equivocal signs

SPOKANE, Wash. (AP) - Washoe, a female chimpanzee said to be the first non-human to acquire human language, has died at the age of 42 at Central Washington University. . ..

Washoe had a reported vocabulary of about 250 words. She taught sign language to three younger chimps who remain at the institute, CWU spokeswoman Becky Watson said. They are Tatu, 31, Loulis, 29, and Dar, 31. . ..

For Washoe to be considered "reliable" on a sign, it had to be seen by three different observers in three separate instances. Then it had to be seen 15 days in a row to be added to her sign list.

But claims about Washoe's language skills were disputed by scientists who believed that language is unique to humans. Among those who doubted that chimps could use language were MIT linguist Noam Chomsky and Harvard scientist Steven Pinker.

• Chomsky contended that the neural requirements for language developed in humans after the evolutionary split between humans and primates.
• Pinker contended that primates simply learn to perform certain acts in order to receive rewards, and do not acquire true language.

So, evident intelligibility, along with uncertainty that this should be understood to be language.