"Koko, a lowland gorilla born in 1971, is currently the most language-proficient nonhuman, according to the Gorilla Foundation, which teaches ASL to gorillas.

The gorilla has a vocabulary of more than a thousand signs, understands about 2,000 words of spoken English, and initiates most conversations with people, according to the foundation's website.

Her IQ is between 70 and 95 on a human scale—100 is considered a 'normal' human IQ." (http://news.nationalgeographic.com/news/2011/08/pictures/110805-rise-planet-apes-movie-science-chimps-gorillas-tools/#/primate-intelligence-milestones-koko-gorilla-sign-language_38362_600x450.jpg)

So apes have the intelligence level of roughly a six year old child, they exhibit the same signs of cognitive development that we as humans do when growing up and learning. Its truly incredible.