Primatologists and linguists have teamed up to figure out once and for all if monkeys have language in the way that humans do, and, if so, whether or not it is possible for us to learn how to speak monkey. Presenting their work in a series of five studies, appearing in multiple journals, the researchers conclude that monkey communication has “much simpler rules than appear in human language,” with “no complex rules of syntactic or semantic composition.” In spite of this, however, many species of monkey do use sophisticated calls that appear to have syntactic and semantic rules – some of which the study authors have managed to learn.

In one study conducted in 2014, scientists working with Campbell’s monkeys found that the structure of their calls is determined by a vital distinction between root words and suffixes. For instance, “oo” sounds are sometimes added to the ends of words to dampen or diffuse their meaning, in much the way that humans may add “ish” to the end of a word to make it seem less severe. So while the monkeys use a “hok” call to communicate the approach of a serious aerial threat like an eagle, “hok-oo” denotes a variety of generic, or “dangerous-ish”, overhead disturbances.

While this example indicates that Campbell’s monkey calls have a clearly defined structure, or morphology, another study involving titi monkeys raises some interesting questions about the presence of semantics. In other words, whether or not the meaning of individual calls can change when they are combined with other calls to form phrases.

Interestingly, titi monkeys only have two types of call, labeled as A and B calls. Yet these can be strung together in a variety of combinations that appear to have their own meanings. For instance, an “AAAA” calls denotes the presence of a predatory bird in the canopy, “ABBB” signifies a cat in the canopy, and “BBBB” means there is a cat on the ground.

^{Image: Campbell's monkeys use suffixes to alter the meanings of calls. muuraa/Shutterstock}

Additionally, Campbell monkeys only use “boom” sounds at the beginning of phrases, suggesting that there may be some clear syntactic rules defining the ways in they communicate. Since these same “boom” sounds have been observed in a number of other monkey species, all of which can be traced back to a common ancestor that lived around 2.5 million years ago, the researchers believe they can plot the evolutionary history of these linguistic characteristics.

In a statement, researcher Philippe Schlenker explained that this work has revealed that some monkey calls “have been preserved over three million years.”

Overall, the study authors insist that even though they would “love to think that monkeys have language just like humans do… we claim no such thing,” suggesting instead that monkey linguistics should not be directly compared to our own.

Regarding whether or not they have managed to learn to speak monkey, they claim that “it's sometimes said that we have found ways to 'translate' monkey utterances. That's at best a half-truth, because there is still much uncertainty about how these call systems work.”

^{Image: Titi monkey calls may be based around semantic rules. Edwin Butter/Shutterstock}