And interestingly, there are similarities in the calls of closely related monkeys. Just as there are often similarities in how the members of human families sound, closely related monkeys sound alike. Here, again, is an example of a finding that is critically dependent on the precise acoustical measurements and statistical analyses that today's computer technology permits. It seems that, logically, if a monkey wants others to behave a certain way by sending a correct message, then, it could be capable also of sending an incorrect or even a deceptive call if it wanted something. That's a hard question to answer, scientifically.
Monkeys make mistakes in the calls they use.
A young vervet monkey, for example, may sometimes produce an eagle alarm call in response to seeing a falling leaf. The adults don't respond to these, however, and perhaps this is one way the behavior of youngsters is shaped. There are anecdotal reports of monkeys using deceptive calls, but not many of them. For example, failing to respond to an alarm call given by a sometimes unreliable monkey when there, in fact, was a predator around might just be fatal. So, skepticism is probably more limited.