STUDIES WERE MADE OF THE ABILITY OF KINDERGARTEN CHILDREN TO CONTROL CORRECT PLURALIZATION RULES FOR ENGLISH NOUNS. PRODUCTION AND RECOGNITION TASKS WERE USED, WITH CARTOON PICTURES OF ANIMALS WITH NONSENSE NAMES. THE CHILDREN WERE ASKED TO GIVE SINGULAR NAMES FROM CORRECT PLURAL NAMES, AND VICE VERSA, AND TO CHOOSE THE BEST NAMES FOR THE ANIMALS. TWO FURTHER SERIES OF STUDIES EXAMINED SPECIAL RULES USED BY THE CHILD AND THE NATURE OF HIS PLURALIZATION AS COMPARED TO THE STANDARD RULES OF ADULT ENGLISH SPEAKERS. THE DIFFERENCE BETWEEN PRODUCTION AND RECOGNITION PROCEDURES WAS FOUND TO BE CHARACTERIZED IN TERMS OF PATTERNS OF ERRORS, RATHER THAN SOLELY IN QUANTITATIVE TERMS. IT WAS ALSO DISCOVERED THAT THE SUBJECT DOES NOT RESPOND ONLY ON THE BASIS OF HIS KNOWLEDGE OF A PARTICULAR SET OF LINGUISTIC RULES, BUT USES A LARGER STORE OF KNOWLEDGE, INCLUDING GRAMMATICAL RULES, LANGUAGE HABITS, AND STATISTICAL FACTS. (KL)