About the same time as the Gardeners' studies, David Premack (1971) attempted a study with his chimpanzee, Sarah.  This study differed greatly from the Gardeners' study as Sarah was taught to use plastic chips of various shapes and colours to communicate.  Each word had a specific linguistic function.  Sarah mastered 130 terms with 75 - 80% accuracy in tests.  Terms included nouns, adjectives, verbs, prepositions, the means of indicting negative and interrogative sentences, describing dimensional classes and expressing the conditional. Premack believed he could break down the components of our language in such a way that even non humans would be able to learn it with some competence. (1)
One drawback to the Sarah experiment, was that she was not allowed to talk spontaneously but only in response to her trainers. There was the possibility that her trainers may have unknowingly provided her with cues which she responded to rather than the plastic chips. (2)
 
 
 

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(1) Progress in Ape Research pg. 78
(2) An Introduction to Language pg. 402