Bill Poser explains why a news story about how Koko, the gorilla, used American Sign Language (ASL) to tell her caretakers that she needed a visit by the dentist tells us more about the limits of animal communication than it does about the wonders of animal communication:

Unlike many animal language stories, this one seems perfectly plausible. There is plenty of evidence that Koko and other non-human primates can learn and use symbols. In many ways, the most interesting thing about this story is what it tells us about what Koko can’t do, since her fans have often claimed that she exhibits human-like language. Koko wasn’t able to form an ASL sentence along the lines of my tooth hurts” — she used one ASL word, pain”, and pointed at her mouth. Nor was she able to express the degree of her pain in language. She couldn’t say: it hurts a lot”. To find out how bad her pain was, her handlers had to have her point at a chart. How they taught her the meaning of the chart is itself an interesting question, and we should probably be impressed that she was able to learn how to use the chart to express the extent of her pain, if that is indeed what she did. But the linguistic point here is that, although Koko is able to use symbols, her linguistic ability is quite different from that of a human being. She has no grammatical structure and cannot form sentences. She cannot even express, using words alone, simple things like: my tooth hurts” or it hurts a lot”, which any normal human three-year can manage quite nicely.

I always felt that it was a big mistake to make too much of animal communication. Isn’t it enough that they communicate? Why do we have to claim that their communication is the same as human language” in order to give animals their due? Anyone whose ever had a pet knows how communicative animals can be. I think there can be no doubt that most mammals have some kind of intelligence, even if it isn’t the same as human intelligence. As Justice Oliver Wendell Holmes once said, Even a dog distinguishes between being stumbled over and being kicked.” It shouldn’t be necessary to claim that a dog speaks English in order to remove the even” from that sentence!