When people came to realize that there are ways to learn language without using the vocal apparatus that other animals don't have, our notions of unique human capabilities were in for a shake-up. Amon reports here on pioneering chimpanzees' achievements with the three basic systems which have been designed or adapted for their instruction. Young readers will meet Washoe, who learned to combine signs in Ameslan (already used by the deaf) to make new sentences, and her successors, one of whom called an uncooperative experimenter ""dirty Roger,"" and another who translates from words to signs. . . Sara, the most impressive, who not only mastered grammar and vocabulary but uses them to express abstract concepts with her symbolic plastic discs. . . and intellectually curious Lana who communicates in Yerkes through a computer. An intelligent, provocative review of research whose implications are not all that easy to clarify.