Epiphany learning is the ability of animals to use existing experience to solve current problems, including understanding, thinking and solving problems. The simplest epiphany learning is detour, that is, setting a barrier between animals and food, and animals must bypass the barrier to get close to food. Octopus can't solve this problem. Fish and birds can succeed after many attempts. Mammals (such as squirrels, mice and raccoons) can quickly learn to solve this problem. (Note: Octopus is not a fish, but a mollusk. Chimpanzees are the animals with the strongest epiphany learning ability except humans, and the research on the epiphany learning ability of chimpanzees was first completed by W.Kohler in the 1920s. Later, more and more complicated experiments further confirmed that chimpanzees have strong insight learning ability, even approaching human ability in solving some difficult problems.