A chimp who was taught sign language has died at age 42:
http://news.nationalgeographic.com/n...himp-obit.html
There was some doubts about weather Washo fully understood their conversations, especially after a number of fakes, such as Clever Hans:
http://findarticles.com/p/articles/m...Feb/ai_6331710
But the general view was that she did:
http://www.skeptic.com/eskeptic/07-10-31.html#feature
An adult chimp has been compared to a 2-3 year old human in terms of their mental development. This really illustrates the amazing capability of the human mind - we are a wonderful species.
Nevertheless, whilst our connections to our ape relatives has been confirmed by DNA analysis, many people still think of chimps as little hairy apes like what they see on TV. The fallacy is that chimps on TV are pre-adolescents. Once they are adolescents they are much too difficult to work with. These animals are about 7 times stronger than a human, and are consequently quite dangerous.
To get a better idea of a fully grown chimp, see the attached image. The size is impressive and the physiological similarities striking.