Whatever you do, don, t challenge a chimpanzee named Ayumu to a number memory game.In 2007, Ayumu became famous for his lightning speed at a game that goes like this: A player views a computer screen where the numbers 1 through 9 appear briefly at once and then turn to white squares. The player then taps the squares where the numbers had been, in order from 1 to 9. People can do it. But no human competitor has ever completed the game faster or more accurately than Ayumu the chimp．For almost five years Ayumu remains undefeated.Psychologist Nicholas Humphrey of Darwin College at Cambridge University in England now thinks he knows the secret behind the chimp, s ability. Humphrey suspects Ayumu, s brain may have a condition that allows the chimp to see numbers as colors. This would mean that Ayumu may see a color glow after the number disappears. Then, instead of remembering the numbers, he remembers a sequence of colors, each associated with a number.The condition that Humphrey believes Ayumu may have is called synesthesia. Humans with synesthesia may associate numbers and letters with colors. For example, a person may see the number"5"as the color blue. Until now, scientists had assumed only humans could have synesthesia. Humphrey found the inspiration for his idea at a 2011 scientific conference. There, he heard a presentation about Ayumu's memory abilities and another talk about synesthesia. He then put the two ideas together.Not everyone is convinced that Humphrey is correct. Primatologist Tetsuro Matsuzawa of the Primate Research Institute at Kyoto University in Japan has spent decades studying the amazing memories of chimpanzees, including Ayumu. He maintains that chimps simply have faster memory recall than people.What is Ayumu famous for_____?