Koko the gorilla, whose remarkable sign-language ability and motherly attachment to pet cats helped change the world’s views about the intelligence of animals and their capacity for empathy, has died at 46. Koko was taught sign language from an early age as a scientific test subject and eventually learned more than 1,000 words, a vocabulary similar to that of a human toddler. She became a celebrity who played with the likes of William Shatner, Sting, Leonardo DiCaprio, Robin Williams and Mr. Rog