Two rhesus primates have made monkeys out of scientists who believe that being able to count depends on language. The trained monkey's, called Rosencrantz and Macduff, also showed that they could master simple arithmetic. Columbia University psychologists, who worked with them, have demonstrated that monkeys can grasp the concept of numbers from one to nine. The research, reported by the US journal, Science, further blurs the line between humans and other animals.