The claim that Washoe acquired language, with all its grammatical rules and structures, is not without controversy, but it is reported that she used from 200-250 signs reliably.
Interestingly, the great ape thought to be the most adept at human language is Kanzi, a Bonobo living at the Great Ape Trust in Iowa. The Trust relates that:
Kanzi has been presented with a variety of carefully controlled tests which demonstrate his comprehension of speech. In these tests, spoken words are presented through headphones and Kanzi is requested to indicate the real object, the photo or the lexigram that the word represents. He is essentially 100 percent accurate on all words that are a part of vocabulary at any given age. Today, his vocabulary includes more than 500 words! His comprehension of spoken language is at least equivalent to that of a two-and-a-half-year-old child.It should also be noted that Kanzi has vocalized to other apes:
[Researcher] Sue Savage-Rumbaugh has observed Kanzi in communication to his sister. In this experiment, Kanzi was kept in a separate room of the Great Ape Project and shown some yogurt. Kanzi started vocalizing the word "yogurt" in an unknown "language"; his sister, who could not see the yogurt, then pointed to the lexigram for yogurt.Whether or not the apes are mastering human language, with its intricate structures and rules, it's clear that these apes are communicating with people using human words and symbols. And it's evident that these apes have emotions, and arguably an inner life. I'm fascinated by inter-species interactions, and can you imagine this one? Imagine being the researcher as Washoe learned each new sign?
What a gift. RIP Washoe.