as a function of ease of perception. The general prediction is that the more discriminable phones are learned earlier and the less discriminable ones later. Finally, the theory is compared with some previous suggestions in this field.

This paper discusses various types of phonological phenomena, some of the concepts that linguists have employed in dealing with them, and certain questions to which previous work in phonological theory has not provided satisfactory answers. These considerations lead to the recognition of some distinctions heretofore overlooked and to a new theory of phonology, certain features of which are outlined.

This Issue of Language, dedicated to Y. R. Chao, was planned by Bernard Bloch, who began work on it before his death on 26 November 1965. The duties of acting editor were then assumed by Warren Cowgill, who completed the editing and sent the copy to the printer; special thanks are due to him for his devoted service in a difficult time. Finally, the correction of proofs was supervised by the present editor.