Language in animals

Animals are obviously able to communicate in many ways. However, I remain to be convinced that any animals are able to use language. There is an important distinction between communication and language. Language is open-ended, with rules that each participant knows and understands (referred to as 'grammar' in humans), and must be intended.

There are many examples of experts who are convinced that they have observed language in animals. More often than not this refers to sign-language taught to apes (chimps, orangutans and gorillas). However, many articles are written by people with vested-interests or bias (often the trainers of the animals themselves), and therefore should perhaps be treated with caution.

I have found a number of stories on the internet about apes that have been described as using language. Here are a few summaries:

Washoe
(September 1965 – October 30, 2007) was a chimpanzee who was the first non-human to learn to use some of the signs of a human language - American Sign Language (ASL). She also passed on some of her knowledge to her adopted son, Loulis. As part of a research experiment on animal language acquisition, Washoe developed an ability to communicate with humans using ASL. She was named for Washoe County, Nevada, where she was raised and taught to use ASL. Washoe had lived at Central Washington University since 1980. She died on October 30, 2007, at the age of 42.

Chantek
Chantek the orangutan has a vocabulary of approximately 150 signs. He currently lives at Zoo Atlanta. Like children, Chantek prefers to use names rather than pronouns. He has been observed to invent signs of his own (e.g., 'eye-drink' for contact lens solution, and 'Dave missing finger' for a special friend). He developed referential ability as early as most human children, and points to and shows objects just like humans do. Chantek uses adjectives to specify attributes, such as "red bird", and "white cheese food eat", yet he overgeneralizes in interesting ways, too. For example, he uses the sign 'Lyn' for all caregivers, but never for strangers.


Nim Chimpsky
The chimpanzee Nim Chimpsky (named after linguist Noam Chomsky) was taught to communicate using sign language in studies led by Herbert S. Terrace. In 44 months Chimpsky learned 125 signs. However, linguistic analysis of his communications demonstrated that this use was symbolic, and lacked grammar, or rules, of the kind that humans use in communicating via language. This constitutes a chimpanzee vocabulary learning rate of roughly 0.1 words per day. This rate is not comparable to the average college-educated English-speaking human who learns roughly 14 words per day between ages 2 and 22.

One of the most famous signing apes was Koko the gorilla. Here is a documentary about her made in 1978. It also features Washoe the chimp. It is always impressive and moving to see animals communicating with their trainers, but I'd like to invite comments to convince me that she is really using language here. I can believe that she is able to use signs to express a need or even a feeling, but is she really able to hold a conversation in the true sense of the word?