Recognizing that a chimpanzee was a poor candidate for spoken language learning, another scientist couple (Beatrix and Allen Gardner) set out to teach a female chimpanzee called Washoe to use a version of American Sign Language. لإhis sign language has all the essential properties of human language and is learned by many congenitally deaf children as their natural first language.

From the beginning, the Gardners and their research assistants raised Washoe like a human child in a comfortable domestic environment. Sign language was always used when Washoe was around and she was encouraged to use signs, even her own incomplete “baby-versions” of the signs used by adults. In a period of three and a half years, Washoe came to use signs for more than a hundred words, ranging from airplane, baby and banana through to window, woman and you. Even more impressive was Washoe’s ability to take these forms and combine them to produce 16 The Study of Language “sentences” of the type gimme tickle, more fruit and open food drink (to get someone to open the refrigerator). Some of the forms appear to have been inventions by Washoe, as in her novel sign for bib and in the combination water bird (referring to a swan), which would seem to indicate that her communication system had the potential for productivity. Washoe also demonstrated understanding of a much larger number of signs than she produced and was capable of holding rudimentary conversations, mainly in the form of question–answer sequences. A similar ability with sign language was reported by Francine Patterson working with a gorilla named Koko not long after.