Human language, on the other hand, is clearly syntactic. There are two distinct advantages to this, and one disadvantage. First, non-syntactical language does not travel well. But abstract categories such as 'jaguar' and 'slinking' can be learned separately, without direct experience of the object referred. Second, the modular nature of syntactical language means that people can shuffle words to create entirely imaginary, synthetic experiences - summarizing concepts that have never been directly experienced.
Syntactical language is therefore much more flexible than non-syntactical forms of communication.
Non-syntactical language is hamstrung by new experience. In the sentence above about jaguars and jacarandas, it is easy to substitute 'alligator' for 'jaguar' if the species of predator happens to vary. And these rules must be learned, because not every arrangement makes sense. Nowak and colleagues do not demonstrate this with the kind of vague arm-waving that has given evolutionary psychology a bad name. Rather, they discuss the relative merits of syntactical and non-syntactical language by building a mathematical model in which the advantages and disadvantages of the two forms of communication are expressed in terms of equations.