Apparently, a Gorilla named Koko took a number of IQ tests and scored an average of 80, their full range of scores being 70 to 95. The test used was the Cattell Infant Intelligence Scale. I don't understand why they used an infant scale, as those are intended for infants between 2 to 30 months (source). The tests were given to Koko between 1972 and '77, and she was born in 1971. That means she was one or two years old when she got the first one, putting her in the appropriate range. When she got the last test however, she was five or six. How can the infant test be applicable at that point?