sciencehabit (1205606) writes "It looks like a standardized test question: Is the sum of two numbers on the left or the single number on the right larger? Rhesus macaques that have been trained to associate numerical values with symbols can get the answer right, even if they haven't passed a math class. The finding doesn't just reveal a hidden talent of the animals—it also helps show how the mammalian brain encodes the values of numbers. Previous research has shown that chimpanzees can add single-digit numbers. But scientists haven’t explained exactly how, in the human or the monkey brain, numbers are being represented or this addition is being carried out. Now, a new study (abstract) helps begin to answer those questions."