Koko, the adored gorilla known for her sign language skills, has died at the age of 46. Koko rose to fame in the 1970s when an animal psychologist named Francine "Penny" Patterson taught her how to communicate. She graced the cover of National Geographic twice and understood about 2,000 words of spoken English. The late Robin Williams once called his interaction with Koko "a mind-altering experience." InsideEdition.com's Keleigh Nealon (http://twitter.co.m/KeleighNealon) has more.